Trimming colour issues

[runmad]

Thanks for this library. However, I seem to have issues using the trimming utility. I assign a UIColor with RGB colour space, but it doesn't actually trim the image.

Here's an example of an image I am trying to trim:

I'm wanting to trim the black borders on the top and bottom, so I set the UIColor to [UIColor colorWithRed:0 green:0 blue:0 alpha:1]] but I am returned the exact same image, nothing is being trimmed.

[cameronehrlich]

I believe the problem is that starting right here the code assumes that black and white are represented with 4 components like all the other colors in the RGBA colorspace. After debugging and hunting around I figured out that black and white are represented by a seemingly undocumented color space kCGColorSpaceDeviceGray which causes this to evaluate to true: CGColorGetNumberOfComponents([UIColor black].CGColor) == 2

Because of this, line 40 returns NULL. Additionally, the assumptions made in line 48 will not produce the expected outcome when trying to crop out black or white borders.

I hacked together a UIImage category today that I believe handles this issue correctly. I intend to expand upon it to be more full featured for use in an app I am working on, but feel free to borrow and/or contribute back!

https://github.com/cameronehrlich/ImageTrim/blob/master/ImageTrim/UIImage%2BImageTrim.m

Possible things I would like to add are:

• Auto-Detection of border color
• Better color tolerance logic
• The ability to set a minimum width or height that can be cropped to so as to avoid weird image slivers.
• The option to choose which sides you'll apply the trimming to.