拖拉缩放效果，实现通过鼠标拖动来调整层的面积（宽高）大小。例如选框效果。

这里的拖拉缩放比一般的选框复杂一点，能设置八个方位（方向）的固定触发点，能设置最小范围，最大范围和比例缩放。

这里也有一个简化版的SimpleResize，方便学习。,Drag zoom effects, drag the mouse to achieve through the layer to adjust the size (width height) size. For example, the effect box. Zoom drag here than the average box a bit more complex to set up eight azimuth (direction) fixed trigger point, can set a minimum, the greatest scope and scaling. Here there is a simplified version of the SimpleResize, facilitate learning.