Я пытаюсь преобразовать изображение в оттенки серого следующим образом:

#define bytesPerPixel 4
#define bitsPerComponent 8

-(unsigned char*) getBytesForImage: (UIImage*)pImage
{
    CGImageRef image = [pImage CGImage];
    NSUInteger width = CGImageGetWidth(image);
    NSUInteger height = CGImageGetHeight(image);

    NSUInteger bytesPerRow = bytesPerPixel * width;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    unsigned char *rawData = malloc(height * width * 4);
    CGContextRef context = CGBitmapContextCreate(rawData, width, height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
    CGColorSpaceRelease(colorSpace);

    CGContextDrawImage(context, CGRectMake(0, 0, width, height), image);
    CGContextRelease(context);

    return rawData;
}

-(UIImage*) processImage: (UIImage*)pImage
{   
    DebugLog(@"processing image");
    unsigned char *rawData = [self getBytesForImage: pImage];

    NSUInteger width = pImage.size.width;
    NSUInteger height = pImage.size.height;

    DebugLog(@"width: %d", width);
    DebugLog(@"height: %d", height);

    NSUInteger bytesPerRow = bytesPerPixel * width;

    for (int xCoordinate = 0; xCoordinate < width; xCoordinate++)
    {
        for (int yCoordinate = 0; yCoordinate < height; yCoordinate++)
        {
            int byteIndex = (bytesPerRow * yCoordinate) + xCoordinate * bytesPerPixel;

            //Getting original colors
            float red = ( rawData[byteIndex] / 255.f );
            float green = ( rawData[byteIndex + 1] / 255.f );
            float blue = ( rawData[byteIndex + 2] / 255.f );

            //Processing pixel data
            float averageColor = (red + green + blue) / 3.0f;

            red = averageColor;
            green = averageColor;
            blue = averageColor;

            //Assigning new color components
            rawData[byteIndex] = (unsigned char) red * 255;
            rawData[byteIndex + 1] = (unsigned char) green * 255;
            rawData[byteIndex + 2] = (unsigned char) blue * 255;


        }
    }

    NSData* newPixelData = [NSData dataWithBytes: rawData length: height * width * 4];
    UIImage* newImage = [UIImage imageWithData: newPixelData];

    free(rawData);

    DebugLog(@"image processed");

    return newImage;

}

Поэтому, когда я хочу преобразовать изображение, я просто вызываю processImage:

imageToDisplay.image = [self processImage: image];

Но imageToDisplay не делаетт дисплей. В чем может быть проблема?

Благодарю.