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Pixel data from texture?

Started by MGB Mar 4, 2007 at 3:01 PM 7 replies 1.5k views

Original Post

Mar 4, 2007 at 3:01 PM

Does anyone know how/if I can read the pixel data of a texture in OpenGL? I want to check my render-to-texture stuff is working, but all the commands I can see are for putting data *into* textures..?

dpadam450

523

dpadam450

Mar 4, 2007 at 3:34 PM

Well if its a texutre, just strap it to a quad and render that.

daniel_i_l

Mar 4, 2007 at 3:41 PM

If you want the pixel data without passing the texture to the graphics card and wasting space you can take the data pointer (from whatever you use to load the texture) and then iterate through it and delete it before passing it on.

MGB

Author

MGB

Mar 4, 2007 at 3:54 PM

Ah, the FBO stuff did it... ta!

glReadBuffer(GL_COLOR_ATTACHMENT0_EXT);char readBuff[texSize*texSize*3];glReadPixels(0,0,texSize,texSize,GL_RGB,GL_UNSIGNED_BYTE,readBuff);

umm not too sure what you meant there, daniel...

Nathan Baum

Mar 4, 2007 at 5:22 PM

You can also use glGetTexImage

MGB

Author

MGB

Mar 5, 2007 at 5:10 AM

Quote:
Original post by Nathan Baum
You can also use glGetTexImage

Tsk - I actually looked through the Red Book for something like this and never saw it :o
Must prioritise sleep over gamedev some time :-/

[Edited by - Aph3x on March 5, 2007 5:10:56 AM]

daniel_i_l

Mar 5, 2007 at 5:58 AM

Quote:
Original post by Aph3x
umm not too sure what you meant there, daniel...

When you load a texture you call the following commands:

GLuint texture;Texture = LoadPicture("pic.bmp"); //whatever you load the pic withglGenTextures(1, &texture);					glBindTexture(GL_TEXTURE_2D, texture);glTexImage2D(GL_TEXTURE_2D, 0, 3, Texture->sizeX, Texture->sizeY, 0, GL_RGB,GL_UNSIGNED_BYTE, Texture->data);free(Texture->data);

Now if you only want the data without actually generating a texture you can skip everything except the first line and use TextureData->data and the free it.

MGB

Author

MGB

Mar 5, 2007 at 7:27 AM

Ah I see what you mean, but I was wanting to check that the right image was getting *into* my texture which was being rendered at runtime.

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