Hello Android-Bitmapを白黒に変換したグレースケールとフィレット効果

/** 
 *         .
 * 
 */
public class ImageTools {
    
    /***//**
     *     ,      
     * @param bmpOriginal      
     * @return       
     */
    public static Bitmap toGrayscale(Bitmap bmpOriginal) {
        int width, height;
        height = bmpOriginal.getHeight();
        width = bmpOriginal.getWidth();    

        Bitmap bmpGrayscale = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
        Canvas c = new Canvas(bmpGrayscale);
        Paint paint = new Paint();
        ColorMatrix cm = new ColorMatrix();
        cm.setSaturation(0);
        ColorMatrixColorFilter f = new ColorMatrixColorFilter(cm);
        paint.setColorFilter(f);
        c.drawBitmap(bmpOriginal, 0, 0, paint);
        return bmpGrayscale;
    }
    
    
    /***//**
     *        
     * @param bmpOriginal   
     * @param pixels     
     * @return       
     */
    public static Bitmap toGrayscale(Bitmap bmpOriginal, int pixels) {
        return toRoundCorner(toGrayscale(bmpOriginal), pixels);
    }
    
    /***//**
     *        
     * @param bitmap        
     * @param pixels      
     * @return     
     */
    public static Bitmap toRoundCorner(Bitmap bitmap, int pixels) {

        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap
                .getHeight(), Config.ARGB_8888);
        Canvas canvas = new Canvas(output);

        final int color = 0xff424242;
        final Paint paint = new Paint();
        final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
        final RectF rectF = new RectF(rect);
        final float roundPx = pixels;

        paint.setAntiAlias(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(color);
        canvas.drawRoundRect(rectF, roundPx, roundPx, paint);

        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, paint);

        return output;
    }

    
    /***//**
     *        BitampDrawable
     * @param bitmapDrawable 
     * @param pixels 
     * @return
     */
    public static BitmapDrawable toRoundCorner(BitmapDrawable bitmapDrawable, int pixels) {
        Bitmap bitmap = bitmapDrawable.getBitmap();
        bitmapDrawable = new BitmapDrawable(toRoundCorner(bitmap, pixels));
        return bitmapDrawable;
    }
}