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Find average pixel color in a texture?

Started by JackOfAllTrades Aug 24, 2011 at 1:34 AM 2 replies 2.6k views

Original Post

Aug 24, 2011 at 1:34 AM

Basically I want to add together all of the pixels in a texture and divide them by the number of pixels to get the average color. Two reasons I want to do this. First I want to do this for HDR lighting effects. Second I want to do this to check if a texture is simi transparent so I can render it after I render all opaque objects. I assume this would be done in a shader but I'm not sure how to write it?

21st Century Moose

Aug 24, 2011 at 1:39 AM

If the texture is mipmapped you can get the average colour by sampling the last miplevel.

JackOfAllTrades

Aug 24, 2011 at 1:55 AM

If the texture is mipmapped you can get the average colour by sampling the last miplevel.

How do I get a pixel from the texture and how do I specify the last miplevel?

Combine glReadPixels and GL_TEXTURE_MAX_LEVEL some how?

dpadam450

Aug 24, 2011 at 4:37 PM

I think you have to bind that to your shader. You can set the maximum mip-map level on a texture so that it only binds specific mip levels. glReadPixels if you read the definition it will only copy stuff from the framebuffer, not from a texture.
[color=#1C2837][size=2]

[color=#1C2837][size=2]

[color=#1C2837][size=2]Second I want to do this to check if a texture is simi transparent so I can render it after I render all opaque objects.
[color=#1C2837][size=2][/quote]
[color=#1C2837][size=2]

[color=#1C2837][size=2]Huh? What I do is for every mesh it has a texture on it. When calling glTexImage2D(), you specify if the texture has alpha or not, so just remember that throughout your application. All meshes with an alpha texture, I know to draw last.

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