Legacy ImageMagick Discussions Archive

I want create a blue doughnut on transparent background. So far I have a circle on trans[arenty background with a white middle:

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convert -size 1001x1001 xc:white -alpha transparent transparent.png
convert transparent.png -fill "#2244aa" -stroke "#2244aa" -draw "circle 500,500 1,500" circle.png
convert circle.png -fill "white" -stroke "white" -draw "circle 500,500 400,500" circle.png
convert circle.png -resize 19x19 circle.png

How can I make the middle transparent instead of white? I tried -alpha transparent, but this gives me a completely white result:

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convert circle.png -draw "circle 500,500 400,500"  -alpha transparent circle.png

I'm looking for some way to "draw" with transparency as the color.

Thanks for all pointers in advance!

I would draw a grayscale image, then copy-opacity that to form the alpha channel:

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convert -size 1001x1001 xc:#2244aa ^
  ( +clone -fill Black -colorize 100 ^
    -fill White -draw "circle 500,500,1,500" ^
    -fill Black -draw "circle 500,500,400,500" ^
  ) ^
  -alpha off ^
  -compose CopyOpacity -composite ^
  out.png

(Windows BAT syntax. Adjust for bash.)

Thanks snibgo. Will try it out.

From the script I understand that you create the doughnut in b/w and then use the black parts as a "stamp" to put on a empty (=transparent) background. Very clever!

A Number of ways... Here are two...

Using Masks with Images
http://www.imagemagick.org/Usage/masking/#masks

Composing using Duff-Porter methods, Specifically with Dst-Out
http://www.imagemagick.org/Usage/compose/#dstout

But essentially you want to manipulate the images alpha channel, either directly as in the first, or using alpha composition, as in the second.

Anthony

Legacy ImageMagick Discussions Archive

How to draw with tranparent color / how draw erasures?

How to draw with tranparent color / how draw erasures?

Re: How to draw with tranparent color / how draw erasures?

Re: How to draw with tranparent color / how draw erasures?

Re: How to draw with tranparent color / how draw erasures?