[magick-users] Changing the Alpha color in a PNG

[Fred Weinhaus]

Make a post with the commands you are using to modify your image and 
tell us what you are trying to accomplish. It seems that you are 
changing white to black somewhere where there is transparency.  Is 
that intended?  Also post a link to your input and output images so 
we can see what is going on.


>Hi,
>     I am using convert to process images.  The inputs and output are
>PNGs which has some completely transparent pixels.  identify -verbose
>on an input file has a line like this:
>
>Alpha: (255,255,255,255)        #FFFFFFFF
>
>Identify -verbose has a line on the output image like this:
>
>Alpha: (  0,  0,  0,255)        #000000FF
>
>The full output from both commands is at the end of this message.
>
>When a user views the output image in a program known to not
>completely support PNG, the pixels of the output image that should be
>transparent are black.  My guess is that this program is tossing out
>the alpha channel entirely, and the alpha color #000000FF becomes
>#000000, or black.  I would like to make the alpha color #FFFFFFFF, so
>that transparent pixels become white when transparency is dropped.
>Can I chose the alpha color in ImageMagick?  If so, how?
>
>Sam