[texhax] Transparency or reduced saturation using Graphicx ?

[Heiko Oberdiek]

On Sun, Mar 08, 2009 at 12:54:20PM +0000, Philip TAYLOR (Ret'd) wrote:

> Interestingly, Heiko's "transparent" package
> is behaving differently depending as the image
> is raster or outline : attached are two PDF
> images, representing the same scribal notation,
> one in raster format and one in vector.
> 
> Also attach is a screenshop of the result of
> embedding these two images using :
> 
> 	\hbox spread 1 pc {\transparent {0.4}\box 0 \transparent {1.0}\hss}
> 
> from which it will be seen that the counter of
> 0202 abr-ashmos-qrusos.pdf (raster) remains pure
> white, whilst the counter of 0203 abr-ashmos-qrusos1.pdf
> (vector) becomes grey during the transparency
> process.
> 
> Heiko, are you able to cast any light on this
> behaviour, and to say whether it might be possible
> to make the two images more consistent after applying
> transparency ?

The vector image first fills the counter^1 with black color
and then it fills the counter with white:

  1 0 obj <<
  ...
  >>
  stream
  0 0 0 1 k % this is black
  ...
  f* % fill black area, it includes the counter
  0 0 0 0 k % white
  ...
  f* % fill white area
  endstream
  endobj

Replace the second fill operator "f" with "%", then
you see the image entirely black.

The transparency applies to both, the black and the white
color, the result is grey.

Yours sincerely
  Heiko <oberdiek at uni-freiburg.de>

^1 BTW: "counter" here means the hole in the middle?
        (My dictionary doesn't tell something meaningful.)