Android Canvas变换操做备忘

 

Bitmap buffer = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(buffer);
/**
 * 将bitmap的左上角放到canvas的(0, 0)点
 * 向右移动40，向上移动40
 * 以直线y=0，翻转
 */
canvas.save();
canvas.scale(1, -1, 0, 0);
canvas.translate(40, -40);
canvas.drawBitmap(bitmap, 0, 0, null);
canvas.restore();