Changing image hue iOS

Question

I want to change hue of an image using slider. what I did is:

float slideValue =  sldHueChange.value;
beginImage= [CIImage imageWithCGImage:imgBorder.image.CGImage];
context = [CIContext contextWithOptions:[NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES] forKey:kCIContextUseSoftwareRenderer]];
filter= [CIFilter filterWithName:@"CIHueAdjust"];
[filter setValue:beginImage forKey:kCIInputImageKey];
[filter setValue:[NSNumber numberWithFloat:slideValue] forKey:@"inputAngle" ];
CIImage *outputImage = [filter outputImage];
CGImageRef cgimg =[context createCGImage:outputImage fromRect:[outputImage extent]];
UIImage *newImg = [UIImage imageWithCGImage:cgimg];
[imgBorder setImage:newImg];
CGImageRelease(cgimg);

Its working. But it is not smooth. I want a to change hue of image very smoothly. If you have idea to make a smooth hue changer please share it. I really need it. Thanks in advance.

Answer 1

Now what I'm doing is:

CGRect rect = CGRectMake(0, 0, selectedBorderForChangingHue.size.width, selectedBorderForChangingHue.size.height);
UIGraphicsBeginImageContext(rect.size);
CGContextRef context1 = UIGraphicsGetCurrentContext();
CGContextClipToMask(context1, rect, selectedBorderForChangingHue.CGImage);
CGContextSetFillColorWithColor(context1, [[UIColor colorWithHue:sldHueChange.value/255.0f saturation:1.0f brightness:1.0f alpha:1.0f] CGColor]);
CGContextFillRect(context1, rect);
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImage *flippedImage = [UIImage imageWithCGImage:img.CGImage scale:1.0 orientation: UIImageOrientationDownMirrored];
imgBorder.image = flippedImage;

and it is working fine for me. and it is very smooth.

Answer 2

I would suggest you to use the amazing GPUImage from Brad, it has a lot of filters, or you can try to use the GPU render for CIContext, changing the boolean to NO in the options dictionary for the CIContext creation.