Get Pixel Value for GrayScale image

Question

Hello, i have tried the following code to read the pixel values of an Image (GrayScale). I am not that familiar with GrayScale Images and i know that there should be just one color component. can anybody tell me how i have to modify the following code to get the pixel values of an UIImage in Gray Scale ?

+(void) getPixelColorAtLocation:(UIImage *)img {
    UIColor* color = nil;
    CGImageRef inImage = img.CGImage;
    CGContextRef    context = NULL;
    CGColorSpaceRef colorSpace;
    void *          bitmapData;
    int             bitmapByteCount;
    int             bitmapBytesPerRow;

    // Get image width, height. We'll use the entire image.
    size_t pixelsWide = CGImageGetWidth(inImage);
    size_t pixelsHigh = CGImageGetHeight(inImage);

    // Declare the number of bytes per row. Each pixel in the bitmap in this
    // example is represented by 4 bytes; 8 bits each of red, green, blue, and
    // alpha.
    bitmapBytesPerRow   = (pixelsWide*4);
    bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);

    // Use the generic RGB color space.
    colorSpace = CGColorSpaceCreateDeviceGray();
    if (colorSpace == NULL)
    {
        fprintf(stderr, "Error allocating color space\n");
        return NULL;
    }

    // Allocate memory for image data. This is the destination in memory
    // where any drawing to the bitmap context will be rendered.
    bitmapData = malloc( bitmapByteCount );
    if (bitmapData == NULL)
    {
        fprintf (stderr, "Memory not allocated!");
        CGColorSpaceRelease( colorSpace );
        return NULL;
    }

    // Create the bitmap context. We want pre-multiplied ARGB, 8-bits
    // per component. Regardless of what the source image format is
    // (CMYK, Grayscale, and so on) it will be converted over to the format
    // specified here by CGBitmapContextCreate.
    context = CGBitmapContextCreate (bitmapData,
                                     pixelsWide,
                                     pixelsHigh,
                                     8,      // bits per component
                                     bitmapBytesPerRow,
                                     colorSpace,
                                     kCGImageAlphaNone);
    if (context == NULL)
    {
        free (bitmapData);
        fprintf (stderr, "Context not created!");
    }

    // Make sure and release colorspace before returning
    CGColorSpaceRelease( colorSpace );

            if (context == NULL) { return; /* error */ }

            size_t w = CGImageGetWidth(inImage);
            size_t h = CGImageGetHeight(inImage);
            CGRect rect = {{0,0},{w,h}}; 

            // Draw the image to the bitmap context. Once we draw, the memory
            // allocated for the context for rendering will then contain the
            // raw image data in the specified color space.
            CGContextDrawImage(context, rect, inImage); 

            // Now we can get a pointer to the image data associated with the bitmap
            // context.
            unsigned char* data = CGBitmapContextGetData (context);
            if (data != NULL) {
                //offset locates the pixel in the data from x,y.
                //4 for 4 bytes of data per pixel, w is width of one row of data.
                for (int i=0; i<w; i++) {
                    for (int j=0; j<h; j++) {
                        int offset = (4*(w*i)+j);
                        int alpha =  data[offset];
                        int red = data[offset];
                        int green = data[offset+2];
                        int blue = data[offset+3];
                        NSLog(@"offset: %i colors: RGB A %i %i %i  %i",offset,red,green,blue,alpha);

                    }
                }

            }

            // When finished, release the context
            CGContextRelease(context);
            // Free image data memory for the context
            if (data) { free(data); }

            //return color;
        }