[magick-users] swap black for white

[Anthony Thyssen]

On Thu, 30 Apr 2009 20:23:47 -0600
Bob Meetin <bobm at dottedi.biz> wrote:

| I have a series of .gif images with transparency which when uploaded to 
| a shopping cart, the utility converts the transparency to black.
| 
| How can I use convert, what syntax, to swap the black for either 
| transparency or white?  I can set up a PHP script to run through the list.
| 
| -Bob
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Just use    -background white -alpha shape
to make black transparent

and     -negate -background black -alpha shape
to make white transparent

This will make grays semi-transparent, and thus ensure the image
remains properly anti-aliased for non GIF image formats.

See http://www.imagemagick.org/Usage/basics/#alpha_shape


for other colors use  +level-colors
   http://www.imagemagick.org/Usage/color/#level-colors

  Anthony Thyssen ( System Programmer )    <A.Thyssen at griffith.edu.au>
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    Experience is what you get when you were expecting something else.
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     Anthony's Home is his Castle     http://www.cit.gu.edu.au/~anthony/