I was able to find this link http://www.telegraphics.com.au/svn/psdparse/trunk/psd_zip.c and if this library works well with PSD/PSB files with compressed(zip) image data, then it is possible to use Qt's qUncompress() function since it uses zlib. Can't test it since I don't have an image file with this kind of compression, neither I can save an image in Photoshop with such compression - I am not an expert (yet) of the software.
I was able to find this link http://www.telegraphics.com.au/svn/psdparse/trunk/psd_zip.c and if this library works well with PSD/PSB files with compressed(zip) image data, then it is possible to use Qt's qUncompress() function since it uses zlib. Can't test it since I don't have an image file with this kind of compression, neither I can save an image in Photoshop with such compression - I am not an expert (yet) of the software.