[Mapserver-users] Geting Image X and Y for dynamically-added points

[Chip Hankley]

Erich -

You just need to work backwards. You will know the extent of your image
in real coordinates, and the size of your image in pixels. Once you know
these, it's pretty straightforward to solve for the pixel coordinates:

ImgX = ((MapX - MapMinX)/(MapMaxX - MapMinX)) * ImgWidth

The components of this are:
((MapX - MapMinX)/(MapMaxX - MapMinX)) gives you the % in the X
direction, multiplied by the ImgWidth gives you the pixel number

so if you're point is located 50% along the current mapextent, and your
image is 500 pixels wide, the ImgX location will be 0.5 * 500 = 250.

Do a similar thing for ImgY, but remember that ImgY STARTS at the top
and increases down.

Chip

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