On Sun, 17 May 2009 16:41:50 +0200
"Jonnie Walker" <[email protected]> wrote:
| Hi ImageMagick users,
|
| I was wondering on how to specify a transparent color for a PNG image that
uses a palette. The options "transparent" and "transparent-color" do not work.
They either create an alpha mask or nothing happens at all.
|
| In the basic usage description the following is documented:
| "Transparency in such images are usually handled either by specifying a
specific color as representing transparency (set using the "-transparent-color"
meta-data setting) as in GIF format, or using a special profile for a specific
number of colors in the color table in a PNG8 image. However only a single
color transparency is implemented in IM bit image formats at this time."
| So I assume that it is possible to specify at least one transparency color.
|
| Thank you in advance for your help.
|
I would have thought for a PNG8 image the transparent color with be
specified with "-transparent-color"
however that setting does not make that color transparent, It only
specifies the color that will be added to the color index table for
transparency. that is any transparency will be given the transparent
color index, which is assigned the -transparent-color" setting.
that is you need to do BOTH. make a color transparent, and tell
Im what color the transparent index should have.
At least that is how it works for GIF, and PNG8 is supposed to be
similar. If this has changed, no one has told me that it is different.
Hmmmm
convert -size 100x100 gradient: -fuzz 30% -transparent gray50 \
-transparent-color red png8:test.png
convert: Invalid background palette index `test.png' @
png.c/PNGWarningHandler/1429.
hmmm looks like the PNG coder is broken. Reporting in the bugs forum.
Anthony Thyssen ( System Programmer ) <[email protected]>
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