How to Crop an Image (UIImage) On iOS
June 3, 2010
In October of 2012 I wrote another example to crop an image, which requires a lot less code.
This post shows an example of one way to crop an image. Let’s begin by looking at a screenshot of the original and cropped image on the iPhone simulator:
As you can see, I am cropping a rectangle from the middle of the image on the top left. The code below shows how to accomplished this:
// Create the image from a png file UIImage *image = [UIImage imageNamed:@"prgBinary.jpg"]; UIImageView *imageView = [[UIImageView alloc] initWithImage:image]; // Get size of current image CGSize size = [image size]; // Frame location in view to show original image [imageView setFrame:CGRectMake(0, 0, size.width, size.height)]; [[self view] addSubview:imageView]; [imageView release]; // Create rectangle that represents a cropped image // from the middle of the existing image CGRect rect = CGRectMake(size.width / 4, size.height / 4 , (size.width / 2), (size.height / 2)); // Create bitmap image from original image data, // using rectangle to specify desired crop area CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], rect); UIImage *img = [UIImage imageWithCGImage:imageRef]; CGImageRelease(imageRef); // Create and show the new image from bitmap data imageView = [[UIImageView alloc] initWithImage:img]; [imageView setFrame:CGRectMake(0, 200, (size.width / 2), (size.height / 2))]; [[self view] addSubview:imageView]; [imageView release];
All the heavy lifting is done by the method CGImageCreateWithImageInRect, which creates a new bitmap image using existing image data and a rectangle that is a subregion of that same image. Once cropped, I create a new UIImageView and add it as a subview of the current view.