Crop a UIImage from the Center outwards? - iphone

Question

I am making a camera app which includes digital zoom. I have a slider (zoomSlider) that has a minimum value of 1 and a maximum value of 4. When the user taps the camera button, it takes a picture, and then I crop it for the zooming. I have two problems:
How do I crop the exact middle of the image? (eg. 2x zoom, Rect would be centered with dimensions of 600x800 (for iPhone 2G/3G))
When I do this, it rotates the image. I make up for it by rotating the UIImageView it's in, but this causes a portrait picture to become landscape and vice versa.
Here is my code:
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {
if ([mediaType isEqualToString:#"public.image"]){
UIImage *image = [info objectForKey:#"UIImagePickerControllerOriginalImage"];
CGRect clippedRect = CGRectMake(600, 450, image.size.width/zoomSlider.value, image.size.height/zoomSlider.value);
UIImage *cropped = [self imageByCropping:image toRect:clippedRect];
CGRect croppedImageSize = CGRectMake(0, 0, image.size.width/zoomSlider.value, image.size.height/zoomSlider.value);
[cropped drawInRect:croppedImageSize];
zoomPhoto.frame = croppedImageSize;
zoomPhoto.image = cropped;
CGAffineTransform rotateTransform = CGAffineTransformRotate(CGAffineTransformIdentity,
RADIANS(90.0));
zoomPhoto.transform = rotateTransform;
}
- (UIImage *)imageByCropping:(UIImage *)imageToCrop toRect:(CGRect)rect
{
CGImageRef imageRef = CGImageCreateWithImageInRect([imageToCrop CGImage], rect);
UIImage *cropped = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
return cropped;
}

Answer 1

CGFloat newWidth = image.size.width/zoomSlider.value;
CGFloat newHeight = image.size.height/zoomSlider.value;
CGRect clippedRect = CGRectMake((image.size.width-newWidth)/2, (image.size.height-newHeight)/2, newWidth, newHeight);
Remove this to not rotate the image:
CGAffineTransform rotateTransform = CGAffineTransformRotate(CGAffineTransformIdentity,RADIANS(90.0));
zoomPhoto.transform = rotateTransform;