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0001 .. meta::
0002    :description: digiKam Image Editor Enhancement Tools
0003    :keywords: digiKam, documentation, user manual, photo management, open source, free, learn, easy, image, editor, healing, clone, lens, distortion, sharpen, blur, red, eyes, local, contrast, noise, reduction, hot, pixels, restoration, vignetting
0005 .. metadata-placeholder
0007    :authors: - digiKam Team
0009    :license: see Credits and License page for details (https://docs.digikam.org/en/credits_license.html)
0011 .. _enhancement_tools:
0013 Enhancement Tools
0014 =================
0016 .. contents::
0018 .. _enhance_lensdistortion:
0020 Lens Distortion Correction
0021 --------------------------
0023 The Lens Distortion is a tool to correct spherical lens aberrations on the photos.
0025 Barrel distortion is associated with wide angle (or minimal zoom) lenses. It causes the images to appear slightly spherical (curved outward) like a barrel. You can notice this when you have straight features close to the image's peripheral sides. Pincushion distortion is the opposite defect and is associated with Telephoto lenses (maximum zoom) or underwater images. The images appear pinched (bent inward) toward the center. The Pincushion is often less noticeable than barrel but are equally visible near the edges. These distortions can easily be eliminated without visible loss in quality with this tool.
0027 .. note::
0029     This tool treats the geometrical distortions. Chromatic aberrations will not be corrected by this tool. See the **Lens Auto Correction** tool instead.
0031 The following figures explain the main types of geometrical distortions:
0033     (1): Pincushion distortion.
0035     (2): No distortion.
0037     (3): Barrel distortion.
0039 .. figure:: images/editor_geometrical_distortions.webp
0040     :alt:
0041     :align: center
0043     The Geometrical Distortion Types
0045 .. note::
0047     A bit of explanation first. The geometrical corrections use 4th-order polynomial coefficients:
0049         - The 1st-order coefficient changes the size of the image. The tool calls this **Zoom**.
0051         - The 2nd-order coefficient treats the main geometrical distortion of lenses and can correct the convex or concave shape of the image.
0053         - The 3rd-order coefficient has a similar rounding effect but levels off towards the edges. This correction is not employed in the tool.
0055         - The 4th-order coefficient corrects the far edges inversely to the 2nd-order rounding. Combining it with the 2nd-order correction the geometrical distortions can be almost completely eliminated.
0057 .. figure:: images/editor_lens_distortion.webp
0058     :alt:
0059     :align: center
0061     The Image Editor Lens Distortion Tool
0063 Four sliders let you set the distortion correction filter:
0065     - **Main**: this value controls the amount of 2nd-order distortion. Negative values correct barrel distortions, while positive values correct pincushion distortion.
0067     - **Edge**: this value controls the amount of 4th-order distortion. The Edge control has more effect at the edges of the image than at the center. For most lenses, the **Edge** parameter has the opposite sign of the **Main** parameter.
0069     - **Zoom**: this value rescales the overall image size (1st-order correction). Negative values zoom out of the image, while positive values zoom in.
0071     - **Brighten**: this control adjusts the brightness in image corners. Negative values decrease the brightness image corners, while positive values increase it.
0073 To help you to choose the best filter settings, the widget dialog illustrates with a thumbnail preview the distortion correction applied to a crossed mesh pattern. The values you apply to your image will be saved and come up with the same values as default the next time you call the tool.
0075 .. note::
0077     The barrel-pincushion correction should be done before any crop or size changes (including perspective correction). In fact the Barrel-Pincushion corrections should be the very first step on the original image. If you crop the image and then use barrel correction the effect would be obviously wrong.
0079 To help you finding the best correction the tool provides a vertical and horizontal guide. Move the mouse cursor in the image preview to display the dashed lines guide. Move the cursor to an important place in the image like the sea level or a building border and press the left mouse button for freeze the dashed lines position. Now, adjust the barrel/pincushion correction to align with the guide.
0081 When using pincushion correction the resulting image will have a black border in the corner. You will need to cut this out with a crop tool available in :menuselection:`Transform --> Crop` Image Editor menu or via the zoom slider of this dialog.
0083 On most images using the barrel correction is enough, however with some shots such as front images, frames, paintings, the next logical step is to use perspective correction to make all the angles 90 degrees. Note that when you hold your camera by hand you almost always introduce some kind of slight perspective distortion.
0085 .. _enhance_vignetting:
0087 Vignetting Correction
0088 ---------------------
0090 Overview
0091 ~~~~~~~~
0093 digiKam The Vignetting correction is a tool to correct image vignetting (under-exposure in the corners).
0095 Wide angle lenses, especially those used in medium and large format photography, frequently do not uniformly illuminate the entire sensor plane. Instead, they *vignette* (shade) the edges and corners of the image, substantially reducing the light reaching the sensor there. But telelenses may show vignetting too.
0097 The traditional solution for this is to attach a *center filter* to the lens. This is a neutral density filter with maximum density at the optical axis of the lens, clear at the periphery, with density varying inversely to the vignetting of the lens. A center filter has many advantages: not only does it automatically correct for full-frame images but, since it's fixed to the front of the lens, it also compensates for the off-center vignetting which occurs when camera movements are employed for perspective or plane of focus adjustment.
0099 But there are disadvantages as well. Many center filters require a 1.5 or 2 f-stop filter factor adjustment, which may in turn necessitate a shutter speed so slow (since wide angle lenses, even with center filters, are best used at apertures of f/16 or smaller) that hand-holding the camera is impossible and motion blur becomes a problem when photographing moving objects.
0101 With the wide exposure range of present-day film and the color (or grey-scale) depth of digital camera or film scanners, it is possible to simulate the effect of a center filter by applying an equivalent transform to a raw image taken without the filter.
0103 Using the vignetting correction tool
0104 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
0106 .. figure:: images/editor_vignetting_correction.webp
0107     :alt:
0108     :align: center
0110     The Vignetting Correction Types
0112 Five sliders give you control over the vignetting correction filter, and three more over the target image exposure:
0114     - **Amount**: this option controls the degree of luminosity attenuation by the filter at its point of maximum amount. The default amount is 2.0, which corresponds to an optical filter with a 1 f-stop filter factor (or, by no coincidence, a factor of 2 in luminosity). Increase the amount to compensate for a greater degree of vignetting; reduce it for less.
0116     - **Feather**: this option determines the rate at which the filter intensity falls off from the point of maximum amount toward the edges, expressed as a power factor. The default of 1 yields a linear reduction in filter amount with distance from the center. Power factors greater than 1.0 cause a faster fall-off (for example, a power of 2 causes the amount to decrease as the square of the distance from the center) and causes the effect of the filter to be concentrated near the center. Powers less than 1 spread out the amount of the filter toward the edges; a power of 0.5 causes the amount to fall as the square root of the distance from the center.
