Crop and recreate UIImage - ios

Question

I want to crop a UIImage (not imageview), before doing pixel operations on it. Is there a reliable way to do this in ios framework?
Here are the related methods in android I am using:
http://developer.android.com/reference/android/graphics/Bitmap.html#createBitmap(android.graphics.Bitmap, int, int, int, int)
http://developer.android.com/reference/android/graphics/Bitmap.html#createBitmap(int, int, android.graphics.Bitmap.Config)

Answer 1

-(UIImage*)scaleToSize:(CGSize)size image:(UIImage*)image
{
UIGraphicsBeginImageContext(size);
// Draw the scaled image in the current context
[image drawInRect:CGRectMake(0, 0, size.width, size.height)];
// Create a new image from current context
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
// Pop the current context from the stack
UIGraphicsEndImageContext();
// Return our new scaled image
return scaledImage;
}

Answer 2

I would advise you to look at:
The CoreAnimation Apple framework to create an image context, draw in it and save this as a UIImage in RAM or save it to disk.
The CoreImage Apple framework if you want a powerful and fully customizable image manipulation solution.
A third party lib to crop and resize images: CocoaPods is a great way to quickly integrate that kind of libs… Here is a list of a some interesting image manipulation pods.

Answer 3

This worked for me:
-(UIImage *)cropCanvas:(UImage *)input x1:(int)x1 y1:(int)y1 x2:(int)x2 y2:(int)y2{
CGRect rect = CGRectMake(x1, y1, input.size.width-x2-x1, input.size.height-y2-y1);
CGImageRef imageref = CGImageCreateWithImageInRect([input CGImage], rect);
UIImage *img = [UIImage imageWithCGImage:imageref];
return img;
}