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glReadPixels

Started by dpadam450 Sep 13, 2006 at 11:14 PM 3 replies 800+ views

Original Post

Sep 13, 2006 at 11:14 PM

My window is 256x256; I draw a full red quad covering the screen. My code: float data[256]; glReadPixels(0,0, 1, 256, GL_RED, GL_FLOAT, &data); I output the data and the last 20 or so pixels that it reads aren't "1" but stuff like: 5.94044e-039 5.88879e-039 Any idea what I did wrong?

bakery2k1

Sep 14, 2006 at 7:15 AM

Are you sure the client area of your window (i.e., excluding the borders) is 256x256?

dpadam450

Sep 14, 2006 at 7:40 PM

When I call the CreateWindow function (or whichever one it is) I told windows to give me 256x256, does it count the top of the window (blue part) as part of the window? Cuz that would make sense then since its about 20 pixels.

dpadam450

Sep 14, 2006 at 7:44 PM

Didn't think I had time to check that, but I answered my own question on that.

bakery2k1

Sep 16, 2006 at 7:37 AM

The window size passed to CreateWindow includes the border. To calculate the correct size to pass in order to get a 256x256 client area, use the AdjustWindowRect function.

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