[Gdal-dev] plotting data

Roger Persson rogper at bredband.net
Sun Sep 19 05:49:08 EDT 2004


Thanks for the hint. But what projection are am suppose to use? If I 
project the (lat, long, height)-coordinate onto a "Oblique 
Stereographic" (x, y, z)-surface, then I must project a second time 
onto a graphics device coordinate system (or OpenGL coordinate system) 
before rendering. Is it up to me to calculate the latter (affine) 
transformation, or is there an utility to do that ?


2004-09-19 kl. 00.00 skrev Chapman, Martin:

> Roger,
> There are several ways to draw your points in a window.  All the ones 
> I know, at a minimum, use the "graphics device context".  The DC 
> (device context) or objects that derive from it, have methods to draw 
> to a window that take x, y as parameters.  It also lets you control 
> things like line width, fill color, etc.  In addition to that, the 
> device context can also be used to pass control of the rendering to a 
> third party graphics library like OpenGL.  There is a lot of good code 
> on the internet that shows how to do this for your specific platform.
> With that said, I would search google for how to draw points in a 
> window using the device context or opengl on Mac OSX.  Once you get 
> that plumbing hooked up it will be obvious how to feed the points to 
> your screen from OGR.
> I would strongly recommend using OpenGL for vector, not for raster 
> though...always use the device context for rasters unless you want to 
> project the image into a vector map.  Go to http://nehe.gamedev.net/ 
> and try some of the cross-platform examples for OpenGL as well.

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