0118     - **Radius**: this option specifies the radius, as a multiple of the half diagonal measure of the image, at which the amount of the filter falls off to zero (or, in other words, becomes transparent). The default value of 1.0 specifies a filter which is transparent at its corners. A radius specification greater than 1 extends the effect of the center filter beyond the edges of the image, while a radius less than one limits the filter's action to a region smaller than the image. When compensating for vignetting by lenses used with large format and some medium format cameras, the default radius factor of 1 is rarely correct! These lenses often "cover" an image circle substantially larger than the film to permit camera movements to control perspective and focus, and consequently have a vignetting pattern which extends well beyond the edges of the film, requiring a radius setting greater than 1 to simulate a center filter covering the entire image circle.
0120     - **X offset** and **Y offset** settings: these options moves respectively the center of the filter horizontally or vertically up to the border of the image by the specified percentage. A negative value for the X offset will shift the filter to the left while a positive value will shift it to the right. A negative value for the Y offset will move the filter up, and finally a positive value will move it down.
0122     - **Add Vignetting**: many photographs looks flat because of a distracting background or another composition matter. While most of time you will want to remove vignetting it is a fact that a selective vignetting could improve the readability of a photograph and draw the eyes to the intended subject. As an artist you may choose this option, ticking it will invert the filter thus darkening the corners of a photograph.
0124 The only way to be sure which settings of **Amount**, **Feather**, and **Radius** best compensate for the actual optical characteristics of a given lens is to expose a uniformly illuminated scene (for example, a grey card lit by diffuse light) and perform densitometry on the resulting image (for example with Adjust Level tool histogram position bar). Failing that, or specifications by the lens manufacturer giving the precise degree of vignetting at one or more working apertures, you may have to experiment with different settings to find those which work best for each of your lenses. For help you in this task, the widget dialog provide a thumbnail mask rendering applied on the image. Fortunately, the response of the human eye is logarithmic, not linear like most digital imaging sensors, so you needn't precisely compensate for the actual vignetting to create images which viewers will perceive as uniformly illuminated.
0126 .. note::
0128     If you want a finer exposure re-adjustment of the target image, use the Adjust Curve tool from Image Editor available under :menuselection:`Color --> Adjust Curve` menu entry.
0130 The vignetting correction tool in action
0131 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
0133 This is an example of an anti vignetting correction applied to an image. The original image on the top shows vignetting in the corners, the corrected image on the bottom much less. The values used for this example are:
0135     - Density = 2.6.
0137     - Power = 0.9.
0139     - Radius = 1.1.
0141 .. figure:: images/editor_antivignetting_preview.webp
0142     :alt:
0143     :align: center
0145     The Image Editor Anti-Vignetting Tool
0147 .. _enhance_lensauto:
0149 Lens Auto Correction
0150 --------------------
0152 No lens is optically perfect. Even the most expensive lenses have there own imperfections, however digiKam can correct lens imperfections such as **Distortion**, **Chromatic aberration**, **Vignetting**, and **Geometry**.
0154 .. figure:: images/editor_lens_auto.webp
0155     :alt:
0156     :align: center
0158     The Lens Auto-Correction Tool from digiKam Image Editor
0160 From Image Editor go to :menuselection:`Enhance --> Lens --> Auto Corrections` menu entry to start the automatic lens correction tool. This feature uses lens data from the `Lensfun library <https://lensfun.github.io/>`_ and it has a very much up to date database of lenses which are available. It has more than a hundred lenses in its current databases. It also uses the **Metadata** from the image to find-out which lens is used.
0162 If the exact used to take the picture is available it will mention that it matches with the metadata (annoted in **Green**), however if the exact match is not available it will choose the settings from the most closes match (annoted in **Orange**). In this case it also allows users to select the lens themselves. If metadata do not match at all, it will be annoted in **Red**.
0164 .. figure:: images/editor_lens_auto_metadata_match.webp
0165    :alt:
0166    :align: center
0168    Metadata Match with LensFun Database
0170 .. figure:: images/editor_lens_auto_metadata_partial.webp
0171    :alt:
0172    :align: center
0174    Metadata Match Partially with LensFun Database
0176 .. figure:: images/editor_lens_auto_metadata_none.webp
0177    :alt:
0178    :align: center
0180    Metadata do not Match with LensFun Database
0182 You can either enable or disable the helper **Grid** lines to visualise how the geometrical distortion are corrected on image.
0184 .. figure:: images/editor_lens_auto_grid.webp
0185     :alt:
0186     :align: center
0188     The Lens Auto-Correction Tool Displaying the Helper Grid over the Canvas
0190 Select the corrections you want to apply move you mouse inwards and outwards of the preview window which will show you before and after. When you are satisfied with the result press **OK**.
0192 .. _enhance_hotpixels:
0194 Hot Pixels Correction
0195 ---------------------
0197 Overview
0198 ~~~~~~~~
0200 digiKam The Hot Pixels tool facilitates removing hot pixels from photographs taken with a camera electronic sensor.
0202 Most current digital cameras produce images with several brightly colored **Bad Pixels** when using slow shutter speeds. Night images can be ruined by these Bad Pixels. There are three different types of Bad Pixels:
0204     - **Stuck pixels**: it's a pixel that always reads high or is always on to maximum power on all exposures. This produces a bright pixel usually of red, blue or green color in the final image. A stuck pixel will occur regardless of shutter speed, aperture size or any other user settings. It will occur on a normal exposure and tends to be more obvious under bright condition.
0206     - **Dead pixels**: it's a pixel that reads zero or is always off on all exposures. This state produces a black pixel in the final image. Similar to stuck pixel, a dead pixel will occur regardless of shutter speed, aperture size or any other user settings.
0208     - **Hot pixels**: it's a pixel that reads high (bright) on longer exposures as white, red, or green color. The longer the exposure time, the more visible hot pixels will become. These pixels will not be visible in bright conditions.
0210 Note that stuck or dead pixels will occur at the same location for all images. If the location of the stuck or dead pixel occurs at different locations, it may be a Hot Pixel.
0212 Stuck, dead or hot pixels are a problem in particular when shooting in high quality raw mode since many cameras have built-in hot pixel suppression applied automatically when JPEG compression is used (which is mostly the case).
0214 This tool can be used to fix the **Hot pixels** and **Stuck Pixels** on a photograph using a **Black Frame** subtraction method. There is not a manual editor to select Bad Pixels.
