* Adam D. Moss <[EMAIL PROTECTED]> [030311 23:38]:
> Guillermo S. Romero / Familia Romero wrote:
> >Would just antierase users be happy with layers masks? This feature is
> >ignored a lot, and I think it does the same, you hide and unhide areas
> >as you want, keeping the colour info. If yes, get rid of antierase.
> One weak reservation I have (I mention it in case no-one else has
> considered it) would be that although layer masks are fine and
> beautiful and good, and XCF files are the one true GIMP
> intermediate-save working-format and they save fine and intact,
> one day you might be handed a (for example) raw .sgi file in RGBA
> and for some reason be expected to do the resurrect-colour trick,
> but to no avail.
> I'm keen on both:
> 1) No, really, don't expect me to do that.
> 2) The situation is unlikely anyway.
> its vector outline being placed in a path.  I can't think of a
> reason for someone to be handed a foreign RGBA file known
> to not be pre-multiplied, and need to resurrect its RGB data
> (except out of curiosity).  But...

PNG files stored by GIMP (at least) have resurrectable data, 

If you've got blue compoany logo that is supposed to be used on the 
web as an image with transparency to make it blend into the background
it would make sense to make the whole image solid blue, and only store
the shape in the alpha channel.

I did some testing wrt to compressed file size using png and here are my
results (default options and compression level=9 with png), and the
results suggest that for nitpicky size optimization of PNG images one
would want to have acces to the RGB values of completly transparent

(images are at http://hnb.sourceforge.net/.files/pngtest/ )

 0_alpha_is_black.png       7526 - bytes
 0_alpha_is_blue.png            6836 - bytes

I also ran the files through pngcrush which recompresses png files by
trying various strategies, (the rgb data of pixels with alpha==0 is 

 0_alpha_is_blue_crush.png      5018 - bytes
 0_alpha_is_black_crush.png     5162 - bytes

and finally the file containing just the rgb data when the background is

 rgbdata.png                            2482 

  /V\    Øyvind Kolås,  Gjøvik University College, Norway 
  ^ ^    
Gimp-developer mailing list

Reply via email to