Seadragon ajax fix coordinates system

Question

I'm trying Seadragon Ajax with coordinates system in order to show in my website large images with big resolution . I would to view a part of this image knowing their coordinates. The problem is that when I make zoom or drag the image , coordinates no longer correspond to the same part of the image. I try with some code but no way.I need that coordinates system is fix for all the image . As i can do? Thanks

Answer 1

Sure, no problem. You have to transform the "real" pixelbased coordinate to the seadragon point-coordinate.

"Seadragon Ajax uses a normalized coordinate system. The top-left of the image is always at the origin (0, 0) while the width of the image is always 1. The height of the image is dependant on the aspect ratio, so an image which is half as tall as it is wide will have a height of 0.5"

So, if you know that your image is 500x500px, then point 1,1 = 500px,500px and 0.5,0.5 = 250px,250px.

Convert by writing a function like this:

var my_position_x=333; // the position you want to get point for
var my_position_y=666; // the position you want to get point for
var width=500;
var height=500;
var pointx=1/width * my_position_x;
var pointy=1/height * my_position_y;