How i apply a mask to a grayscale image ?

[nars]

Hi,

I want apply a mask to an image. (image and mask have the same dimensions)

input.png (grayscale)
mask.png

I used the next code:

convert input.png mask.png -alpha off -compare CopyOpacity -composite out.png

The mask was applied correctly, but the out.png lost the grayscale (obviously), i think..

Suggestions for applying the mask and not lose the grayscale ?

thanks

[snibgo]

Use "-compose" instead of "-compare":

Code: Select all

convert input.png mask.png -alpha off -compose CopyOpacity -composite out.png

If that doesn't help, upload inputs and output to somewhere like dropbox.com and paste the URLs here.

[nars]

The same :/

Mask image:


Input image:

[snibgo]

Code: Select all

convert 2z4er1s.png 14j5cmw.png -alpha off -compose CopyOpacity -composite outMasked.png

This is the result:

It looks fine to me. What result do you get? What is wrong with it?

[nars]

yes, it looks fine.. Sorry, bad example :/

With the next images, you can see the differences.

input:


mask:


Thanks

[snibgo]

Again, the result looks fine to me. What is wrong with it?

Code: Select all

convert elcqxy.jpg.png 2ueigev.jpg.png -alpha off -compose CopyOpacity -composite outMasked2.png

[nars]

My result:



My code:

Code: Select all

convert input2.png mask2.png -alpha off -compose CopyOpacity -composite outMasked_2.png

Why is different?

Thanks

[fmw42]

What version of IM and platform are you using?

Nothing is wrong with it. Your two examples are on different color backgrounds, which show through in the transparent areas.

[nars]

Version: ImageMagick 6.7.7-10 2014-03-06

Platform: Linux - Ubuntu

Thanks

[snibgo]

Your result is darker than mine, because your old version of ImageMagick 6.7.7-10 was confused between linear and non-linear grayscale. I suggest you upgrade to a recent version.

[nars]

Yes, I update ImageMagick to a recent version and solved my problem.

Thanks