I would compose the images using the Multiply operator. The command
convert src.png overlay.png -compose Multiply -geometry 948x630 -composite out.png
produces:
Question
Given a RGB image :
Given a grey scale, opacity 0% to opacity 100% black image:
How to add the alpha shadows upon the RGB image using a shell command ? (preferemce for ImageMagick Convert)
Solution
I would compose the images using the Multiply operator. The command
convert src.png overlay.png -compose Multiply -geometry 948x630 -composite out.png
produces:
OTHER TIPS
I believe the example "Using Masks with Images" covers this. Simply disable the alpha channel, and copy over the second image as opacity composite. Add -negate
option to invert the 0% ~ 100% opacity -- if needed.
convert map_image.png elevation_mask.png \
-alpha Off -compose CopyOpacity -composite \
out.png