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glGetTexImage

Chapter 7

218

If the selected texture image does not contain four components, the following mappings

are applied. Single-component textures are treated as RGBA buffers with red set to the

single-component value, green set to 0, blue set to 0, and alpha set to 1. Two-component

textures are treated as RGBA buffers with red set to the value of component zero, alpha

set to the value of component one, and green and blue set to 0. Finally, three-component

textures are treated as RGBA buffers with red set to component zero, green set to

component one, blue set to component two, and alpha set to 1.

To determine the required size of pixels, use glGetTexLevelParameter to determine the

dimensions of the internal texture image, then scale the required number of pixels by

the storage required for each pixel, based on format and type. Be sure to take the pixel

storage parameters into account, especially GL_PACK_ALIGNMENT.

Notes

If an error is generated, no change is made to the contents of pixels.

Errors

• GL_INVALID_ENUM is generated if target, format,ortype is not an accepted value.

• GL_INVALID_VALUE is generated if level is less than 0.

• GL_INVALID_VALUE may be generated if level is greater than $log sub 2 max$,

where $max$ is the returned value of GL_MAX_TEXTURE_SIZE.

• GL_INVALID_OPERATION is generated if glGetTexImage is executed between the

execution of glBegin and the corresponding execution of glEnd.

Associated Gets

glGetTexLevelParameter with argument GL_TEXTURE_WIDTH

glGetTexLevelParameter with argument GL_TEXTURE_HEIGHT

glGetTexLevelParameter with argument GL_TEXTURE_BORDER

glGetTexLevelParameter with argument GL_TEXTURE_COMPONENTS

glGet with arguments GL_PACK_ALIGNMENT and others

HP b2600 Reference Guide

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