How to make certain pixels transparent on the uiimage pixel on the iPhone

- (UIImage *)processWithePixels:(UIImage*)teeImage alpha:(int)trans{

    UInt32 * teePixels;

    CGImageRef teeCGImage = [teeImage CGImage];
    NSUInteger teeWidth = CGImageGetWidth(teeCGImage);
    NSUInteger teeHeight = CGImageGetHeight(teeCGImage);

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    NSUInteger bytesPerPixel = 4;
    NSUInteger bitsPerComponent = 8;

    NSUInteger teeBytesPerRow = bytesPerPixel * teeWidth;

    teePixels = (UInt32 *)calloc(teeHeight * teeWidth, sizeof(UInt32));


    CGContextRef context = CGBitmapContextCreate(teePixels, teeWidth, teeHeight,
                                                 bitsPerComponent, teeBytesPerRow, colorSpace,
                                                 kCGImageAlphaPremultipliedLast|kCGBitmapByteOrder32Big);



    CGContextDrawImage(context, CGRectMake(0, 0, teeWidth, teeHeight), teeCGImage);

    for (NSUInteger j = 0; j < teeHeight; j++) {
        for (NSUInteger i = 0; i < teeWidth; i++) {
            UInt32 * currentPixel  = teePixels + ( j * teeWidth) + i;


            UInt32 color = *currentPixel;
            int mColor = 0;

            if(color != 0){
                if(B(color) < R(color)){
                    mColor = B(color);
                }else{
                    mColor = R(color);
                }

                if(mColor > G(color)){
                    mColor = G(color);
                }

                mColor  = 255 - mColor;
                mColor = (int)(mColor * 2);
                if(mColor > trans ){
                    mColor = trans;
                }
            }else{
                mColor = 0;
            }


            CGFloat alpha = 255 - mColor;
            UInt32 newR = R(color) - alpha;
            UInt32 newG = G(color) - alpha;
            UInt32 newB = B(color) - alpha;
            UInt32 newA = A(color) - alpha;


            newR = MAX(0,MIN(255, newR));
            newG = MAX(0,MIN(255, newG));
            newB = MAX(0,MIN(255, newB));

            *currentPixel = RGBAMake(newR, newG, newB, mColor);

        }
    }

    // // 4. Create a new UIImage
    CGImageRef newCGImage = CGBitmapContextCreateImage(context);
    UIImage * processedImage = [UIImage imageWithCGImage:newCGImage scale:1 orientation:teeImage.imageOrientation];

    // // 5. Cleanup!
    CGColorSpaceRelease(colorSpace);

    CGContextRelease(context);

    CFRelease(newCGImage);
    free(teePixels);

    return processedImage;
};