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0001 .. meta:: 0002 :description: digiKam Right Sidebar Colors View 0003 :keywords: digiKam, documentation, user manual, photo management, open source, free, learn, easy, colors, histogram, icc, profile 0004 0005 .. metadata-placeholder 0006 0007 :authors: - digiKam Team 0008 0009 :license: see Credits and License page for details (https://docs.digikam.org/en/credits_license.html) 0010 0011 .. _colors_view: 0012 0013 Colors View 0014 =========== 0015 0016 .. contents:: 0017 0018 The colors sidebar has two sub tabs **Histogram** and **ICC Profile**. Here are more details about :ref:`Color Management <color_management>` 0019 0020 Histogram Viewer 0021 ~~~~~~~~~~~~~~~~ 0022 0023 The histogram for an image shows the amount of each color that is present and their different amplitudes within the image. If your photograph has a color cast you might be able to see what is wrong by looking at the histogram. 0024 0025 The Histogram Viewer shows the statistical distribution of color values in the current image. It is purely informational: nothing you do with it will cause any change to the image. If you want to perform a histogram based color correction, use for example Color Balance, Levels Adjust or Curves Adjust in the Image Editor. 0026 0027 .. figure:: images/sidebar_histogramview.webp 0028 :alt: 0029 :align: center 0030 0031 The Color View From Right Sidebar Displaying Histogram Information 0032 0033 An image can be decomposed into **Red**, **Green** and **Blue** color channels. **Alpha** channel is a Layer in the image that supports transparency (like PNG or GIF images). Each channel supports a range of intensity levels from 0 to 255 (integer valued). Thus, a black pixel is encoded by 0 on all color channels; a white pixel by 255 on all color channels. A transparent pixel is encoded by 0 on the alpha channel; an opaque pixel by 255. 0034 0035 The Histogram Viewer allows you to view each channel separately: 0036 0037 - **Luminosity**: shows the distribution of brightness values. 0038 0039 - **Red**, **Green**, **Blue**: show the distribution of intensity levels for the Red, Green, or Blue channels respectively. 0040 0041 - **Alpha**: shows the distribution of opacity levels. If the layer is completely opaque or completely transparent, the histogram will consist of a single bar on the left or right edge. 0042 0043 - **Colors**: shows the **Red**, **Green**, and **Blue** histograms superposed, so that you can see all of the color distribution information in a single view. 0044 0045 With the **Scale** option you can determine whether the histogram will be displayed using a linear or logarithmic Y axis. For images taken with a digital camera, the **Linear** mode is usually the most useful. However, for images that contain substantial areas of constant color a **Linear** histogram will often be dominated by a single bar. In this case a **Logarithmic** histogram will be more useful. 0046 0047 You can restrict the analysis of the **Statistics** field shown at the bottom of the dialog to a limited range of values if you wish. You can set the range in one of two ways: 0048 0049 - Click and drag the pointer across the histogram display area, from the lowest level to the highest level of the range you want. 0050 0051 - Use the spin button entries below the histogram area. Left entry is bottom of range and right entry is top of range. 0052 0053 The statistics shown at the bottom of the Histogram Viewer describe the distribution of channel values, restricted to the selected range. These are: 0054 0055 - The number of pixels in the image. 0056 0057 - The number whose values fall within the selected range. 0058 0059 - The mean. 0060 0061 - The standard deviation. 0062 0063 - The median of the selected histogram portion. 0064 0065 - The percentage whose values fall within the selected range. 0066 0067 - The color depth of the image. 0068 0069 - Alpha channel in the image. 0070 0071 - The source of the histogram, either **Full Image** or **Image Region** if you have selected an area of the image loaded in the Editor. 0072 0073 How To Use an Histogram 0074 ~~~~~~~~~~~~~~~~~~~~~~~ 0075 0076 Histograms are a graphical means to assess the accuracy of an image shown on the screen. The graph represents the 3 regions of the photograph brightness: 0077 0078 (1) : the shadows-tone on the left. 0079 0080 (2) : the middle-tone in the middle. 0081 0082 (3) : the highlights-tone on the right. 0083 0084 .. figure:: images/sidebar_histogramdescription.webp 0085 :alt: 0086 :align: center 0087 0088 An Image Histogram in All Colors Mode 0089 0090 The distribution of the graph, where the spikes and bulges are clustered, indicates whether the image is too dark, too bright, or well-balanced. 0091 0092 With an under exposed photograph, the histogram will have a distribution of brightness that tends to be mostly on the left of the graph. 0093 0094 .. figure:: images/sidebar_histogram_underexpo.webp 0095 :alt: 0096 :align: center 0097 0098 An Under Exposed Photograph 0099 0100 With a correctly exposed photograph, the histogram will have a distribution of brightness that will be most prominent near the center part of the graph. 0101 0102 .. figure:: images/sidebar_histogram_rightexpo.webp 0103 :alt: 0104 :align: center 0105 0106 A Correctly Exposed Photograph 0107 0108 With an over exposed photograph, the histogram will have the bulge showing the brightness distributed mostly towards the right of the graph. 0109 0110 .. figure:: images/sidebar_histogram_overexpo.webp 0111 :alt: 0112 :align: center 0113 0114 An Over Exposed Photograph 0115 0116 .. important:: Not all photographs have to exhibit this bulge in the center part of their histogram. Much depends on the subject of the photograph. In some cases, it might be appropriate for the histogram to show a peak at one end or the other, or both. 0117 0118 The histogram is a reliable way of deciding whether or not a photograph is correctly exposed. Should the histogram show an over or under exposure, an :ref:`Exposure Correction Tool <color_bcg>` should be used to fix the photograph. 0119 0120 ICC Profile Viewer 0121 ~~~~~~~~~~~~~~~~~~ 0122 0123 An ICC profile is a set of data that characterizes a color input or output device, or a color space, according to standards promulgated by the `International Color Consortium <https://en.wikipedia.org/wiki/International_Color_Consortium>`_. Profiles describe the color attributes of a particular device or viewing requirement by defining a mapping between the device source or target color space and a profile connection space. Mappings may be specified using tables, to which interpolation is applied, or through a series of parameters for transformations used in Color Management. 0124 0125 Every files used to store captured image can be profiled. Camera manufacturers provide profiles for their products, and store them in image file as extra metadata. This ICC Profile viewer allows to display the textual information and a flat graph of color space. 0126 0127 .. figure:: images/sidebar_iccprofileviewer.webp 0128 :alt: 0129 :align: center 0130 0131 0132 The Color View From Right Sidebar Displaying Color Profile Information