Android：自定义ImageView展示大图中的指定区域并切圆角（雪碧图）

@Override
protected void onDraw(Canvas canvas)
{
Drawable drawable = getDrawable();
if (drawable instanceof BitmapDrawable)
{
Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
Paint paint = new Paint();

...//根据需要计算展示区域在大图中的位置

// 绘制大图的某个区域，左上右下
Rect src = new Rect(left, top, right, bottom);

// 绘制区域，填满控件
Rect des = new Rect(0, 0, getWidth(), getHeight());

// 圆角
Path clipPath = new Path();
clipPath.addRoundRect(new RectF(des), radius, radius, Path.Direction.CW);
canvas.clipPath(clipPath);

canvas.drawBitmap(bitmap, src, des, paint);
}
else
{
super.onDraw(canvas);
}
}