[NTG-pdftex] PNG inclusion progress

Hans Hagen pragma at wxs.nl
Mon Jan 10 19:27:41 CET 2005


Taco Hoekwater wrote:

> - The current code assumes that transparancy should always be used 
> whenever it is a) present and b) the pdf version allows it (PDF-1.4).
> Is this reasonable?

indeed

> - There is a similar question for 16-bit color samples (PDF-1.5)

hm, more dangerous, although we may expect users to update their viewer

> - My current code uses 1.0 for the 'screen gamma' and 0.45455 (==1/2.2) 
> for the 'assumed file gamma'.  Do these 'gamma values' need 
> parameterisation?

if possible, yes

> - My code ignores bKGD (the default background color), because otherwise 
> transparancy inclusion would be pointless. That is, unless someone would 
> want to load a transparant PNG with the background applied but without 
> transparancy?

just ignore the bg color

> - I currently ignore all color management stuff in the PNG (cHRM, sRGB, 
> iCCP chunks). I do not know enough about it at the moment, and I wonder 
> if anybody is immediately interested anyway? Besides, color management 
> would require other changes to pdftex as well, I assume?

a next version of pdftex will provide overloading of the color dict so there is 
no need to handle it; it would probably badly interfere anyway

> - (this is an unrelated question) I consider adding downsampling support 
> for PNG images, but it would need a new primitive. Something like
> \pdfoptionimageresolution ?

plus \pdfoptionimageforcebw -)

Hans



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