Category for trimming transparent pixels of an UIImage object.
Add the UIImage+Trim files to your project. Include UIImage+Trim.h in the files where you want to trim your images.
Trimming is pretty straightforward:
[yourImage imageByTrimmingTransparentPixels];
Optionally, you may want to consider any non-opaque pixels as being transparent (for instance, cropping out a light drop shadow). This can be achieved by using the alternate method:
[yourImage imageByTrimmingTransparentPixelsRequiringFullOpacity:YES];
Additionally, if you merely desire to know the UIEdgeInsets of the transparency around the image, you may want to use the following:
[yourImage transparencyInsetsRequiringFullOpacity:YES];
This call works based on the same principles as the "advanced" trim method, with the boolean dictating whether non-opaque pixels should be considered transparent.
This fork adds support for trimming white area around image with given tolerance
[yourImage imageByTrimmingWhitePixelsWithOpacity:VALUE];
where 0 - cut only white, 255 - remove everything