glPixelTransfer/glDrawPixels Slowdown Problem

Hi all,

I’m trying to display a bitmap using glDrawPixels and thought that I might be able to control brightness by using glPixelTransfer to add a bias to my red, green, and blue channels. It seems to be no problem on my desktop PC (which has integrated Intel 82845G graphics), but when I move the source over to our development PC (with an nVidia GeForce4 MX440) the app slows to a crawl and the GUI becomes unresponsive.

So…I was wondering if anybody has ever seen something similar, what the cause might be, and how would I remedy the situation? I was also wondering if anyone knows whether or not the bias and glPixelMap functions are hardware accelerated on an nVidia GeForce4 MX440.


It is much faster to draw 2D graphics with textured quads than with glDrawPixels. I think this is because texture objects are stored on the video card and dont have to be passed to the card each time they are drawn.

As glDrawPixels is not used a lot because it is slow, so it not well implemented on gfx cards, so it is used even less, etc.

Even with a dynamic texture, it can be faster to use a textured quad and glTexSubImage to change the texels.

Thanks for the responses…I’ll give the textured quad a try…