0216 Create the Black Frames
0217 ~~~~~~~~~~~~~~~~~~~~~~~
0219 The Black Frame subtraction method is the most accurate "Hot Pixels" and "Stuck Pixels" removal. First you have to create a "Black Frame" as a reference. This is easy to do. When you finish taking your long exposure shots, put a lens cap on the camera and take one "dark" image with the same exposure time as the images before. This image will be all dark, but with close examination you will see that it has the Hot and Stuck Pixels (colored dots). These are positioned at the same places as on your previous shots.
0221 Load this file to the widget using the **Black Frame** button. The tool will process an automatic detection of Hot and Stuck Pixels. They will be highlighted in the control panel preview areas.
0223 .. warning::
0225     If you use an old digital camera, it is important to re-shoot the Black Frame next time you are taking a long exposure images to detect new Hot and Stuck Pixels on sensor defects.
0227 Using the Hotpixel Tool
0228 ~~~~~~~~~~~~~~~~~~~~~~~
0230 .. figure:: images/editor_hotpixels_fixer.webp
0231     :alt:
0232     :align: center
0234     The Image Editor Hot Pixels Tool
0236 At first, as explained in the previous section, you need to load a Black Frame corresponding to the image to correct. An automatic parsing will be processed on the Black Frame to find bad pixels. Note that the widget will remember the previous Black Frame used on the last session and it will be re-opened automatically with the next session.
0238 The image panel and the original preview help you to pan within the image. The preview window shows the filter output using the current settings. Bad Pixels are highlighted on preview area.
0240 Select an area to see bad pixels on preview and the filter result using *Separate View* options of image panel. Choose the best **Filter** method to interpolate pixels or pixel blocks. These are the available filters:
0242     - **Average**: the pixels adjacent to the pixel block are averaged. The resulting color is assigned to all pixels in the block. For 1-dimensional interpolation, this is done separately for one pixel-wide, horizontal or vertical stripes.
0244     - **Linear**: the pixels which have a distance of 1 from the pixel block are used to calculate a bi-linear surface (2-dim), or a group of linear curves (1-dim), which is then used to assign interpolated colors to the pixels in the block.
0246     - **Quadratic**: this is the default filtering method. The pixels which have a distance of 2 or less from the pixel block are used to calculate a bi-quadratic surface (2-dim), or a group of quadratic curves (1-dim), which is then used to assign interpolated colors to the pixels in the block.
0248     - **Cubic**: the pixels which have a distance of 3 or less from the pixel block are used to calculate a bi-cubic surface (2-dim), or a group of cubic curves (1-dim), which is then used to assign interpolated colors to the pixels in the block.
0250 .. _enhance_localcontrast:
0252 Local Contrast Tool
0253 -------------------
0255 The Local Contrast tool render pseudo-HDR image.
0257 There are multiple ways to render HDR image to improve photos containing under or overexposed areas. With camera devices, usual tools let you merge multiple shots with different exposures into one perfectly exposed photo. This work nicely but require some limitation, as for example the necessity to shot static subjects. But what if you have just in case of single image, or with dynamic subjects? You might want to give a try to the Local Contrast feature. It uses a Low Dynamic Range `Tonemapping <https://en.wikipedia.org/wiki/Tone_mapping>`_ which is designed to improve the dynamic range of the photo by reducing its global contrast and increasing the local contrast. It does so by generating a desaturated and blurred version of the photo. It then combines the RGB channels of the original photo with the desaturated blurred image using either the Linear or Power function. Sounds complicated? Don’t worry, the Local Contrast tool is rather straightforward to use, so you don’t have to understand all its intricacies in order to achieve pleasing results.
0259 .. figure:: images/editor_local_contrast.webp
0260     :alt:
0261     :align: center
0263     The Image Editor Local Contrast Tool
0265 Open the photo you want in the editor and choose :menuselection:`Enhance --> Local Contrast`. The tool lets you apply up to four tonemapping operations called stages. Each **Stage** offers two parameters for you to tweak: **Power** and **Blur**. The former allows you to specify the desaturation level, while the latter lets you adjust the affected areas on the photo. To preview the result, hit the **Try** button. Once you are satisfied with the result, press **OK** to apply the process to the photo.
0267 While the Local Contrast tool may sound like an easy way to fix photos, you should use it with care: sometimes it can do more damage than good, producing unnaturally looking photos.
0269 .. _enhance_nr:
0271 Noise Reduction
0272 ---------------
0274 digiKam The Noise Reduction is a powerful tool to reduce the image noise.
0276 This tool provides selectable image filters to remove specks or other artifacts caused by junk such as dust or hair on the lens. It also can be used to remove Sensor Noise from the camera that maybe caused by high ISO settings, as well as the so-called Moiré Patterns on scanned images from books or magazines.
0278 If you want more information about what's digital camera sensor noise, please take a look in `this tutorial <https://www.cambridgeincolour.com/tutorials/image-noise.htm/>`_.
0280 .. figure:: images/editor_noise_reduction.webp
0281     :alt:
0282     :align: center
0284     The Image Editor Noise Reduction Tool
0286 The above screenshot shows a typical scene taken with an digital camera using a high sensitivity ISO setting. It shows grainy noise which can be reduced successfully with this tool.
0288 The re-sizeable image panel with the original preview helps you to pan within the image. Move the red rectangle around to select the area that lets you judge on the optimal filter settings. The preview window shows the filter output using the current settings. It can be rearranged in four different combinations as depicted in the icons below the original preview. This screenshot shows the first arrangement where the same cutout is shown for comparison. On the bottom of preview area, you can see **Zoom Factor** settings to magnify an area of the image.
0290 You can see below a full description of all parameters:
0292     - **Estimate Noise**: compute automatically all noise reduction settings by a parse of noise contained in image. By default it recommended to turn on this option and check the result. If reduction of noise is not enough efficient or damage the image, turn off this option, and adjust the **Luminance**, **Chrominance Blue**, and **Chrominance Red** settings manually.
0294     - **Threshold**: use the slider for coarse adjustment, and the spin control for fine adjustment. The threshold is the value below which everything is considered noise. This value should be set so that edges and details are clearly visible and noise is smoothed out. These settings exists for the **Luminance**, **Chrominance Blue**, and **Chrominance Red** channels. Simply adjust it and watch the preview. Adjustment must be made carefully, because the gap between noisy, smooth, and blur is very small. Adjust it as carefully as you would adjust the focus of a camera.
