[josm-dev] Plugin: Access layer pixel data

Paul Hartmann phaaurlt at googlemail.com
Tue Apr 15 20:46:36 UTC 2014

On 15.04.2014 18:24, Nick Ma. wrote:
> I'm working on a plugin like "Tracer2"[1] but which should run
> entirely embedded into JOSM.
> Therefore I'm asking for the best way to access pixel color shown in
> an active Layer[2] or ImageryLayer?

Like this (gets the pixels in the current view):

  BufferedImage image = new BufferedImage(20, 30, 
  Graphics2D g2 = image.createGraphics();
  g2.setClip(0, 0, 20, 30);
  int col = image.getRGB(5,6);

The Layer class has a paint() method as well, if you just need one layer.

> Why/Background/Next steps (that's not the question):
> To execute an edge detection[3] algorithm with the image information
> and auto detect the edges of an area currently displayed in JOSM.
> Helping to faster create buildings.

The library ImageJ might be worth a look. It is pure Java and is 
advertised as being fast.

Also lakewalker is another plugin that does a similar thing, but more 


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