Re: glReadPixels and viewport problem

Paulo,

Try the following before calling glReadPixels:

  glPixelStorei(GL_PACK_ALIGNMENT, 1);

I believe it defaults to 4, which is not a divisor of 250.

BTW, I did not remember being subscribed to linux-opengl! Is the list still 
active?

Regards,
Marten


On Thursday 27 November 2003 00.35, Paulo Jorge de Oliveira Cantante de Matos 
wrote:
> Hi all,
>
> I'm developing an application in which I get the viewport through
> glReadPixels and then I write it in to a PPM file. A situation depending
> on the viewport size arises. If the viewport is 250x250, the buffer
> returned from glReadPixels shows the viewport in 'italic' (the image is
> incorrect), a vertical line comes as a diagonal for example. However, if
> size is 500x500, everything is fine. Other similar situations arise
> depending on the viewport size. This is indeed strange, I've not set any
> state variable relating to glReadPixels, do I need to set or enable any
> special variable? Is this a known issue?
>
> I've decided not to include any code, if you would like some code to
> test it, I'll be happy to send it to you privately.
>
> Oh, and the problem is not in the procedure that writes the PPM file
> from the glReadPixels buffer since it was tested by some people and all
> get the same results with glReadPixels (I cannot assure you it's not in
> the PPM file but it's not probable).
>
> Best regards,

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