Am 27.05.2011 15:09, schrieb Hartmut Henkel:
@luigi: an ICC profile definitely breaks the <png copy> rules
The only chunks left are
IHDR PNG image header: 5900x4094, 8bits/sample, truecolor, noninterlaced IDAT PNG image data .. IDAT PNG image data IEND end-of-image marker
Mh, where is the show stopper? The compression method?
Looks like some of ConTeXt PDF/X-related settings is causing this. If I reduce the code to the pure picture, the '(PNG copy)' is triggered. Probably the active color management (default color space) is breaking the copy process here.
Sorry Hartmut, my last statement is complete BS. I made a 'blind' run in my lunch break, not inspecting the pdf. And sadly I had forgotten, that I changed the test file yesterday to use a small png test graphic instead of my big png. *brain vs. full stomach: 0:1* So the PDF/X settings have no influence on this. The big png is not 'copied'. Anyhow, this is not a serious problem and honestly I don't have that much time now. When I have some more time I will use gdb to find the failing condition in writepng.w. Will be interesting, the last time I used gdb is more than 10 years ago. Thanks for all answers so far. Regards, Peter
must be some \pdfimageapplygamma > 0, only this and the \pdfimagehicolor primitive can influence this low level stuff.
Btw, just \pdfimageapplygamma > 0 (without setting \pdfgamma and \pdfimagegamma) already changes the PNG image, since the luatex (and pdftex) internal defaults are not gamma-neutral. No idea if (and then to which value) this should be fixed.
Regards, Hartmut