Re: [Openexr-devel] Invert lines during reading process ?

[Peter N]

Bob, that'll flip your geometry in the Y axis but what Gernot is talking about is flipping the image data before uploading it as a texture to OpenGL with glTexImage2D (or similar).

I personally would suggest flipping it in main memory. This is what I'm doing, and loading the EXR is already long enough that I pretty much didnt notice the flipping I'm doing afterwards. I would suggest trying to call memcpy instead of working per byte and all that, but it should be quite fast for even a several mb image!

Good luck

-Peter

On 12/5/05, Bob Friesenhahn <address@hidden> wrote:

The example at
http://www-h.eng.cam.ac.uk/help/tpl/graphics/using_glut.html seems to
include some clues.  It includes.

   glScalef(1, -1, 1);           /* Invert Y axis so increasing Y goes down. */
   glTranslatef(0, -h, 0);       /* Shift origin up to upper-left corner. */

Now I just need to try this out in my own little test program. :-)

Bob

On Sun, 4 Dec 2005, Gernot Ziegler wrote:

> Hej !
>
> OpenGL convention requires me to upload images upside down into the
> texture data buffer, that is, I need to read the EXR image from the bottom
> up - is there a way to do this more efficiently than to read the lines one
> by one (the headers lineorder attribute is only changeable for writing
> files, correct ?) ?
>
> If only the line-by-line reading remains:
> Should I maybe y-flip the data in main memory instead ? (Main memory is
> not an issue :-) )
>
> Servus,
>  Gernot
>
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======================================
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/


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