bitmapMesh

未完成，~~由于开了硬件加速 drawBitmapMesh的参数colors在API18以下是不起作用的，所以API18以下的系统上是看不到窗帘的阴影的，正在解决这个问题~~

~~according to official api guides, the parameter 'colors' of canvas.drawBitmapMesh won't work when api level lower than 18, so shadow effect is not available when api level lower than 18~~

阴影问题已解决

shadow issue solved.

无法显示阴影时的效果:

this's what it looks like when shadow effect is not available

显示出阴影时的效果(由于gif对颜色的压缩，阴影效果显示不是很好):

this's what it looks like when shadow effect works

静态效果