如何在比例之前找到比例点？

Question

我对此有一个视图和动画。我在3X 和3Y 上放大了这个视图。

pivotX 和 pivotY -> 视图中心

我想在缩放视图之前找到一个点（左，上），已经缩放了值。

 How can i find this point? ->()------------------------
                               |    ______________     |
                               |    |            |     |
                               |    |   100x50   |     |
                               |    |            |     |
                               |    --------------     |
                               |                       |
                               -------------------------

注意：坐标系为[x：从左到右，y：从上到下]

Answer 1

您可以像这样计算比例后的任何点：

// find the position relative to the pivot point
float relativeX = pointBeforeScale.x - pivotPoint.x; 
float relativeY = pointBeforeScale.y - pivotPoint.y;

// multiply the relative position by the scale
relativeX *= scale;
relativeY *= scale;

// add the pivot point to the result to get the absolute position.
float pointAfterScaleX = relativeX + pivotPoint.x;
float pointAfterScaleY = relativeY + pivotPoint.y;