Zhang Weiwu <[EMAIL PROTECTED]> writes:

> Thank you Michael Schumacher for helping me on the IE transparent
> pixel problem last time.
> Now I have a question: is it possible to create a png file with
> indexed color, with transparent pixels, while still have an alpha
> channel, so that the png file display alpha channel on cool browsers
> like Mozilla, while display transparent pixels on some inferior
> browser like IE as a fall-back mechanism? If GIMP cannot do it, can it
> be done in theory?
> I know the question might be silly, because I can dig it out by
> RTFM. But I just wish a quick answer so I don't have to waste time on
> impossible things:)

The PNG file format supports it but GIMP can't create such files and I
have no idea how IE would render them

>From http://www.libpng.org/pub/png/pngintro.html:

  But PNG supports alpha information with palette images as well; it's
  just slightly harder to implement in a smart way. A PNG
  alpha-palette image is just that: an image whose palette also has
  alpha information associated with it, not a palette image with a
  full alpha mask. In other words, each pixel corresponds to an entry
  in the palette with red, green, blue and alpha components. So if you
  want to have bright red pixels with four different levels of
  transparency, you must use four separate palette entries to
  accommodate them. (All four entries will have identical RGB
  components, but the alpha values will differ.) If you want all of
  your colors to have four levels of transparency, you've effectively
  reduced your total number of available colors from 256 to 64.

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