[magick-users] Transparency problem when converting png from 24-bit to 8-bit

[Fred Weinhaus]

Not sure at this point what your issue is besides the PNG8: not 
working correctly?  Your first step is SVG to PNG, I presume. So what 
is the question, once you have it as PNG?

Your image had an alpha channel that was the mask. The image was 
Class: DirectClass and Type: GrayscaleMatte. The image had a white 
box on a black background with black edges and black "Jobs" written 
on it. The alpha mask was white for the box interior and black 
outside (except not pure b/w but had some antialiasing of the edges). 
Thus where (near) black you got transparency and where (near) white 
you got your box image.

What is that you want to do? Change the background around the box 
from transparent to some other color? Or is change the image to 
Class: PseudoClass and  Type: GrayscaleMatte to make its filesize 
smaller? The latter can be done as simply:

convert jobs_original.png GIF:- | convert - jobs_original_gif_png8.png

without the PNG8: prefix


Don't know why PNG8: is not working correctly as in:

convert jobs_original.png PNG8:jobs_original_png8.png


but you should report it to the bugs forum at
http://www.imagemagick.org/discourse-server/viewforum.php?f=3

I would also suggest you use the User's forum at
http://www.imagemagick.org/discourse-server/viewforum.php?f=1

in stead of the Magick Users List

as it is easier to reply and you will likely get more viewers and responders.


Fred


>However, I'm still intrigued as to what the best way of proceeding
>woulf be if I didn't have the luxury of rerunning that first step. I
>tried making a mask and applying that but I still ended up with the
>black disappearing.