Use image as overlay mask for opacity for another image via imageMagick


Wed Jun 09 2021 08:17:27 GMT+0000 (Coordinated Universal Time)

Saved by @dphillips #image #convert #gradient #clipping #mask #transparency #typo3 #imagemagick

# You can use imageMagick to create a gradient image on the fly, but with all the weird possibilities I didn't quite get the hang of it (yet). Anyway, a default 50:50 gradient can be created via "convert -size 100x100 gradient:black-white target.png". To shift the center, you can chain multiple gradients and use the ""-append" flag
❯ convert -size 1000x600 gradient:black-black -size 1000x400 gradient:black-none -append gradient.png

# To use the gradient as a mask on your image, they should be the same size. You can easily resize the image. But keep in mind that imageMagixk respects the proportions and resizes X and Y according to the smaller value
❯ convert gradient.png -resize 1200x800 gradient_resized.png

# Here is how to combine the two, so that you're left with a new image with the mask applied
❯ convert content.jpg gradient_resized.png -alpha on -compose CopyOpacity -composite result.png

Only tried with black for mask color. But since it uses the alpha channel of the mask image the color should be irelevant.

terminal help output, try and error and brain stuff