Legacy ImageMagick Discussions Archive

I'm following the examples at http://www.imagemagick.org/Usage/channels/#mask_diff

I have a png photo, sluggo.png (354 pixels by 502 pixels, 72 dpi). Using sluggo.png, I created a layer in Photoshop and the drew an ellipse, feathering it 30 pixels. I inverted the ellipse, filled the inverted area (exterior of ellipse to the edges of the image) with black, and then exported the image to mask.png -- having the same dimensions and dots per inch as the image it was derived from: sluggo.png.

Goal: create an elliptically cropped image with transparency outside of the ellipse.

Here's the command I used based upon my study of the above link to the section titled "Difference Image Masking and Feathering". It is practically identical to the examples, yet I must be missing something very obvious as it did not produce the desired result: The command ran without incident.

the output.png was blank. I was expecting an oval like framing of sluggo. "Oh No!!!!"

sluggo.png

mask.png

output.png (blank white)


Using ImageMagick for Windows on XP Pro SP 3: What have I done wrong?

Problem solved.

I think the problem was in the mask I created. I tried experimenting with creating masks on the fly, as in the examples, and they worked. So, I'm guessing the way I exported the mask from photoshop, e.g. using "Save" rather than exporting and making sure the transparency is activated, makes the difference.

More than likly the mask image contained an alpha channel.

See CopyOpacity Composition
http://www.imagemagick.org/Usage/compose/#copyopacity