Crop with PNG on PNG [resolved]

[weblife]

Anyone have a suggestion for how I can alter the following command to crop one PNG with another PNG?

Code: Select all

convert artwork.png alpha.png -gravity Center -alpha Off -compose copy_opacity -composite out.png

Currently the issue I am seeing is on my existing PNG image a black block appears where another PNG was placed to a transparent canvas.

+ =

My Version: ImageMagick 6.9.1-10 Q16 x86_64 2015-07-26
Platform: Mac OSX El Capitan 10.11.6

[fmw42]

What is your IM version and platform? Please always provide that.

[weblife]

Placed platform in above also. Sorry.

[fmw42]

try

Code: Select all

convert \( artwork.png -alpha extract \)  alpha.png -gravity Center -alpha Off -compose copy_opacity -composite out.png

Is this what you want.

Your problem is that your artwork image has the detail in the alpha channel and not the base image. So you need to extract the detail from the alpha channel of artwork and use that.

[fmw42]

Or perhaps you want this with the polarity switched in the artwork texture.

Code: Select all

convert \( artwork.png -alpha extract -negate \)  alpha.png -gravity Center -alpha Off -compose copy_opacity -composite out2.png

[weblife]

Thank you Fred. Much closer. The second output is closer to what I am looking to do "out2.png". I was able to achieve that with flatten :

Code: Select all

convert artwork.png -flatten alpha.png -gravity Center -alpha Off -compose copy_opacity -composite png:out.png 

I want to keep the white area transparent also. Need to see if I alter my alpha.png white to transparent will achieve this.

[weblife]

I should clarify. I want to keep the transparent area transparent from "artwork.png".

[fmw42]

You will need to separate the alpha channels and then multiply them (possibly with one negated), then use the combined alpha channel and put that back on the image.

Note that transparent means the alpha channel will be black in those areas, not white.

[weblife]

Okay, here is what I did to achieve:

Code: Select all

convert \( artwork.png -gravity center -extent 2000x2000 -fuzz 9% -transparent white \) \
alpha.png -gravity center -alpha On -compose copy_opacity \
-composite -fuzz 9% -transparent white altered.png