Calculate brightness of Android Bitmap

gistfile1.java

/*
Calculates the estimated brightness of an Android Bitmap.
pixelSpacing tells how many pixels to skip each pixel. Higher values result in better performance, but a more rough estimate.
When pixelSpacing = 1, the method actually calculates the real average brightness, not an estimate.
This is what the calculateBrightness() shorthand is for.
Do not use values for pixelSpacing that are smaller than 1.
*/
public int calculateBrightnessEstimate(android.graphics.Bitmap bitmap, int pixelSpacing) {
	int R = 0; int G = 0; int B = 0;
	int height = bitmap.getHeight();
	int width = bitmap.getWidth();
	int n = 0;
	int[] pixels = new int[width * height];
	bitmap.getPixels(pixels, 0, width, 0, 0, width, height);
	for (int i = 0; i < pixels.length; i += pixelSpacing) {
		int color = pixels[i];
		R += Color.red(color);
		G += Color.green(color);
		B += Color.blue(color);
		n++;
	}
	return (R + B + G) / (n * 3);
}

public int calculateBrightness(android.graphics.Bitmap bitmap) {
	calculateBrightnessEstimate(bitmap, 1);
}

I know this is a bit of an old one, but can ask what sort of range i should see returned from this? In bright images i'm seeing values above 100 and below -100. Darker images seem to be within that range. For now, I am just using Math.abs(), but am not sure what to expect from it. Thanks.

Here, the brightness returned is between 0 and 255, where 0 is returned for a pure black image and 255 for a white one.

Thanks, it is awesome, but can you provide the calculation of colorfulness or blur? it uses std of R,G,B but implementing in java is very hard...T.T

nice