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0001 .. meta::
0002    :description: Image File Formats Supported by digiKam
0003    :keywords: digiKam, documentation, user manual, photo management, open source, free, learn, easy, JPEG, PNG, TIFF, PGF, RAW
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 .. _image_formats:
0013 Image Files
0014 ===========
0016 .. contents::
0018 Introduction
0019 ------------
0021 digiKam relies on a number of libraries and support packages to load and save image formats. Which image formats are available will depend on the availability of these libraries on your system and, in some cases, on the way that those libraries have been compiled. On most distributions you will find that a wide range of image formats are viewable within digiKam.
0023 This dependence on other libraries means that it is not possible to give a definitive list of all of the formats that will be available on your system. At the very least JPEG, PNG, and TIFF should be available.
0025 digiKam only displays files that are in formats that it understands. It does this by looking at the file extension on the files and checking this against a predefined list. If the file extension is in the list digiKam will show the file in the Image View, provided the appropriate library is installed. You can change the list of file extensions that digiKam will accept; see :ref:`this configuration section <mime_types_settings>` for more details.
0027 Almost all digital cameras store photographs in one of two formats: JPEG or RAW. Many cameras enable you to select which of these formats to use. A full description of these formats can be found `at the Wikipedia <https://en.wikipedia.org/wiki/Image_file_formats>`_. digiKam supports both of these formats.
0029 Still Image Compression
0030 -----------------------
0032 Image compression is the application of data compression schemes on digital images. It is done through reducing redundancy of the image data in order to be able to store or transmit data in an efficient form.
0034 Image compression can be lossy or lossless. Lossless compression methods are always preferred for their high preservation value for archival purposes before applying transformations like cropping, resizing, color corrections, etc. This is because lossy compression methods, especially when used at low bit rates, introduce compression artifacts. Lossy methods are suitable for natural images such as photos in applications where minor (sometimes imperceptible) loss of fidelity is acceptable to achieve a substantial reduction in file size. Lossy compression is good for image publishing on the Internet. 
0036 .. _image_jpeg:
0038 JPEG
0039 ----
0041 `Joint Photographic Experts Group <https://en.wikipedia.org/wiki/JPEG>`_ is a compressed format that trades some of the image quality to keep file sizes small. In fact, most cameras save their images in this format unless you specify otherwise. A JPEG image is stored using lossy compression, and you can vary the amount of compression. This allows you to choose between lower compression and higher image quality or greater compression and poorer quality. The only reason to choose higher compression is because it creates smaller files so you can store more images, and it's easier to send them by e-mail or post them on the Web. Most cameras give you two or three choices equivalent to good, better, best, although the names vary.
0043 .. _image_jpeg2000:
0045 JPEG 2000
0046 ---------
0048 `JPEG 2000 <https://en.wikipedia.org/wiki/JPEG_2000>`_ is an improvement intended to replace the older JPEG by the JPEG committee, introduced in 2000. It provides for the same compression ratio with better (smoother) results compared to JPEG. The 2000 version has the option of being lossless if so specified in the settings. It supports metadata and 12 bits color depth.
0050 .. _image_tiff:
0052 TIFF
0053 ----
0055 `Tagged Image File Format <https://en.wikipedia.org/wiki/TIFF>`_ has been widely accepted and widely supported as an image format. Commonly, TIFF may be stored by the camera in uncompressed form or using a lossless compression algorithm (Deflate). It maintains higher image quality but at the expense of much larger file sizes. Some cameras let you save your images in this format, and it is a popular format because of its lossless compression algorithm. The problem is that the format has been altered by so many people that there are now 50 or more flavors and not all are recognizable by programs.
0057 .. _image_png:
0059 PNG
0060 ---
0062 `Portable Network Graphics <https://en.wikipedia.org/wiki/Portable_Network_Graphics>`_ is an image format that was developed as a replacement for a number of older, in the 1990's widely used, image file formats. It is a lossless format like TIFF but it is much more compact and saves disk space. Although your camera is unlikely to support PNG, some people like to convert their photographs to PNG as soon as they get them on their computer. Unlike JPEG, PNG images do not lose quality every time you re-encode them after modification. digiKam fully supports PNG images and the Batch Queue Manager can convert a batch of images from any supported format to PNG (and other formats) in one step.
0064 PNG is an extensible file format for the lossless, portable, well-compressed storage of raster images. PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF. PNG is designed to work well in on-line viewing applications, such as the World Wide Web, so it is fully streamable with a progressive display option. Also, PNG can store gamma and chromaticity data for improved color matching on heterogeneous platforms. PNG supports 8 and 16 bits / colors /pixels depth. It's the perfect file format to archive your photographs.
0066 .. _image_pgf:
0068 PGF
0069 ---
0071 `Progressive Graphics File <https://en.wikipedia.org/wiki/Progressive_Graphics_File>`_ is another not so known but open file image format. Wavelet-based, it allows lossless and lossy data compression. PGF compares well with JPEG 2000 but it was developed for speed (compression/decompression) rather than to be the best at compression ratio. At the same file size a PGF file looks significantly better than a JPEG one, while remaining very good at progressive display too. Thus it should be well-suited for photo archiving and **digiKam uses this format in database to store thumbnails**.
0073 .. _image_webp:
0075 WEBP
0076 ----
0078 `Web Photo <https://en.wikipedia.org/wiki/WebP>`_ is an image file format developed by Google intended as a replacement for JPEG, PNG, and GIF file formats for the Internet uses. It supports both lossy and lossless compression as well as animation and alpha transparency. It supports metadata but colors depth is limited to 8 bits. WebP was first announced by Google in 2010 and produce files that were smaller than JPEG files for comparable image quality.
