Legacy ImageMagick Discussions Archive

from app/operations/gimplevelsconfig.c gimp_levels_config_adjust_by_colors (GimpLevelsConfig *config, GimpHistogramChannel channel, const GimpRGB *black, const GimpRGB *gray, const GimpRGB *white) { [...] if (gray) { gdouble input; gdouble range; gdouble inten; gdouble out_light; gdouble lightness ...

ok maybe I wasn't clear enough. in gimp the user clicks on "pick grey point" from "levels" dialog and picks a color. gimp magically transforms that color in some gamma values for each channel and applies them, resulting a new image. now what I want is to simulate this behavior with imagemagick. so ...

i'm getting close. so for value (r,g,b) picked by user I'll calculate the gamma for each channel: static double sRGB_to_linear(double x) { if (x < 0.04045) return x/12.92; return Math.pow((x+0.055)/1.055, 2.4); } double R_linear = sRGB_to_linear(r/255.0); double G_linear = sRGB_to_linear(g/255.0 ...

thank you all of you for replies!

@fmw42: nice tip the one with hald image. but I'm not sure I understand first part. so I have an image and a picked rgb value.
how this rgb values fits in the convert example. AFAIK gamma value is between 0.1 ant 10. do I miss something ?

hi, I trying to simulate "pick grey point" from gimp "levels" dialog with convert. for "black point" and "white point" I use: $ convert -level-colors 'rgb(0,0,0),rgb($RED,$GREEN,$BLUE)' in.jpg out.jpg and $ convert -level-colors 'rgb($RED,$GREEN,$BLUE),rgb(255,255,255)' in.jpg out.jpg any idea what ...