NSData *imgData1 = UIImageJPEGRepresentation(newImage, 1.0f);
NSLog(@"1.0 size: %d", imgData1.length);
NSData *imgData2 = UIImageJPEGRepresentation(newImage, 0.7f);
NSLog(@"0.7 size: %d", imgData2.length);
NSData *imgData3 = UIImageJPEGRepresentation(newImage, 0.4f);
NSLog(@"0.4 size: %d", imgData3.length);
NSData *imgData4 = UIImageJPEGRepresentation(newImage, 0.0f);
NSLog(@"0.0 size: %d", imgData4.length);
Использование
UIImage *reducedImage = [UIImage imageWithData: imgData2];