0296     - **Softness**: use the slider for coarse adjustment, and the spin control for fine adjustment. The softness adjusts the level of the thresholding (soft as opposed to hard thresholding). The higher the softness the more noise remains in the image. These settings exists for the **Luminance**, **Chrominance Blue**, and **Chrominance Red** channels. Simply adjust it and watch the preview. As for the Threshold settings, adjustment must be made carefully, because the gap between noisy, smooth, and blur is very small. Adjust it as carefully as you would adjust the focus of a camera.
0298     - **Save As** and **Load**: these buttons are used to do just that. Any Noise Reduction parameters that you have set can be saved to the filesystem and loaded later.
0300     - **Defaults**: this button resets all settings to default values.
0302 .. _enhance_blur:
0304 Blur Tool
0305 ---------
0307 The Blur Tool is dedicated to soft an image.
0309 Sometimes an image is too crisp for your purposes. The solution is to blur it a bit: fortunately blurring an image is much easier than sharpening it. Select the **Blur Tool** with the :menuselection:`Enhance --> Blur` menu entry and experiment with the level. The preview window on the right of the dialog shows the effect of the operation on your photograph.
0311 .. figure:: images/editor_blur.webp
0312     :alt:
0313     :align: center
0315     The Image Editor Blur Tool
0317 .. _enhance_restoration:
0319 Photograph Restoration
0320 ----------------------
0322 digiKam The Photograph Restoration is definitely one of the most advanced tools to reduce photograph artifacts.
0324 This fantastic restoration filter is a development providing unprecedented possibilities in the public domain to remove lots of unwanted stuff from your images. It is well adapted to deal with degraded images suffering from Gaussian noise, film grain, scratches or compression artifacts and local degradations usually encountered in digital (original or digitized) images. The smoothing happens along the image curvatures, thus preserving the meaningful content much alike our human eye would want it.
0326 .. figure:: images/editor_restoration.webp
0327     :alt:
0328     :align: center
0330     The Image Editor Restoration Tool
0332 The tool comes with several presets as starting points and to simplify the restoration. The preset settings available are listed below:
0334     - **None**: Using most common default filter settings not optimized for any particular purpose.
0336     - **Reduce Uniform Noise**: Optimum settings for image noise due to sensors.
0338     - **Reduce JPEG Artifacts**: JPEG's compression is not perfect, in fact for some types of images it is far from it. As a lossy compression algorithm, there are some compression "artifacts" - slight defaults showing in the decompressed image. This setting aims at correcting this problem.
0340     - **Reduce Texturing**: Optimized to remove artifacts from scanning, digitizing or Moire patterns.
0342 If you want to set filter parameters for finer adjustments, use **General** and **Advanced Settings** tabs:
0344     .. figure:: images/editor_restoration_settings1.webp
0345         :alt:
0346         :align: center
0348         The Image Editor Restoration Tool Preset Settings
0350     - **Detail Preservation** p [0, 100]: this controls the preservation of the curvatures (features). A low value forces an equal smoothing across the image, whereas bigger values preferably smooth the homogeneous regions and leaves the details sharper. A value of 0.9 should well preserve details so that no sharpening is required afterwards. Note that **Detail Preservation** must be always inferior to **Anisotropy**.
0352     - **Anisotropy alpha** [0, 100]: a low value smooths equally in all directions, whereas a value close to 1 smooths in one direction only. If you have film grain or CCD kind of noise a high value will result in wave-like pattern, whereas JPEG artifacts are suited for values close to 1.
0354     - **Smoothing** [0, 500]: this sets the maximum overall smoothing factor (when p defines the relative smoothing). Set it according to the noise level.
0356     - **Regularity** [0, 100]: this parameter is concerned with the uniformity of the smoothing. Imagine the smoothing process as a combing of the image. Then the Regularity would correspond to the size of the comb. The bigger this value, the more even the overall smoothing will be. This is necessary when much noise is present since it is then difficult to estimate the local geometry. Also if you want to achieve a 'van Gogh' turbulence effect, setting it higher than 3 is recommended.
0358     - **Filter Iterations**: number of times the blurring algorithm is applied. Usually 1 or 2 is sufficient.
0360     .. figure:: images/editor_restoration_settings2.webp
0361         :alt:
0362         :align: center
0364         The Image Editor Restoration Tool Advanced Settings
0366     - **Angular Step** da [5, 90]: angular integration of the anisotropy alpha. If alpha is chosen small, da should also be chosen small. But beware, small angles result in long runs! Choose it as large as you can accept.
0368     - **Integral Step** [0.1, 10]: spatial integration step width in terms of pixels. Should remain less than 1 (sub-pixel smoothing) and never be higher than 2.
0370     - **Use Linear Interpolation**: The gain in quality if you select this option is only marginal and you lose a factor of 2 in speed. Our recommendation is to leave it off.
0372 **Save As** and **Load** buttons are used to do just that. Any Photograph Restoration filter settings that you have set can be saved to the filesystem in a text file and loaded later.
0374 .. warning::
0376     Photograph restoration is (comparatively) very fast in what it is doing, but it can take a long time to run and cause high CPU load. You may always abort computation by pressing **Abort** button during preview rendering.
0378 .. _enhance_redeyes:
0380 Remove Red Eyes
0381 ---------------
0383 Red eyes are caused when the camera flashlight is used to take photographs of people. The red is the reflection from the back of the eye which can be seen because the pupil cannot react quickly enough to the flash. By the way, with a separate flash light the red eye effect is less likely because of the different viewing angle of flash and lens. You can correct some of the worst effect of Red Eye by selecting the area of the eye on the photograph, in the same way as described for cropping above. Then select :menuselection:`Enhance --> Red Eye Reduction`.
0385 How it works
0387     - Set the preview mode to your liking. Adjust region of image to the eyes of face to fix.
0389     - A neural network engine parse the image contents to localize automatically eyes and the red pupils.
0391     - The **Red Level** setting adjusts the amount of red eyes removal, in aggressive mode or not.
0393 .. figure:: images/editor_redeyes_correction.webp
0394     :alt:
0395     :align: center
0397     The Image Editor Red Eyes Removal
0399 .. _enhance_sharpen:
0401 Image Sharpening
0402 ----------------
0404 Overview
0405 ~~~~~~~~
0407 digiKam provides three different tools for sharpening, with each having merits in a different area.
0409     - **Simple Sharp** is a traditional sharpening tool, which is very fast and easy, but may quickly produce grainy images, in particular in dark areas.
0411     - **Unsharp Mask** works on the edge contrast to make an image appear sharper, but it actually does not sharpen at all, it works rather psychovisually. It can be used to remove atmospheric haze, and here it does a real good job. The algorithm was taken from the Gimp, and it is copyrighted by Winston Chang.
0413     - **Refocus** is probably the best of the three because it actually improves sharpness. It is a bit more involved in its application as is has several parameters to play with. 
