Invert and Grayscale Transformation using RenderScript

InvertAndGrayscaleTransformation.java

package your.package;

import android.content.Context;
import android.graphics.Bitmap;
import android.support.v8.renderscript.Allocation;
import android.support.v8.renderscript.Element;
import android.support.v8.renderscript.Matrix4f;
import android.support.v8.renderscript.RenderScript;
import android.support.v8.renderscript.ScriptIntrinsicColorMatrix;

import com.squareup.picasso.Transformation;

class InvertAndGrayscaleTransformation implements Transformation {
    private static final Matrix4f TRANSFORMATION_MATRIX = new Matrix4f(new float[]
            {
                    -0.33f, -0.33f, -0.33f, 1.0f,
                    -0.59f, -0.59f, -0.59f, 1.0f,
                    -0.11f, -0.11f, -0.11f, 1.0f,
                    1.0f, 1.0f, 1.0f, 1.0f
            });
    private final RenderScript mRender;

    public InvertAndGrayscaleTransformation(Context context) {
        mRender = RenderScript.create(context);
    }

    @Override
    public Bitmap transform(Bitmap source) {
        final Bitmap result = source.copy(source.getConfig(), true);
        Allocation input = Allocation.createFromBitmap(mRender, source,
                Allocation.MipmapControl.MIPMAP_NONE, Allocation.USAGE_SCRIPT);
        Allocation output = Allocation.createTyped(mRender, input.getType());

        // Inverts and grayscales the image
        final ScriptIntrinsicColorMatrix inverter = ScriptIntrinsicColorMatrix.create(mRender, Element.U8_4(mRender));
        inverter.setColorMatrix(TRANSFORMATION_MATRIX);
        inverter.forEach(input, output);
        output.copyTo(result);

        source.recycle();
        mRender.destroy();
        return result;
    }

    @Override
    public String key() {
        return "invertAndGrayscale()";
    }
}