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);
}

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