"Chase, Andrew" on wrote...
| Hi Folks,
|
| I'm working with png images that are only two colors, black and red.
| I'm using a palette and setting the black to be transparent. I start
| out with 24bit images and am trying to use the convert tool to change
| them to 8bit images. I'm using the following command:
|
| convert myFile.png PNG8:myFile.png
|
PNG8 is basically GIF color handling encoded into PNG.
I'll treat this as
convert myFile.png myFile.gif
instead.
| I've tried various options such as the -depth flag, -colors flag, and
| any other flag that looked like it would lock the bit depth. However,
| whatever I do, I always end up with an image with 2 bits per pixel
| rather than 8.
|
bit depth does not get used for GIF or PNG8. it is more for things
with variable depth like raw RGB, TXT, PPM, etc...
For PNG8 and GIF IM always uses the minimum color table (power of 2 in
size) needed to hold the number of colors in the image.
You are the first to request something other than this.
| Unfortunately, the program I'm displaying the png's in
| really doesn't like images with less that 8bits. Does anybody know how
| to force this option?
|
Then don't use PNG8 as IM uses 8bit colors in a 8bit color index.
PNG has lots of formating controls, not all implemented. Many such
controls may even be undocumented. (the -define controls)
I have tried to document them as I see them but there is not formal
source of info, other than the source code itself for this :-(
Usally things get added as users request them and Cristy has time.
| If I open the file in IrfanView and then save it in IrfanView it comes
| out with the correct 8 bit pixels, so I know it's possible.
|
Okay you always want a 256 color table.
One thing you can TRY (may not work) is to give the image a fixed -map
of 256 colors, including red and black. You could try the
colormap_332.png
image create in IM examples. (256 colors, no transparency)
http://www.imagemagick.org/Usage/quantize/#map_colormaps
Or even the builtin netscape: color map (219 colors)
Anthony Thyssen ( System Programmer ) <[EMAIL PROTECTED]>
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Anthony's Home is his Castle http://www.cit.gu.edu.au/~anthony/
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