2014/1/7 Florian Breitwieser :

I am trying to create PDF/A-1b compliant documents with (pdf)LaTeX. PDF/A-1 is based on PDF v4, however unlike the former it does not allow transparency (and is very strict about all its rules).

./texk/web2c/pdftexdir/writepng.c only writes the alpha channel when pdfminorversion is >= 4, and excludes it otherwise. Eg in line 523:

/* alpha channel support */ if (fixedpdfminorversion < 4 && png_get_color_type(png_ptr(img), png_info(img)) | PNG_COLOR_MASK_ALPHA) { png_set_strip_alpha(png_ptr(img)); png_copy = false; }

Would it be feasible to add a 'notransparency' or 'pdfa1' flag to generate a no-transparency PDF 4 document?

AFAIK it's based on 1.3 (the main addition of 1.4 is transparency), so can't you just set pdfminorversion to 3? Best Martin PS: Crossposted to the pdftex-devel list