0415 Out-of-focus photographs, as well as most digitized images, need correction of sharpness. This is due to the digitizing process that must chop up a color continuum in points with slightly different colors: elements thinner than sampling frequency will be averaged into an uniform color. Thus, sharp borders are rendered a little blurred. The same phenomenon appears when printing color dots on paper. SLR cameras need even more sharpening on a regular basis than consumer cameras.
0417 Whereas JPEG images have some camera-internal sharpening applied, RAW format images always need sharpening in their workflow.
0419 Some scanners apply a sharpen filter while scanning. It's worth to disable it so that you keep control over your image.
0421 Adjusting Sharpness
0422 ~~~~~~~~~~~~~~~~~~~
0424 If the camera focus is not set perfectly or if the camera is moving when the image is taken the result is a blurred photograph. If there is a lot of blurring, you probably will not be able to do much about it with any technique. If there is only a moderate amount, you should be able to improve the image. Many good SLR cameras apply less image processing to the images than simpler cameras (which tend to artificially increase the contrast to make the images look crisp). This kind of slight blur can be easily improved with tools.
0426 In some situations, you may be able to get useful results by sharpening an photograph using the Sharpen tool by the :menuselection:`Enhance --> Sharpen` menu entry and the **Sharpen** option from **Method** setting.
0428 .. figure:: images/editor_sharpen.webp
0429     :alt:
0430     :align: center
0432     The Image Editor Sharpen Tool
0434 You should be careful with this though, or the results will not look very natural: sharpening increases the apparent sharpness of edges in the photograph, but also amplifies noise. Generally, the most useful technique for sharpening a fuzzy photograph is the Refocus tool. You can access it with the **Refocus** option from **Method** setting. Look at Refocus for more information and a comparison of all the sharpening techniques.
0436 Reducing Graininess In a Photograph
0437 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
0439 When you take a photograph in low-light conditions or with a very fast exposure time, the camera does not get enough data to make good estimates of the true color at each pixel, and consequently the resulting photograph looks grainy. You can "smooth out" the graininess by blurring the image, but then you will also lose sharpness. Probably the best approach - if the graininess is not too bad - is to use the filter **Noise Reduction** tool, and you can access it by the :menuselection:`Enhance --> Noise Reduction` menu entry.
0441 Softening a Photograph
0442 ~~~~~~~~~~~~~~~~~~~~~~
0444 Sometimes you have the opposite problem: an image is too crisp. The solution is to blur it a bit: fortunately blurring an image is much easier than sharpening it. Select the **Blur Tool** with the :menuselection:`Enhance --> Blur` menu entry and experiment with the level. The preview window on the right of the dialog shows the effect of the operation on your photograph.
0446 The Unsharp Mask Filter
0447 ~~~~~~~~~~~~~~~~~~~~~~~
0449 .. note::
0451     The **Unsharp Mask** filter is an excellent tool to remove haze from your photographs.
0453 .. figure:: images/editor_unsharpen_mask.webp
0454     :alt:
0455     :align: center
0457     The Image Editor Unsharpen Mask Tool
0459 The image panel and the original preview help you to pan within the image. The preview window shows the filter output using the current settings.
0461 There are two important parameters, **Radius** and **Amount**. The default values often work pretty well, so you should try them first. Increasing either the **Radius** or the **Amount** increases the strength of the effect. Don't get carried away, though: if you make the unsharp mask too strong, it will amplify noise in the image and create the impressions of ridges next to sharp edges.
0463 The **Radius** allows you to set how many pixels on either side of an edge that will be affected by sharpening. High resolution images allow higher radius. You'd better always sharpen an image at its final resolution.
0465 The **Amount** control is the percentage of the difference between the original and the blur image that is added back into the original. It allows you to set strength of sharpening.
0467 The **Threshold** control is a fraction of the maximum RGB value, needed to apply the difference amount. It allows you to set the minimum difference in pixel values that indicates an edge where sharpening should be applied. That way, you can protect areas of smooth tonal transition from sharpening, and avoid creation of blemishes in face, sky or water surface.
0469 Refocus a Photograph
0470 ~~~~~~~~~~~~~~~~~~~~
0472 The Refocus is a tool to refocus an image by enhancing the sharpness. It uses the deconvolution Filter algorithm.
0474 This tool attempts to "refocus" an image by undoing the defocussing. This is better than just trying to sharpen a photograph. It is employing a technique called FIR Wiener Filtering. The traditional technique for sharpening images is to use unsharp masking. Refocus generally produces better results than Unsharp masking. Start it from the :menuselection:`Enhance --> Sharpen` menu entry and **Refocus** option.
0476 The Refocus technique works differently from **Unsharp Mask** and is also unlike the **Sharpen** Filter which both increase the contrast of the edges of an image. Refocus rather reverses the process by which the image got blurred by the circular aperture of the camera. This method gives you as much of the original "in focus" image as possible. Refocus uses a very powerful deconvolution algorithm that will reclaim the data that has been mixed up. In mathematical terms, blurring is usually the result of a convolution, a deconvolution will reverse the process, this is exactly what Refocus is doing. Furthermore, the FIR filter technique allows to remove much of the noise and granularity that often gets accentuated in the sharpening process of all sharpening filters.
0478 .. figure:: images/editor_refocus.webp
0479     :alt:
0480     :align: center
0482     The Image Editor Refocus Tool
0484 The image panel and the original preview help you to pan within the image. The preview window shows the filter output using the current settings.
0486 In most cases (blurring by camera) a circular convolution caused the image degradation, but there are two convolutions available:
0488     - The **Circular convolution**: this one spreads each source point uniformly across a small disk with a fixed radius. Technically this describes the effects of using a (ideal) lens that is not correctly focused.
0490     - The **Gaussian convolution**: this one is mathematically similar to the normal distribution, with its bell-shaped curve. Originates rather from unnatural blurring (software blurring). From a theoretical point of view the mathematical justification for using the Gaussian convolution is that when you a apply a large number of independent random convolutions the results will always approach a Gaussian convolution.
0492 The refocus tool supports both the Circular and the Gaussian convolution plus mixtures of both.
0494 In practice, in most cases the Circular convolution works much better than the Gaussian convolution. The Gaussian convolution has a very long tail, so mathematically the result of the convolution also depends on source pixels at a large distance from the original source pixel. The FIR Wiener inverse of a Gaussian convolution in most cases is heavily influenced by source pixels at a large distances, and in most cases this produces undesirable results.
0496 To set correctly the deconvolution filter, the plug-in has the following parameters:
0498     - **Circular Sharpness**: This is the radius of the Circular convolution filter. It is the most important parameter for using the plug-in. With most images the default value of 1 should give good results. Select a higher value when your image is very blurred, but beware of producing halos.
