Эта категория сделает всю работу за вас -
UIImage + Additions.h -
@interface UIImage (UIImageAdditions)
- (UIImage*)scaleToSize:(CGSize)size;
@end
UIImage + Additions.m -
@implementation UIImage (UIImageAdditions)
- (UIImage*)scaleToSize:(CGSize)size {
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextTranslateCTM(context, 0.0, size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, size.width, size.height), self.CGImage);
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return scaledImage;
}
@end