Question

I have a point in the following coordinate system:

Java AWT:

0,0|------------------------|
   |                        |
   |  (middle p. 400,300)   |
   |                        |
   |------------------------|800,600

and I want to convert it to the following system:

OpenGL

  50,50|------------------------|
       |                        |
       |     (middle p. 0,0)    |
       |                        |
       |------------------------|-50,-50

Any idea how can I do it?

Answer 1

In general, what you want to do is convert from a (rectangular) coordinate system A to coordinate system B.

First map the source coordinate system, A to a normalized range [0, 1]:

double nx = x / (x1 - x0);
double ny = y / (y1 - y0);

Where (x0, y0) is the top left corner and (x1, y1) is the bottom right corner. Then map it to the new coordinate system:

double px = X0 + nx * (X1 - X0);
double py = Y0 + ny * (Y1 - Y0);

Where (X0, Y0) is the top left corner of your new coordinate system and (X1, Y1) is the bottom right corner of the new coordinate system.

This will work for any two rectangular coordinate systems.