Floyd-Steinberg Dithering for Kotlin Android

gistfile1.kt

fun dithering(bitmap: Bitmap) {
    val height: Int = bitmap.getHeight()
    val width: Int = bitmap.getWidth()
    val colors = 3
    val threshold = 255/colors

    for (x in 0 until width) {
        for (y in 0 until height) {
            val pixel = bitmap.getPixel(x, y)
            var alpha = Color.alpha(pixel)
            var originalColor = Color.blue(pixel)
            var newColor = originalColor/threshold*threshold
            bitmap.setPixel(x, y, Color.argb(alpha, newColor, newColor, newColor))

            var quantizationError = originalColor - newColor
            addColor(bitmap,x+1, y, quantizationError*7/16)
            addColor(bitmap,x-1, y+1, quantizationError*3/16)
            addColor(bitmap,x, y+1, quantizationError*5/16)
            addColor(bitmap,x+1, y+1, quantizationError*1/16)
        }
    }
}

private fun addColor(bitmap: Bitmap, x: Int, y :Int, change:Int) {
    if (x < 0 || y < 0){
        return
    }
    if (x >= bitmap.width || y >= bitmap.height){
        return
    }
    val pixel = bitmap.getPixel(x, y)
    var alpha = Color.alpha(pixel)
    var originalColor = Color.blue(pixel)
    var newColor = originalColor+change
    if (newColor > 255) {
        newColor = 255
    }
    bitmap.setPixel(x, y, Color.argb(alpha, newColor, newColor, newColor))
}