Question

I am googling from last few hour and get solution for crop an Image, But I am confused and wants to know what is the difference between these two?

Problem : I wants to crop a rectangle image from inside an Image, I already detected the boundary.

First :

 CGRect rect = CGRectMake(0,0,320, 460);

// Create bitmap image from original image data,
// using rectangle to specify desired crop area

CGImageRef imageRef = CGImageCreateWithImageInRect([imageView.image CGImage], rect);
UIImage *imgs = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);

Second :

CGRect rect = [backView bounds];
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();

[backView.layer renderInContext:context];

UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

Answer 1

The second method is more general, in that your backView needs not to be an UIImageView, like in the first case.

In other words, CGImageCreateWithImageInRect requires you to have a CGImage to start with:

CGImageRef imageRef = CGImageCreateWithImageInRect([imageView.image CGImage], rect);

on the other hand with renderInContext you can render any view into an image:

[backView.layer renderInContext:context];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();