0500     - **Correlation**: Increasing the Correlation may help reducing artifacts. The correlation can range from 0-1. Useful values are 0.5 and values close to 1, e.g. 0.95 and 0.99. Using a high value for the correlation will reduce the sharpening effect of the plug-in.
0502     - **Noise filter**: Increasing the Noise filter parameter helps reducing artifacts. The Noise can range from 0-1 but values higher than 0.1 are rarely helpful. When the Noise value is too low, e.g. 0 the image quality will be horrible. A useful value is 0.03. Using a high value for the Noise will even blur the image further.
0504     - **Gaussian Sharpness**: This is the radius for the Gaussian convolution filter. Use this parameter when your blurring is Gaussian (mostly due to previous blur filtering). In most cases you should leave this parameter to 0, because it causes nasty artifacts. When you use non-zero values you will probably have to increase the Correlation and/or Noise filter parameters, too.
0506     - **Matrix size**: This parameter determines the size of the transformation matrix. Increasing the Matrix Size may give better results, especially when you have chosen large values for Circular Sharpness or Gaussian Sharpness. Note that the plug-in will become very slow when you select large values for this parameter. In most cases you should select a value in the range 3-10.
0508     - **Save As** and **Load**: these buttons are used to do just that. Any Refocus parameters that you have set can be saved to the filesystem and loaded later.
0510     - **Defaults**: this button resets all settings to default values.
0512 Below, you can see few hints to help you work with the refocus tool:
0514     - Preferably perform all cropping, color and intensity curve corrections on the image before using this plug-in.
0516     - Otherwise use this plug-in before performing any other operations on the image. The reason is that many operations on the image will leave boundaries that are not immediately visible but that will leave nasty artifacts.
0518     - When you are scanning images and compress them, e.g. to JPEG, you should use the plug-in on the uncompressed image.
0520 Refocus Comparison with Other Techniques
0521 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
0523 Comparison to two other techniques frequently used to enhance images are:
0525     - **Simple Sharp** Filter.
0526     - **Unsharp Mask**.
0528 Sharpening applies a small convolution matrix that increases the difference between a source pixel and its immediate neighbors. FIR Wiener filtering is a more general technique because it allows a much larger neighborhood and better parameterizations. Sharpening only works when your images are very slightly blurred. Furthermore, for high values of the sharpening parameter the results frequently looks "noisy". With FIR Wiener filtering this noise can be greatly reduced by selecting higher values for the **Correlation** and **Noise filter** parameters.
0530 Unsharp masking is another very popular image enhancement technique. From a mathematical point of view its justification is a bit obscure but many people are very fond of it. The first step is to create a blurred copy of the source image. Then the difference between the source image and the blurred image is subtracted from the source image, hence the name unsharp masking. If fact, unsharp masking is more of a contrast enhancement on the important image feature than a sharpening. It does not undo the aperture pattern interference of the camera diaphragm as refocus does.
0532 In general, unsharp masking produces better results than sharpening. This is probably caused by the fact that unsharp masking uses a larger neighborhood than sharpening.
0534 From a theoretical point of view unsharp masking must always introduce artifacts. Even under optimal circumstances it can never completely undo the effect of blurring. For Wiener filtering it is possible to prove that it is the optimal linear filter. In practice, in all cases the results of the FIR Wiener filter were at least as good as those of unsharp masking. The FIR Wiener filter is frequently better in restoring small details.
0536 Below, you can see a comparison of different filter apply on a small unfocused image:
0538 .. figure:: images/editor_refocus_notsharpened.webp
0539    :width: 300px
0540    :alt:
0541    :align: center
0543    Original blurred color image to fix.
0544    This image have been taken with an analog still camera.
0545    The unfocusing result of an insufficient light for the auto-focus lens.
0547 .. figure:: images/editor_refocus_sharped.webp
0548    :width: 300px
0549    :alt:
0550    :align: center
0552    Fixed image using simple sharpening filter.
0553    Sharpness setting is 80.
0555 .. figure:: images/editor_refocus_unsharpmask.webp
0556    :width: 300px
0557    :alt:
0558    :align: center
0560    Fixed image using unsharp mask filter.
0561    Settings are: Radius=50, Amount = 5, and Threshold=0.
0563 .. figure:: images/editor_refocus_refocus.webp
0564    :width: 300px
0565    :alt:
0566    :align: center
0568    Fixed image using Refocus filter.
0569    Settings are: Circular Sharpness=1.3, Correlation=0.5,
0570    Noise Filter=0.020, Gaussian Sharpness=0 and Matrix Size=5.
0572 .. note::
0574     For more information about correction of sharpness methods used in digital imagery, you can find a technical comparison at `this url <http://www.optarc.co.uk/bialith//Research/BARclockblur.htm>`_.
0576 .. _enhance_clone:
0578 Healing Clone Tool
0579 ------------------
0581 The healing tool aims to copy pixel colors from a specific portion of the image, and paste them in another portion of the image using a brush, then apply smoothing. This helps fix artifacts in images, like unwanted spots on someone’s face that can be replaced with more clear skin from a close region of face.
0583 The tool settings view on the right side provide a toolbar with 5 buttons. From left to right:
0585     - Select Source Point.
0586     - Polygon Selection With Lasso.
0587     - Move Image.
0588     - Undo clone operation.
0589     - Redo clone operation.
0591 Below the toolbar, two sliders allows to tune the clone tool properties. First one select the **Brush Radius** to adjust the size of cloned area from the canvas. A radius of 0 has no effect, 1 and above determine the brush radius configuring the size of parts copied in the image.
0593 Second one is the amount of **Radius Blur** effect in percent applied on data cloned over the canvas. A percent of 0 has no effect, values above 0 represent a factor for mixing the destination color with source color this is done radially i.e. the inner part of the brush radius is totally from source and mixing with destination is done gradually till the outer part of the circle.
0595 .. figure:: images/editor_healing_clone.webp
0596     :alt:
0597     :align: center
0599     The Image Editor Healing Clone Tool to Remove Unwanted Artifacts
0601 To select the source of image to clone, press **S**, or the **Source selection** button from the toolbar on the top of settings view. The cursor will change to aim-shape, to let you decide the central source button where you will start cloning from.
0603 .. figure:: videos/editor_clone_spot.webp
0604     :width: 300px
0605     :alt:
0606     :align: center
0608     Screencast of Image Editor Healing Clone Fixing an Artifact with Spot Tool
0610 The tool provide also a **Lasso** and **Polygon** selector for the healing clone operations. You can either press :kbd:`L` or the **Lasso selector** button from the toolbar on the top of settings view. The cursor will change to a pen shape, and you can select discrete points as you like. The polygon edges will be drawn, you just need to press and move your mouse to complete the selection form. You don’t have to draw all the region in one time. The polygon will close on itself if you press :kbd:`L` again.
