libo wrote:-colorspace gray -separate -average
When an image is grayscale, separating the channels and taking their average won't change anything. (Because if you have three numbers that are the same, taking their average makes the same number.)
The Photoshop version is taking the minimum of two images. What images?
You have an edge detector, but the IM version uses a large blur.
This Windows BAT script gives a very similar result:
Code: Select all
-colorspace gray -colorspace sRGB +write mpr:GR ^
( -clone 0 -negate -blur 0x2 ) ^
-compose ColorDodge -composite ^
-evaluate Pow 2.4 ^
( mpr:GR +level 80%%,120%% ) ^
-compose Darken -composite -colorspace sRGB ^
Tweaking the numbers may give an even closer result.