c11c5eff4f
This is a patch over MR !108 by @sandsmark. Martin has done a great job implementing support and I find it a shame not to use it. I made sure that the results are the same as the current version and fixed the problems of pixels with wrong colors with color depth grater than 8 bits. I also fixed conversion errors on mask and gray images (16/32 bits). Unfortunately the internal rendering engine of the original code is 8-bit so I always forced the output of 8-bit images to correct the problems (see image below). Since it is a plugin with a "rendering engine", the tests to seriously validate it are potentially endless (as the original version is not perfect). Errors of the original version of the MR (right) which should no longer occur: 
KImageFormats
Plugins to allow QImage to support extra file formats.
Introduction
This framework provides additional image format plugins for QtGui. As such it is not required for the compilation of any other software, but may be a runtime requirement for Qt-based software to support certain image formats.
Formats
The following image formats have read-only support:
- Animated Windows cursors (ani)
- Camera RAW images (arw, cr2, cr3, dcs, dng, ...)
- Gimp (xcf)
- Krita (kra)
- OpenEXR (exr)
- OpenRaster (ora)
- Photoshop documents (psd, psb, pdd, psdt)
- Radiance HDR (hdr)
- Sun Raster (ras)
- Quite OK Image format (qoi)
The following image formats have read and write support:
- AV1 Image File Format (AVIF)
- Encapsulated PostScript (eps)
- High Efficiency Image File Format (heif). Can be enabled with the KIMAGEFORMATS_HEIF build option.
- JPEG XL (jxl)
- Personal Computer Exchange (pcx)
- SGI images (rgb, rgba, sgi, bw)
- Softimage PIC (pic)
- Targa (tga): supports more formats than Qt's version
Contributing
See the QImageIOPlugin documentation for information on how to write a new plugin.
The main difference between this framework and the qimageformats module of Qt is the license. As such, if you write an imageformat plugin and you are willing to sign the Qt Project contributor agreement, it may be better to submit the plugin directly to the Qt Project.
Note that the imageformat plugins provided by this module also provide a desktop file. This is for the benefit of KImageIO in the KDE4 Support framework.
Duplicated Plugins
The TGA plugin supports more formats than Qt's own TGA plugin; specifically, the one provided here supports indexed, greyscale and RLE images (types 1-3 and 9-11), while Qt's plugin only supports type 2 (RGB) files.
The code for this cannot be contributed upstream directly because of licensing. If anyone were willing to write fresh code to improve Qt's TGA plugin, it would allow the TGA plugin in this framework to be removed.
License
This framework is licensed under the LGPLv2.1.
The CMake code in this framework is licensed under the BSD license.