Return a subimage from a UIImage

Question

I want to grab a subimage from a UIImage. I\'ve looked around for a similar question, to no avail.

I know the range of pixels I want to grab - how can I return th

Answer 1

Updated @donkim answer for swift 3:

    let fromRect=CGRect(x:0,y:0,width:320,height:480)
    let drawImage = image.cgImage!.cropping(to: fromRect)
    let bimage = UIImage(cgImage: drawImage!)

Answer 2

In Swift 4, taking into account screen scale (otherwise your new image will be too large):

    let img = UIImage(named: "existingImage")!
    let scale = UIScreen.main.scale
    let dy: CGFloat = 6 * scale // say you want 6pt from bottom
    let area = CGRect(x: 0, y: img.size.height * scale - dy, width: img.size.width * scale, height: dy)
    let crop = img.cgImage!.cropping(to: area)!
    let subImage = UIImage(cgImage: crop, scale: scale, orientation:.up)

Answer 3

This should help: http://iphonedevelopment.blogspot.com/2010/11/drawing-part-of-uiimage.html

This code snippet is creating a category of UIImage but the code should be easily modified to work without it being a category.

A shorter way of doing the same thing is the following:

CGRect fromRect = CGRectMake(0, 0, 320, 480); // or whatever rectangle

CGImageRef drawImage = CGImageCreateWithImageInRect(image.CGImage, fromRect);
UIImage *newImage = [UIImage imageWithCGImage:drawImage];
CGImageRelease(drawImage);

Hope this helps!