UIImage Category to help with IR photo processing tasks

UIImage+IRHelpers

//
//  UIImage+IRHelpers.m
//  RedStudio
//
//  Created by Brian Cook on 6/4/12.
//  Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//

#import "UIImage+IRHelpers.h"
#import <Accelerate/Accelerate.h>

CGContextRef CreateARGBBitmapContext(const size_t width, 
                                     const size_t height, 
                                     const size_t bytesPerRow) {
    
	CGContextRef bmContext = CGBitmapContextCreate(NULL, 
                                                   width, 
                                                   height, 
                                                   8, 
                                                   bytesPerRow, 
                                                   CGColorSpaceCreateDeviceRGB(), 
                                                   kCGBitmapByteOrderDefault | 
                                                   kCGImageAlphaPremultipliedFirst);
    
	return bmContext;
}

@implementation UIImage (IRHelpers)

- (UIImage *)swapRedAndBlueChannels {
    CGImageRef image = self.CGImage;
    size_t width = CGImageGetWidth(image);
    size_t height = CGImageGetHeight(image);
    size_t bytesPerRow = width * 4;
    
    CGContextRef bmContext = CreateARGBBitmapContext(width, height, bytesPerRow);
    CGContextDrawImage(bmContext, CGRectMake(0.0f, 0.0f, width, height), image);
    
    UInt8* imageData = CGBitmapContextGetData(bmContext);
    
    const size_t n = sizeof(unsigned char) * width * height * 4;
    void *outBuffer = malloc(n);
    vImage_Buffer src = {imageData, height, width, bytesPerRow};
    vImage_Buffer dest = {outBuffer, height, width, bytesPerRow};
    
    //ARGB to ABGR
    const uint8_t map[4] = {0, 3, 2, 1};
    vImagePermuteChannels_ARGB8888(&src, &dest, map, kvImageNoFlags);
    
    memcpy(imageData, outBuffer, n);
    free(outBuffer);
    
    CGImageRef result = CGBitmapContextCreateImage(bmContext);
    UIImage *outImage = [UIImage imageWithCGImage:result];
    
    CGContextRelease(bmContext);
    CGImageRelease(result);
    
    return outImage;
}

- (UIImage *)equalizeImage {
    CGImageRef image = self.CGImage;
    size_t width = CGImageGetWidth(image);
    size_t height = CGImageGetHeight(image);
    size_t bytesPerRow = width * 4;
    
    CGContextRef bmContext = CreateARGBBitmapContext(width, height, bytesPerRow);
    CGContextDrawImage(bmContext, CGRectMake(0.0f, 0.0f, width, height), image);
    
    UInt8* imageData = CGBitmapContextGetData(bmContext);
    
    const size_t n = sizeof(UInt8) * width * height * 4;
    void *outBuffer = malloc(n);
    vImage_Buffer src = {imageData, height, width, bytesPerRow};
    vImage_Buffer dest = {outBuffer, height, width, bytesPerRow};
    vImage_Error err = vImageEqualization_ARGB8888(&src, &dest, kvImageCopyInPlace);
    
    if (err == kvImageNoError) {
        memcpy(imageData, outBuffer, n);
    }
    
    free(outBuffer);
    
    CGImageRef result = CGBitmapContextCreateImage(bmContext);
    UIImage *outImage = [UIImage imageWithCGImage:result];
    
    CGContextRelease(bmContext);
    CGImageRelease(result);
    
    return outImage;
}

- (UIImage *)stretchContrast {
    CGImageRef image = self.CGImage;
    size_t width = CGImageGetWidth(image);
    size_t height = CGImageGetHeight(image);
    size_t bytesPerRow = width * 4;
    
    CGContextRef bmContext = CreateARGBBitmapContext(width, height, bytesPerRow);
    CGContextDrawImage(bmContext, CGRectMake(0.0f, 0.0f, width, height), image);
    
    UInt8* imageData = CGBitmapContextGetData(bmContext);
    
    const size_t n = sizeof(UInt8) * width * height * 4;
    void *outBuffer = malloc(n);
    vImage_Buffer src = {imageData, height, width, bytesPerRow};
    vImage_Buffer dest = {outBuffer, height, width, bytesPerRow};
    vImage_Error err = vImageContrastStretch_ARGB8888(&src, &dest, kvImageCopyInPlace);
        
    if (err == kvImageNoError) {
        memcpy(imageData, outBuffer, n);
    }
        
    free(outBuffer);
    
    CGImageRef result = CGBitmapContextCreateImage(bmContext);
    UIImage *outImage = [UIImage imageWithCGImage:result];
    
    CGContextRelease(bmContext);
    CGImageRelease(result);
    
    return outImage;
}


@end