Legacy ImageMagick Discussions Archive

And, of course, you can multiply instead of divide: convert logo.png -alpha on -channel A -evaluate multiply 0.25 +channel result.png This is the solution! Works perfect, and instead of Divide you use Multiply! Clever, thank you! That allow me to use 0-1 values for my level of transparency. Thanks ...

Post your original image. You need to turn on all the channels after selecting to process only the alpha channel. Try convert image -alpha on -channel a -evaluate set 30% +channel result or convert image -alpha on -background black -alpha background -channel a -evaluate set 30% +channel result This ...

Thanks for the help guys!
I will try that out.

Best,

Hi all, I need to change the opacity or alpha of my image based on a float variable from 0.0 to 1.0. 0 = transparent, 0.5 = half transparent and 1 = opaque. This is a classic function that you find in many softs and also Imagic for PHP. See: http://www.php.net/manual/en/imagick.setimageopacity.php I ...