Fastest way to check if NSImage is a template image

Let's say you have a NSImage with NSBitmapImageRep (raster image) of 16x16 pixels. It can be a color image or contain only black pixels with alpha channel.

When it only has black pixels, I can set .isTemplate for the NSImage and handle it correspondingly.

The question is - how do you quickly detect it has black pixels only?

What is the fastest way to check if provided image is a template?

Here is how I do it. It works, but requires moving through all the pixels and check them one-by-one. Even with 16x16 size it takes about a second for 10-20 images to process. So I am looking for a more optimized approach:

+ (BOOL)detectImageIsTemplate:(NSImage *)image
{
    BOOL result = NO;
    
    if (image)
    {
        // If we have a valid image, assume it's a template until we face any non-black pixel
        result = YES;
        
        NSSize imageSize = image.size;
        NSRect imageRect = NSMakeRect(0, 0, imageSize.width, imageSize.height);
        CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
        
        CGContextRef ctx = CGBitmapContextCreate(NULL,
                                                 imageSize.width,
                                                 imageSize.height,
                                                 8,
                                                 0,
                                                 colorSpace,
                                                 kCGImageAlphaPremultipliedLast);
        
        NSGraphicsContext* gctx = [NSGraphicsContext graphicsContextWithCGContext:ctx flipped:NO];
        [NSGraphicsContext setCurrentContext:gctx];
        [image drawInRect:imageRect];
        
        // ......................................................
        
        size_t width = CGBitmapContextGetWidth(ctx);
        size_t height = CGBitmapContextGetHeight(ctx);

        uint32_t* pixel = (uint32_t*)CGBitmapContextGetData(ctx);

        for (unsigned y = 0; y < height; y++)
        {
            for (unsigned x = 0; x < width; x++)
            {
                uint32_t rgba = *pixel;

                uint8_t red   = (rgba & 0x000000ff) >> 0;
                uint8_t green = (rgba & 0x0000ff00) >> 8;
                uint8_t blue  = (rgba & 0x00ff0000) >> 16;
                
                if (red != 0 || green != 0 || blue != 0)
                {
                    result = NO;
                    break;
                }

                pixel++; // Next pixel
            }
            
            if (result == NO) break;
        }
        
        // ......................................................
        
        [NSGraphicsContext setCurrentContext:nil];
        CGContextRelease(ctx);
        CGColorSpaceRelease(colorSpace);
    }
    
    return result;
}