0612 Now only cloning inside the selected region will happens, cloning outside will be ignored, unless you press :kbd:`L` again or :kbd:`Esc` to deactivate the lasso mode. Once you do that, you can clone anywhere in the screen as usual. Also pressing :kbd:`Esc` while in the process of drawing the lasso polygon will cancel the lasso operation. Here is a screenshot of a lasso polygon selection, and a large portion of the image cloned inside this lasso portion. Of course pressing :kbd:`L` or :kbd:`Esc` again will remove the lasso boundary, keeping the cloned pixels in place, as expected.
0614 .. figure:: videos/editor_clone_lasso.webp
0615     :width: 600px
0616     :alt:
0617     :align: center
0619     Screencast of Image Editor Healing Clone Fixing an Area Using Lasso
0621 You can undo and redo using toolbar buttons from the toolbar on the top of settings view. Two keyboard shortcuts are assigned to the tool: :kbd:`Ctrl+Z` for undo and :kbd:`Ctrl+Shift+Z` for redo. You can undo and redo without limitation.
0623 .. _enhance_gmicqt:
0625 G'MIC-Qt Tool
0626 -------------
0628 G'MIC-Qt is 3rd-party image editing tool provided as a plug-in. It is named **G'MIC** for **GREYC’s Magic for Image Computing**, `an open-source image processing framework <https://gmic.eu/>`_. The full list of G'MIC features is long and cannot be detailed here as it comes with over than 500 interesting functions to explore. It comes with filters for changing colors, creating patterns, adding artistic touches, repairing inconsistencies in pictures, rendering shapes, and much more. The plugin is highly customizable, with the ability to set favorites and even add your own filters.
0630 G'MIC-Qt is not included in the digiKam source code. Rather, it is a 3rd-party plugin included in binary distributions of digiKam, as the Windows, macOS, and Linux bundles. It can be started from the :menuselection:`Enhance --> G'MIC-Qt` menu entry or uses the icons from Tools in Right sidebar. G’MIC-Qt can be used as you do with other filters, the main difference is that instead of opening a specific filter tab on right sidebar, it opens up a window where you can pick through any of the pre-defined filters.
0632 .. figure:: images/editor_gmicqt_dialog.webp
0633     :alt:
0634     :align: center
0636     The Image Editor G'MIC-Qt Tool Running the Artistic/Bokeh Filter
0638 The categories of **Available filters** in the list are listed below:
0640     - **About**: these entries are not filters, but just show different information about G'MIC-Qt on the settings view. The **About/Download External Data** entry allows to load new filter definitions via internet.
0642     - **Array and tiles**: this filter collection allows transforming photos as toys, puzzles, maps, and decorative shapes.
0644     .. figure:: images/editor_gmicqt_arraytiles_puzzle.webp
0645         :alt:
0646         :align: center
0648         The Image Editor G'MIC-Qt Tool Running the Array-and-Tiles/Puzzle Filter
0650     - **Artistic**: this filter collection applies great traditional effects that seek to transform a photograph into a drawing or painting.
0652     .. figure:: images/editor_gmicqt_artistic_rodilus.webp
0653         :alt:
0654         :align: center
0656         The Image Editor G'MIC-Qt Tool Running the Artistic/Rodilius Filter
0658     - **Black and White**: this filter collection is dedicated to processing images in gray-scale style, as usual to convert, process the invert to colorize, reduce the map, or simulate fusain drawing.
0660     .. figure:: images/editor_gmicqt_bw_colorize.webp
0661         :alt:
0662         :align: center
0664         The Image Editor G'MIC-Qt Tool Running the Black-and-White/Colorize Filter
0666     - **Colors**: this filter collection allows the user to define transformation functions operating in different color-spaces, apply LUTs, mix/adjust channels or correct tones by content analysis.
0668     .. figure:: images/editor_gmicqt_colors_mixerlab.webp
0669         :alt:
0670         :align: center
0672         The Image Editor G'MIC-Qt Tool Running the Colors/Mixer-Lab Filter
0674     - **Contours**: this filter collection applies the pixel's neighborhood local transformations over the whole photo.
0676     .. figure:: images/editor_gmicqt_contours_super_pixels.webp
0677         :alt:
0678         :align: center
0680         The Image Editor G'MIC-Qt Tool Running the Contours/Super-Pixels Filter
0682     - **Deformations**: this filter collection applies physical distortions to the photo.
0684     .. figure:: images/editor_gmicqt_deformations_drop_water.webp
0685         :alt:
0686         :align: center
0688         The Image Editor G'MIC-Qt Tool Running the Deformations/Drop Water Filter
0690     - **Degradations**: this filter collection reproduces photographic alterations such as blur, noise, grain, and lens aberrations.
0692     .. figure:: images/editor_gmicqt_degradations_chromatic_aberrations.webp
0693         :alt:
0694         :align: center
0696         The Image Editor G'MIC-Qt Tool Running the Degradations/Chromatic-Aberrations Filter
0698     - **Details**: this filter collection enhances the details in your photos with an armada of multi-scale enhancement algorithms to bring out details and colors of different sizes in photos.
0700     .. figure:: images/editor_gmicqt_details_mighty.webp
0701         :alt:
0702         :align: center
0704         The Image Editor G'MIC-Qt Tool Running the Details/Mighty Filter
0706     - **Frames**: one other artistic filter collection dedicated to decorating your photo with ornaments.
0708     .. figure:: images/editor_gmicqt_frames_droste.webp
0709         :alt:
0710         :align: center
0712         The Image Editor G'MIC-Qt Tool Running the Frames/Droste Filter
0714     - **Frequencies**: this filter collection is based on Fourier Transforms analysis.
0716         .. figure:: images/editor_gmicqt_frequencies_bandpass.webp
0717             :alt:
0718             :align: center
0720             The Image Editor G'MIC-Qt Tool Running the Frequencies/Bandpass Filter
0722     - **Layers**: this filter collection works on layers or export contents to separate layers. As layers are not supported by Image Editor, usage of these filters is limited. 
0724         .. figure:: images/editor_gmicqt_layers_tiles_to_layers.webp
0725             :alt:
0726             :align: center
0728             The Image Editor G'MIC-Qt Tool Running the Layers/Tiles-to-Layers Filter
0730     - **Lights and Shadows**: this filter collection allows adjustment of under-exposed and over-exposed contents from a photo. It's also possible to patch the image with a supplemental source of light.
