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 and zoom effect, to achieve by dragging the mouse to adjust the size of the layer (width height). Example selection effect.

The drag and zoom ratio of the general selection of the box is more complex, can set the eight positions (direction) of the fixed trigger point, can set the minimum range, the maximum range and scale.

Here also has a simplified version of the SimpleResize, easy to learn.