convertUIImageToBitmapRGBA8

/*
 * The MIT License
 *
 * Copyright (c) 2011 Paul Solt, PaulSolt@gmail.com
 *
 * https://github.com/PaulSolt/UIImage-Conversion/blob/master/MITLicense.txt
 *
 */

#import <Foundation/Foundation.h>


@interface ImageHelper : NSObject {
    
}

/** Converts a UIImage to RGBA8 bitmap.
 @param image - a UIImage to be converted
 @return a RGBA8 bitmap, or NULL if any memory allocation issues. Cleanup memory with free() when done.
 */
+ (unsigned char *) convertUIImageToBitmapRGBA8:(UIImage *)image;

/** A helper routine used to convert a RGBA8 to UIImage
 @return a new context that is owned by the caller
 */
+ (CGContextRef) newBitmapRGBA8ContextFromImage:(CGImageRef)image;


/** Converts a RGBA8 bitmap to a UIImage. 
 @param buffer - the RGBA8 unsigned char * bitmap
 @param width - the number of pixels wide
 @param height - the number of pixels tall
 @return a UIImage that is autoreleased or nil if memory allocation issues
 */
+ (UIImage *) convertBitmapRGBA8ToUIImage:(unsigned char *)buffer 
    withWidth:(int)width
    withHeight:(int)height;

@end

/*
 * The MIT License
 *
 * Copyright (c) 2011 Paul Solt, PaulSolt@gmail.com
 *
 * https://github.com/PaulSolt/UIImage-Conversion/blob/master/MITLicense.txt
 *
 */

#import "ImageHelper.h"


@implementation ImageHelper


+ (unsigned char *) convertUIImageToBitmapRGBA8:(UIImage *) image {
    
    CGImageRef imageRef = image.CGImage;
    
    // Create a bitmap context to draw the uiimage into
    CGContextRef context = [self newBitmapRGBA8ContextFromImage:imageRef];
    
    if(!context) {
        return NULL;
    }
    
    size_t width = CGImageGetWidth(imageRef);
    size_t height = CGImageGetHeight(imageRef);
    
    CGRect rect = CGRectMake(0, 0, width, height);
    
    // Draw image into the context to get the raw image data
    CGContextDrawImage(context, rect, imageRef);
    
    // Get a pointer to the data    
    unsigned char *bitmapData = (unsigned char *)CGBitmapContextGetData(context);
    
    // Copy the data and release the memory (return memory allocated with new)
    size_t bytesPerRow = CGBitmapContextGetBytesPerRow(context);
    size_t bufferLength = bytesPerRow * height;
    
    unsigned char *newBitmap = NULL;
    
    if(bitmapData) {
        newBitmap = (unsigned char *)malloc(sizeof(unsigned char) * bytesPerRow * height);
        
        if(newBitmap) {    // Copy the data
            for(int i = 0; i < bufferLength; ++i) {
                newBitmap[i] = bitmapData[i];
            }
        }
        
        free(bitmapData);
        
    } else {
        NSLog(@"Error getting bitmap pixel data\n");
    }
    
    CGContextRelease(context);
    
    return newBitmap;    
}

+ (CGContextRef) newBitmapRGBA8ContextFromImage:(CGImageRef) image {
    CGContextRef context = NULL;
    CGColorSpaceRef colorSpace;
    uint32_t *bitmapData;
    
    size_t bitsPerPixel = 32;
    size_t bitsPerComponent = 8;
    size_t bytesPerPixel = bitsPerPixel / bitsPerComponent;
    
    size_t width = CGImageGetWidth(image);
    size_t height = CGImageGetHeight(image);
    
    size_t bytesPerRow = width * bytesPerPixel;
    size_t bufferLength = bytesPerRow * height;
    
    colorSpace = CGColorSpaceCreateDeviceRGB();
    
    if(!colorSpace) {
        NSLog(@"Error allocating color space RGB\n");
        return NULL;
    }
    
    // Allocate memory for image data
    bitmapData = (uint32_t *)malloc(bufferLength);
    
    if(!bitmapData) {
        NSLog(@"Error allocating memory for bitmap\n");
        CGColorSpaceRelease(colorSpace);
        return NULL;
    }
    
    //Create bitmap context
    
    context = CGBitmapContextCreate(bitmapData, 
            width, 
            height, 
            bitsPerComponent, 
            bytesPerRow, 
            colorSpace, 
            kCGImageAlphaPremultipliedLast);    // RGBA
    if(!context) {
        free(bitmapData);
        NSLog(@"Bitmap context not created");
    }
    
    CGColorSpaceRelease(colorSpace);
    
    return context;    
}

+ (UIImage *) convertBitmapRGBA8ToUIImage:(unsigned char *) buffer 
        withWidth:(int) width
       withHeight:(int) height {
    
    
    size_t bufferLength = width * height * 4;
    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer, bufferLength, NULL);
    size_t bitsPerComponent = 8;
    size_t bitsPerPixel = 32;
    size_t bytesPerRow = 4 * width;
    
    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
    if(colorSpaceRef == NULL) {
        NSLog(@"Error allocating color space");
        CGDataProviderRelease(provider);
        return nil;
    }
    
    CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast;
    CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
    
    CGImageRef iref = CGImageCreate(width, 
                height, 
                bitsPerComponent, 
                bitsPerPixel, 
                bytesPerRow, 
                colorSpaceRef, 
                bitmapInfo, 
                provider,    // data provider
                NULL,        // decode
                YES,            // should interpolate
                renderingIntent);
        
    uint32_t* pixels = (uint32_t*)malloc(bufferLength);
    
    if(pixels == NULL) {
        NSLog(@"Error: Memory not allocated for bitmap");
        CGDataProviderRelease(provider);
        CGColorSpaceRelease(colorSpaceRef);
        CGImageRelease(iref);        
        return nil;
    }
    
    CGContextRef context = CGBitmapContextCreate(pixels, 
                 width, 
                 height, 
                 bitsPerComponent, 
                 bytesPerRow, 
                 colorSpaceRef, 
                 bitmapInfo); 
    
    if(context == NULL) {
        NSLog(@"Error context not created");
        free(pixels);
    }
    
    UIImage *image = nil;
    if(context) {
        
        CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, width, height), iref);
        
        CGImageRef imageRef = CGBitmapContextCreateImage(context);
        
        // Support both iPad 3.2 and iPhone 4 Retina displays with the correct scale
        if([UIImage respondsToSelector:@selector(imageWithCGImage:scale:orientation:)]) {
            float scale = [[UIScreen mainScreen] scale];
            image = [UIImage imageWithCGImage:imageRef scale:scale orientation:UIImageOrientationUp];
        } else {
            image = [UIImage imageWithCGImage:imageRef];
        }
        
        CGImageRelease(imageRef);    
        CGContextRelease(context);    
    }
    
    CGColorSpaceRelease(colorSpaceRef);
    CGImageRelease(iref);
    CGDataProviderRelease(provider);
    
    if(pixels) {
        free(pixels);
    }    
    return image;
}

@end