0732         .. figure:: images/editor_gmicqt_lights_shadows_pop_shadows.webp
0733             :alt:
0734             :align: center
0736             The Image Editor G'MIC-Qt Tool Running the Lights-and-Shadows/Pop-Shadows Filter
0738     - **Patterns**: this filter collection is a set of recursive image generation methods which can produce original and interesting geometric forms.
0740         .. figure:: images/editor_gmicqt_patterns_halftone.webp
0741             :alt:
0742             :align: center
0744             The Image Editor G'MIC-Qt Tool Running the Patterns/Halftone Filter
0746     - **Renderings**: this filter collection superimposes generated artificial forms based on mathematical solutions.
0748     .. figure:: images/editor_gmicqt_rendering_lightning.webp
0749             :alt:
0750             :align: center
0752             The Image Editor G'MIC-Qt Tool Running the Rendering/Lightning Filter
0754     - **Repair**: this filter collection includes advanced algorithms to help with image noise/glitch/objects/artifacts/compression removal. This kind of filter tries to fix very challenging problems that have occupied image-processing researchers for several generations.
0756         .. figure:: images/editor_gmicqt_repair_denoise.webp
0757             :alt:
0758             :align: center
0760             The Image Editor G'MIC-Qt Tool Running the Repair/Denoise Filter based on convolutional neural networks
0762     - **Sequences**: this filters collection generates animation from photos.
0764         .. figure:: images/editor_gmicqt_sequences_3d_image_object.webp
0765             :alt:
0766             :align: center
0768             The Image Editor G'MIC-Qt Tool Running the Sequences/3D_Image-Object Filter
0770     - **Silhouettes**: this filter collection superimposes forms such as animal finger-print, icons, nature shapes, etc.
0772         .. figure:: images/editor_gmicqt_silhouettes_nature_barnsley_fern.webp
0773             :alt:
0774             :align: center
0776             The Image Editor G'MIC-Qt Tool Running the Silhouettes/Nature/Barnsley-Fern Filter
0778     - **Stereoscopic 3D**: this filter collection renders photos in relief.
0780         .. figure:: images/editor_gmicqt_stereoscopic_3d_stereo_image.webp
0781             :alt:
0782             :align: center
0784             The Image Editor G'MIC-Qt Tool Running the Stereoscopic-3D/Stereo-Image Filter
0786     - **Testing**: this filter collection groups all tools under development. Take care: these filters can be unstable and give weird effects.
0788     - **Various**: this filters collection groups tools which cannot be categorized in others collections. A G'MIC code editor can be found to create and test new filters.
0790         .. figure:: images/editor_gmicqt_various_custom_code.webp
0791             :alt:
0792             :align: center
0794             The Image Editor G'MIC-Qt Tool Running the Various/Custom-Code Filter
0796 The default layout of G'MIC-Qt is quite simple (this can be changed in the G'MIC-Qt **Settings** dialog). See below the description of each pane:
0798     - On the left, there is the preview. With some filters, the whole image is displayed, and with other filters it will be shown a 100% crop detail, depending on the kind of effect that we are going to activate.
0800     - In the middle, there is the useful search bar at the top, with a list of groups of effects below. Each group can be opened with a double click or by clicking the small arrow on the left of the name.
0802     - On the right would appear the settings of the selected filter, if we had selected one below, to confirm the changes, there are the **Apply** and the **Ok** buttons. The **Cancel** button stops all current processing and returns to the Image Editor.
0804 You can search a filter using their groups, but the fastest way to find them is to use the **Search** bar at the top of the list. If the filter categories look a bit daunting, it's possible to add the most used filters in a favorites list and to apply a color tag using the filters tree-view context menu. On the bottom, the **Add Fave** button allows appending an entry in the first section named **Faves** on the list.
0806 .. figure:: images/editor_gmicqt_filters_tree_view.webp
0807     :alt:
0808     :align: center
0810     The Image Editor G'MIC-Qt Tool Filters Tree-View and the Favorites Context Menu
0812 For mostly all the G'MIC-Qt filters you can see these behaviors:
0814     - When you render the filter on whole data from Image Editor by pressing **Apply** or **Ok** buttons, the processing time can be quite long, with many megapixels images. If the computer is not powerful enough, time to process an image can take a while. A **Progress Bar** on the bottom of the G'MIC-Qt dialog will indicate the computation progress.
0816     .. figure:: images/editor_gmicqt_progress.webp
0817         :alt:
0818         :align: center
0820         The Image Editor G'MIC-Qt Tool Progress Bar
0822     - If a filter has many parameter settings, some may not be visible; use the scroll bar to access more settings. Also, it's possible to enlarge the G'MIC-Qt dialog if necessary, or switch to **Fullscreen** with the button on the bottom.
0824     - Depending on the filter, some parameters can require many iterations on the image and increase processing time. Adjust the settings carefully, as the times can increase exponentially before seeing the result.
0826     - The filter preview can be adjusted to compare the results before and after the effect. **Preview Type** settings are available in the parameters pane.
0828     .. figure:: images/editor_gmicqt_preview_type.webp
0829         :alt:
0830         :align: center
0832         The Image Editor G'MIC-Qt Tool Preview Type Settings From the Colors/Color-Blindness Filter
0834 The **Settings** button on the bottom left will show the G'MIC-Qt configuration dialog with tree tabs:
0836     - First one is used to customize the G'MIC-Qt **Interface**, as the layout of the tool panes, the language to enable, the preview behavior, and the native dialog to use.
0838     .. figure:: images/editor_gmicqt_settings_interface.webp
0839         :alt:
0840         :align: center
0842         The Image Editor G'MIC-Qt Tool Settings/Interface Dialog Tab
0844     - Second one to set up the **Filter sources**, such as where to take filter updates and where to store them on your computer.
0846     .. figure:: images/editor_gmicqt_settings_filter_sources.webp
0847         :alt:
0848         :align: center
0850         The Image Editor G'MIC-Qt Tool Settings/Filter-Sources Dialog Tab
0852     - The last one is to tune **Other** parameters, such as when to check for online updates, and the debug verbosity on the console (useful for filter developers).
0854     .. figure:: images/editor_gmicqt_settings_other.webp
0855         :alt:
0856         :align: center
0858         The Image Editor G'MIC-Qt Tool Settings/Other Dialog Tab
0860 It's suggested to explore all the available effects in G'MIC-Qt, as you can find interesting artistic solutions for your photo. See `this online review <https://jpfleury.github.io/gfo-demos/demos/fruits-400/index.html>`_ of all G'MIC-Qt filters for details.