RGBToolkit.kt

package orllewin.lutcreator


import android.graphics.Bitmap
import com.google.android.renderscript.LookupTable
import com.google.android.renderscript.Toolkit

/**
 *
 * Fast Bitmap colour channel filtering
 * For use with the RenderScript intrinsics replacement Toolkit:
 * https://github.com/android/renderscript-intrinsics-replacement-toolkit
 *
 * This offers basic linear RGB filtering, but the toolkit LookupTable would support more
 * complex RGB channel curves too.
 *
 */
class RGBToolkit {

    private val rgbTable = LookupTable()

    fun updateRed(red: Int){
        repeat(256){ i ->
            rgbTable.red[i] = ((i/100f) * red).toInt().toByte()
        }
    }

    fun updateGreen(green: Int){
        repeat(256){ i ->
            rgbTable.green[i] = ((i/100f) * green).toInt().toByte()
        }
    }

    fun updateBlue(blue: Int){
        repeat(256){ i ->
            rgbTable.blue[i] = ((i/100f) * blue).toInt().toByte()
        }
    }

    fun updateRGB(r: Int, g: Int, b: Int){
        repeat(256){ i ->
            rgbTable.red[i] = ((i/100f) * r).toInt().toByte()
            rgbTable.green[i] = ((i/100f) * g).toInt().toByte()
            rgbTable.blue[i] = ((i/100f) * b).toInt().toByte()
        }
    }

    fun process(source: Bitmap): Bitmap = Toolkit.lut(source, rgbTable)
}