android 教你怎么把图片变成灰色

public static  Bitmap createBitmap(Bitmap bitmap) {
int width = bitmap.getWidth();
int height = bitmap.getHeight();
Bitmap faceIconGreyBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(faceIconGreyBitmap);
Paint paint = new Paint();
ColorMatrix colorMatrix = new ColorMatrix();
colorMatrix.setSaturation(0.1f);
ColorMatrixColorFilter colorMatrixFilter = new ColorMatrixColorFilter(colorMatrix);
paint.setColorFilter(colorMatrixFilter);
canvas.drawBitmap(bitmap, 0, 0, paint);
return faceIconGreyBitmap;

}

就这代码就够了,可以好好看看ColorMatrix 和ColorMatrixColorFilter这二个类有什么方法