Bitmap set contrast and brightness Android example

////www.apache.org/licenses/LICENSE-2.0
        private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        private ColorMatrix mCM = new ColorMatrix();
        private Bitmap mBitmap;
        private float mSaturation;
        private float mAngle;
//..........
mBitmap = BitmapFactory.decodeResource(context.getResources(),
                                                   R.drawable.my_image);
//..........
        private static void setContrastScaleOnly(ColorMatrix cm, float contrast) {
            float scale = contrast + 1.f;
               float translate = (-.5f * scale + .5f) * 255.f;
            cm.set(new float[] {
                   scale, 0, 0, 0, 0,
                   0, scale, 0, 0, 0,
                   0, 0, scale, 0, 0,
                   0, 0, 0, 1, 0 });
        }
       private static void setContrast(ColorMatrix cm, float contrast) {
            float scale = contrast + 1.f;
               float translate = (-.5f * scale + .5f) * 255.f;
            cm.set(new float[] {
                   scale, 0, 0, 0, translate,
                   0, scale, 0, 0, translate,
                   0, 0, scale, 0, translate,
                   0, 0, 0, 1, 0 });
        }
        
        private static void setContrastTranslateOnly(ColorMatrix cm, float contrast) {
            float scale = contrast + 1.f;
               float translate = (-.5f * scale + .5f) * 255.f;
            cm.set(new float[] {
                   1, 0, 0, 0, translate,
                   0, 1, 0, 0, translate,
                   0, 0, 1, 0, translate,
                   0, 0, 0, 1, 0 });
        }

       @Override protected void onDraw(Canvas canvas) {
            Paint paint = mPaint;
            float x = 20;
            float y = 20;
            
            canvas.drawColor(Color.WHITE);
            
            paint.setColorFilter(null);
            canvas.drawBitmap(mBitmap, x, y, paint);
            
            ColorMatrix cm = new ColorMatrix();
            
            mAngle += 2;
            if (mAngle > 180) {
                mAngle = 0;
            }
            
            //convert our animated angle [-180...180] to a contrast value of [-1..1]
            float contrast = mAngle / 180.f;
            
            setContrast(cm, contrast);
            paint.setColorFilter(new ColorMatrixColorFilter(cm));
            canvas.drawBitmap(mBitmap, x + mBitmap.getWidth() + 10, y, paint);
            
            setContrastScaleOnly(cm, contrast);
            paint.setColorFilter(new ColorMatrixColorFilter(cm));
            canvas.drawBitmap(mBitmap, x, y + mBitmap.getHeight() + 10, paint);
            
            setContrastTranslateOnly(cm, contrast);
            paint.setColorFilter(new ColorMatrixColorFilter(cm));
            canvas.drawBitmap(mBitmap, x, y + 2*(mBitmap.getHeight() + 10),
                              paint);
            
            invalidate();
        }
    }