[Qt-interest] [OT] RE: Fast displaying of 8bit images

[Oliver.Knoll at comit.ch]

Hi Pavel,

Pavel Koshevoy wrote on Tuesday, March 31, 2009 9:16 PM:

> ...  On some platforms (OSX) there exist OpenGL
> extensions that avoid copying texture data from main memory to the
> graphics card memory, you may want to use that.     

I am also investigating how to use OpenGL to accelerate image scaling: my first naive approach - using a QPainter on top of an OGLWidget - showed that the bottleneck is the actual data transfer from CPU <-> GPU (I was testing with images up to 4096 x 4096).

I know that there are ways like http://www.songho.ca/opengl/gl_pbo.html (Pixel Buffer Object) to transer memory between the CPU <-> GPU.

Do you remember these extension names you where mentioning? Are they part of OpenGL 3.0 now by any chance? Or are they at least available on Windows and Linux as well (for certain drivers at least)?

And does that only help for "displaying" such "textures", or could they also remain in the GPU memory for scaling (I don't even need to display the scaled images, all I want is to scale a photo as quickly as possible, and then write it to disk [in batch mode: one photo after another])?


Some hints and links to relevant pages highly appreciated.
  Oliver
-- 
Oliver Knoll
Dipl. Informatik-Ing. ETH
COMIT AG - ++41 79 520 95 22