对齐坐标系 [英] Aligning coordinate systems

问题描述

假设我有两个坐标系，如图所示

如何对齐这个坐标系？我知道我需要翻译第二个坐标系围绕X与180度，然后将其翻译为（0，0）的第一个坐标系，但我有一些麻烦，得到错误的结果。将真正感谢任何详细的答案。

编辑：第二个坐标系的实际（0,0）与第一个坐标系的Y一样。

（a，b）。 / p>

一旦你知道了，你所需要的是：

  QPointF pos1 ; // original position 
 QTransform t; 
 t.scale（1，-1）; 
 t.translate（a，-b + 1）; 
 QPointF pos2 = pos1 * t; 
  

Let's say I have 2 coordinate systems as it is shown in image attached

How can I align this coordinate systems? I know that I need to translate second coordinate system around X with 180 grads, and then translate it to (0, 0) of the first coordinate system, but I have some troubles with doing it getting wrong results. Will really appreciate any detailed answer.

EDIT: Actually (0, 0) of second coordinate system is in the same point like Y of the first coordinate system.

解决方案

The important piece of information is where is the second coordinate system's origin - namely (a,b).

Once you know that, all you need is:

QPointF pos1; // original position
QTransform t;
t.scale(1, -1);
t.translate(a, -b+1);
QPointF pos2 = pos1 * t;

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