Re: opacity

On Wed, 26 May 2004, Patrick Welche wrote:

> This is probably a FAQ, but I haven't found a solution. Essentially I
> want to do
>
>  gm convert -mask mask.eps skill.eps out.png
>
> but try as I may, out.png is not transparent. I tried converting the eps to
> png first, so mask.png is an anti-aliased black ellipse on a white background.
> I then want to say, "make the opacity chanel of out.png the same as the
> (any of R, G or B) channel of mask.png". I can see how you copy say Red to
> Red, or Opacity to Opacity, but not from one to the other. (I have a feeling
> that -mask should do exactly what I want, but it doesn't seem to..)

My understanding is that the mask image provided using -mask is used 
to protect pixels (mask) from being modified by subsequent operations. 
I don't believe that EPS files support transparency so transparency 
would have to be added.

I believe that you can use the 'gm composite' command with the 
'-compose CopyOpacity' option to add an opacity channel.  I am not 
aware of a way to do it using a single command using GraphicsMagick.

Bob
======================================
Bob Friesenhahn
[email protected]
http://www.simplesystems.org/users/bfriesen


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