UIImage+Contrast.m

//
//  UIImage+Contrast.m
//
//  Created by Cory Leach on 3/14/11.
//  Copyright 2011 Cory R. Leach. All rights reserved.
//

#import "UIImage+Contrast.h"


@implementation UIImage (Contrast)

- (UIImage*) imageWithContrast:(CGFloat)contrastFactor {
    
    if ( contrastFactor == 1 ) {
        return self;
    }
    
    CGImageRef imgRef = [self CGImage];
    
    size_t width = CGImageGetWidth(imgRef);
    size_t height = CGImageGetHeight(imgRef);
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    size_t bitsPerComponent = 8;
    size_t bytesPerPixel = 4;
    size_t bytesPerRow = bytesPerPixel * width;
    size_t totalBytes = bytesPerRow * height;
    
    //Allocate Image space
    uint8_t* rawData = malloc(totalBytes);
    
    //Create Bitmap of same size
    CGContextRef context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    
    //Draw our image to the context
    CGContextDrawImage(context, CGRectMake(0, 0, width, height), imgRef);
    
    //Perform Brightness Manipulation
    for ( int i = 0; i < totalBytes; i += 4 ) {
        
        uint8_t* red = rawData + i; 
        uint8_t* green = rawData + (i + 1); 
        uint8_t* blue = rawData + (i + 2); 
        
        *red = MIN(255,MAX(0, roundf(contrastFactor*(*red - 127.5f)) + 128));
        *green = MIN(255,MAX(0, roundf(contrastFactor*(*green - 127.5f)) + 128));
        *blue = MIN(255,MAX(0, roundf(contrastFactor*(*blue - 127.5f)) + 128));
    
    }
    
    //Create Image
    CGImageRef newImg = CGBitmapContextCreateImage(context);
    
    //Release Created Data Structs
    CGColorSpaceRelease(colorSpace);
    CGContextRelease(context);
    free(rawData);
    
    //Create UIImage struct around image
    UIImage* image = [UIImage imageWithCGImage:newImg];
    
    //Release our hold on the image
    CGImageRelease(newImg);
    
    //return new image!
    return image;
    
}

- (UIImage*) imageWithContrast:(CGFloat)contrastFactor brightness:(CGFloat)brightnessFactor {
    
    if ( contrastFactor == 1 && brightnessFactor == 0 ) {
        return self;
    }
    
    CGImageRef imgRef = [self CGImage];
    
    size_t width = CGImageGetWidth(imgRef);
    size_t height = CGImageGetHeight(imgRef);
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    size_t bitsPerComponent = 8;
    size_t bytesPerPixel = 4;
    size_t bytesPerRow = bytesPerPixel * width;
    size_t totalBytes = bytesPerRow * height;
    
    //Allocate Image space
    uint8_t* rawData = malloc(totalBytes);
    
    //Create Bitmap of same size
    CGContextRef context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    
    //Draw our image to the context
    CGContextDrawImage(context, CGRectMake(0, 0, width, height), imgRef);
    
    //Perform Brightness Manipulation
    for ( int i = 0; i < totalBytes; i += 4 ) {
        
        uint8_t* red = rawData + i; 
        uint8_t* green = rawData + (i + 1); 
        uint8_t* blue = rawData + (i + 2); 
        
        *red = MIN(255,MAX(0,roundf(*red + (*red * brightnessFactor))));
        *green = MIN(255,MAX(0,roundf(*green + (*green * brightnessFactor))));
        *blue = MIN(255,MAX(0,roundf(*blue + (*blue * brightnessFactor))));
        
        *red = MIN(255,MAX(0, roundf(contrastFactor*(*red - 127.5f)) + 128));
        *green = MIN(255,MAX(0, roundf(contrastFactor*(*green - 127.5f)) + 128));
        *blue = MIN(255,MAX(0, roundf(contrastFactor*(*blue - 127.5f)) + 128));
        
    }
    
    //Create Image
    CGImageRef newImg = CGBitmapContextCreateImage(context);
    
    //Release Created Data Structs
    CGColorSpaceRelease(colorSpace);
    CGContextRelease(context);
    free(rawData);
    
    //Create UIImage struct around image
    UIImage* image = [UIImage imageWithCGImage:newImg];
    
    //Release our hold on the image
    CGImageRelease(newImg);
    
    //return new image!
    return image;
    
}


@end