issue with cropImage method on image in UIScrollView yields wrong image - ios

Question

I am using the following crop method to crop a uiimage that's sitting in a UIImageView which is then sitting in a UIScrollView.
-(UIImage *)cropImage:(UIImage *)image
{
float scale = 1.0f/_scrollView.zoomScale;
NSLog(#"Oh and heres that zoomScale: %f", _scrollView.zoomScale);
CGRect visibleRect;
visibleRect.origin.x = _scrollView.contentOffset.x * scale;
visibleRect.origin.y = _scrollView.contentOffset.y * scale;
visibleRect.size.width = _scrollView.bounds.size.width * scale;
visibleRect.size.height = _scrollView.bounds.size.height * scale;
NSLog(#"Oh and here's that CGRect: %f", visibleRect.origin.x);
NSLog(#"Oh and here's that CGRect: %f", visibleRect.origin.y);
NSLog(#"Oh and here's that CGRect: %f", visibleRect.size.width);
NSLog(#"Oh and here's that CGRect: %f", visibleRect.size.height);
CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], visibleRect);
UIImage *croppedImage = [[UIImage alloc] initWithCGImage:imageRef];
CGImageRelease(imageRef);
return croppedImage;
}
I need the image to be cropped to a CGSize of (321,115). Upon cropping the image and seeing the print results, I can see that visibleRect is (0,0,321,115) - what it is supposed to be, the croppedImage UIImage then has width:321 and height:115. for some reason however the image appears to be zoomed in entirely too far (the method cropped a smaller portion of the original image to a size of 321x115).
Why is this method not correctly cropping my image?
-As a side note: When I call this method, I am calling like so _croppedImage = [self cropImage:_imageView.image]; which sets a UIImage property of a custom UIView class to the cropped image.

Answer 1

Please try this function. It may help you.
Parameters:
UIImage
CGSize (321,115) or any size
// crop image - image will crop from full image
- (UIImage *)cropImageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {
double ratio;
double delta;
CGPoint offset;
//make a new square size, that is the resized imaged width
CGSize sz = CGSizeMake(newSize.width, newSize.width);
//figure out if the picture is landscape or portrait, then
//calculate scale factor and offset
if (image.size.width > image.size.height) {
ratio = newSize.width / image.size.width;
delta = (ratio*image.size.width - ratio*image.size.height);
offset = CGPointMake(delta/2, 0);
}
else {
ratio = newSize.width / image.size.height;
delta = (ratio*image.size.height - ratio*image.size.width);
offset = CGPointMake(0, delta/2);
}
//make the final clipping rect based on the calculated values
CGRect clipRect = CGRectMake(-offset.x,
-offset.y,
(ratio * image.size.width) + delta,
(ratio * image.size.height) + delta);
//start a new context, with scale factor 0.0 so retina displays get
//high quality image
if ([[UIScreen mainScreen] respondsToSelector:#selector(scale)]) {
UIGraphicsBeginImageContextWithOptions(sz, YES, 0.0);
} else {
UIGraphicsBeginImageContext(sz);
}
UIRectClip(clipRect);
[image drawInRect:clipRect];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
To crop only selected portion of image
Please check this link