Cropping dependant on image contents

matthewsnape has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Cropping dependant on image contents by merlyn (Sage) on May 10, 2005 at 23:07 UTC
I'm sure there's some PerlMagic Image::Magick do-dad that will do that. The trick is just getting through the mostly opaque documentation. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply]
Re^2: Cropping dependant on image contents by davidrw (Prior) on May 11, 2005 at 02:14 UTC
I've used Image::Magick's Trim() method with success before. (though I definitely agree that the PerlMagick docs are not the best). My only caveat in using the Trim() method is that my use was when i started with a blank canvas and put stuff in the middle somewhere and wanted it auto-cropped down. In your (OP) case, you may need to tell it what to consider as the background color before calling Trim().	[reply]
Re: Cropping dependant on image contents by rduke15 (Beadle) on May 10, 2005 at 23:43 UTC
I don't see how you could avoid walking through the pixels, but of course, you don't have to examine them all. For each of the 4 sides, you only walk the lines inward from the edge, until you bump into the first "color-to-keep" pixel, then you go to the next side.	[reply]
Re: Cropping dependant on image contents by Joost (Canon) on May 10, 2005 at 23:12 UTC
There's possibly a better algorithm than walking every pixel, but if raw speed is of importance, a good graphics library in C is probably best. The only "library" that I can think of that has this functionality built-in and has good perl bindings is the "autocrop" function in Gimp. "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply]
Re: Cropping dependant on image contents by davidrw (Prior) on May 11, 2005 at 13:40 UTC
Probably best way is one of the above (Image::Magick or gimp), but as mentioned by rduke15, you have to go through pixels, but not all of them. I actualy did this recently, but in a C# program. The code is below if it helps at all as pseudocode. It takes a couple shortcuts in the loop bounds to try to check the minimum number of pixels. Read more... (3 kB)	[reply] [d/l]