0080 .. _image_heif:
0082 HEIF
0083 ----
0085 `High Efficiency Image File Format <https://en.wikipedia.org/wiki/High_Efficiency_Image_File_Format>`_ is a container format introduced in 2015 for storing individual digital images and image sequences. The standard covers multimedia files that can also include other media streams, such as timed text, audio and video. HEIF can store images encoded with multiple coding formats, for example both SDR and HDR images. HEVC is an image and video encoding format and the default image codec used with HEIF. HEIF files containing HEVC-encoded images are also known as HEIC files. Such files require less storage space than the equivalent quality JPEG. HEIF support 12 bits color depth and metadata. This format have been adopted in 2017 to store images in Apple devices.
0087 .. _image_avif:
0089 AVIF
0090 ----
0092 `AV1 Image File Format <https://en.wikipedia.org/wiki/AVIF>`_ is an open, royalty-free image file format specification introduced in 2019 for storing images or image sequences compressed with AV1 in the HEIF container format. It competes with HEIC, which uses the same container format built upon ISOBMFF, but HEVC for compression. AVIF showed better compression efficiency than JPEG as well as better detail preservation, fewer blocking artifacts and less color bleeding around hard edges in composites of natural images, text, and graphics. AVIF support 12 bits color depth and metadata.
0094 .. _image_jxl:
0096 JXL
0097 ---
0099 `JPEG XL <https://en.wikipedia.org/wiki/JPEG_XL>`_ is a royalty-free raster-graphics file format that supports both lossy and lossless compression. It is designed to outperform existing raster formats and thus become their universal replacement.
0100 JPEG XL is particularly optimised for responsive Web environments, so that content renders well on a wide range of devices. Moreover, it includes several features that help transition from the legacy JPEG format. JPEG XL was introduced at the end of 2020. JPEG XL support 16 bits color depth and metadata.
0102 .. note::
0104     Digital still image formats supports is provided by digiKam Loader Plugins. You can see a list of available plugins in **Plugins/Image Loaders** section from Setup dialog.
0106     .. figure:: images/setup_image_loaders.webp
0107         :alt:
0108         :align: center
0110         The Image Loaders list from digiKam Setup dialog
0112 .. _image_raw:
0114 RAW
0115 ---
0117 Some, typically more expensive, cameras allow you to store images in RAW format. RAW format is not really an image standard at all. It is different for every make of camera. RAW format images contain all the data that is taken directly from the camera's image sensor before the software in the camera applies things like white balance, sharpening etc. Storing photographs in a camera's RAW format allows you to alter settings, such as white balance, after the photograph has been taken. Most professional photographers use RAW format, because it offers them maximum flexibility. The downside is that RAW image files can be very large indeed.
0119 If you want to learn more about RAW image format visit the very helpful guides `Wikipedia <https://en.wikipedia.org/wiki/Raw_image_format>`_, and `Cambridge in Colour <https://www.cambridgeincolour.com/tutorials/RAW-file-format.htm>`_. You can convert RAW format images into JPEG, PNG, or TIFF in digiKam using the :ref:`Image Editor <rawprocessing_workflow>` or the :ref:`Batch Queue Manager <raw_converter>`.
0121 digiKam supports RAW image loading only, relying on the `Libraw library <https://www.libraw.org/>`_ which is included in digiKam core and supports over **1000** RAW file formats. The table below shows a short list of camera RAW files supported by digiKam:
0123 ======================= ======================================================
0124 RAW File Format         Description
0125 ======================= ======================================================
0126 CRW, CR2, CR3           Canon digital camera RAW file formats
0127 NEF, NRW                Nikon digital camera RAW file format
0128 ORF, ORI                Olympus digital camera RAW file format
0129 RAF                     Fuji digital camera RAW file format
0130 RWL                     Leica camera RAW file format
0131 PEF, PTX                Pentax digital camera RAW file format
0132 X3F                     Sigma digital camera RAW file format
0133 DCR, KDC, DC2, K25      Kodak digital camera RAW file format
0134 SRF, SR2, ARW, MRW, MDC Sony/Minolta digital camera RAW file format
0135 RAW                     Panasonic, Casio, Leica digital camera RAW file format
0136 DNG (CS1, HDR)          Adobe RAW file format (Digital Negative), Apple ProRAW
0137 BAY                     Casio RAW (Bayer)
0138 ERF                     Epson digital camera RAW file format
0139 FFF, 3FR                Imacon/Hasselblad RAW format
0140 RW2                     Panasonic RAW file format
0141 IIQ, CAP                Phase One digital camera Raw image format
0142 RDC                     Ricoh RAW format
0143 ======================= ======================================================
0145 If you want to know if your camera RAW file is supported by digiKam, go to :menuselection:`Help --> Supported RAW Cameras` dialog for details.
0147 .. figure:: images/raw_cameras.webp
0148     :alt:
0149     :align: center
0151     List of RAW Camera Formats Supported in digiKam
0153 .. _image_others:
0155 Other Formats
0156 -------------
0158 digiKam relies on `ImageMagick <https://en.wikipedia.org/wiki/ImageMagick>`_ to support exotic still images when others modules fails to load file. This is the case for FITS astro-photo, JBIG, PhotoCD, FLIF, BPG, etc.  
0160 .. note::
0162     We recommend also to read the chapter about the **file formats used for long time archiving**, from the :ref:`Digital Asset Management section <dam_fileformats>` in this manual.