1991-2006 Silicon Graphics, Inc.
glTexImage2D 3G
glTexImage2D specify a two-dimensional texture image

## C Specification

void `glTexImage2D` GLenum target GLint level GLint internalformat GLsizei width GLsizei height GLint border GLenum format GLenum type const GLvoid * data

## Parameters

target

  Specifies the target texture of the active texture unit. Must be `GL_TEXTURE_2D`, `GL_TEXTURE_CUBE_MAP_POSITIVE_X`, `GL_TEXTURE_CUBE_MAP_NEGATIVE_X`, `GL_TEXTURE_CUBE_MAP_POSITIVE_Y`, `GL_TEXTURE_CUBE_MAP_NEGATIVE_Y`, `GL_TEXTURE_CUBE_MAP_POSITIVE_Z`, or `GL_TEXTURE_CUBE_MAP_NEGATIVE_Z`.

level

  Specifies the level-of-detail number. Level 0 is the base image level. Level n is the nth mipmap reduction image.

internalformat

  Specifies the internal format of the texture. Must be one of the following symbolic constants: `GL_ALPHA`, `GL_LUMINANCE`, `GL_LUMINANCE_ALPHA`, `GL_RGB`, `GL_RGBA`.

width

  Specifies the width of the texture image. All implementations support 2D texture images that are at least 64 texels wide and cube-mapped texture images that are at least 16 texels wide.

height

  Specifies the height of the texture image All implementations support 2D texture images that are at least 64 texels high and cube-mapped texture images that are at least 16 texels high.

border

  Specifies the width of the border. Must be 0.

format

  Specifies the format of the texel data. Must match internalformat. The following symbolic values are accepted: `GL_ALPHA`, `GL_RGB`, `GL_RGBA`, `GL_LUMINANCE`, and `GL_LUMINANCE_ALPHA`.

type

  Specifies the data type of the texel data. The following symbolic values are accepted: `GL_UNSIGNED_BYTE`, `GL_UNSIGNED_SHORT_5_6_5`, `GL_UNSIGNED_SHORT_4_4_4_4`, and `GL_UNSIGNED_SHORT_5_5_5_1`.

data

  Specifies a pointer to the image data in memory.

## Description

Texturing maps a portion of a specified texture image onto each graphical primitive for which texturing is active. Texturing is active when the current fragment shader or vertex shader makes use of built-in texture lookup functions.

To define texture images, call `glTexImage2D`. The arguments describe the parameters of the texture image, such as height, width, level-of-detail number (see glTexParameter), and format. The last three arguments describe how the image is represented in memory.

Data is read from data as a sequence of unsigned bytes or shorts, depending on type. When type is `GL_UNSIGNED_BYTE`, each of the bytes is interpreted as one color component. When type is one of `GL_UNSIGNED_SHORT_5_6_5`, `GL_UNSIGNED_SHORT_4_4_4_4`, or `GL_UNSIGNED_SHORT_5_5_5_1`, each unsigned short value is interpreted as containing all the components for a single texel, with the color components arranged according to format. Color components are treated as groups of one, two, three, or four values, again based on format. Groups of components are referred to as texels.

width × height texels are read from memory, starting at location data. By default, these texels are taken from adjacent memory locations, except that after all width texels are read, the read pointer is advanced to the next four-byte boundary. The four-byte row alignment is specified by glPixelStorei with argument `GL_UNPACK_ALIGNMENT`, and it can be set to one, two, four, or eight bytes.

The first element corresponds to the lower left corner of the texture image. Subsequent elements progress left-to-right through the remaining texels in the lowest row of the texture image, and then in successively higher rows of the texture image. The final element corresponds to the upper right corner of the texture image.

format determines the composition of each element in data. It can assume one of these symbolic values:

`GL_ALPHA`

  Each element is a single alpha component. The GL converts it to floating point and assembles it into an RGBA element by attaching 0 for red, green, and blue. Each component is then clamped to the range [0,1].

`GL_RGB`

  Each element is an RGB triple. The GL converts it to floating point and assembles it into an RGBA element by attaching 1 for alpha. Each component is then clamped to the range [0,1].

`GL_RGBA`

  Each element contains all four components. The GL converts it to floating point, then each component is clamped to the range [0,1].

`GL_LUMINANCE`

  Each element is a single luminance value. The GL converts it to floating point, then assembles it into an RGBA element by replicating the luminance value three times for red, green, and blue and attaching 1 for alpha. Each component is then clamped to the range [0,1].

`GL_LUMINANCE_ALPHA`

  Each element is a luminance/alpha pair. The GL converts it to floating point, then assembles it into an RGBA element by replicating the luminance value three times for red, green, and blue. Each component is then clamped to the range [0,1].

Color components are converted to floating point based on the type. When type is `GL_UNSIGNED_BYTE`, each component is divided by 2 8 - 1 . When type is `GL_UNSIGNED_SHORT_5_6_5`, `GL_UNSIGNED_SHORT_4_4_4_4`, or `GL_UNSIGNED_SHORT_5_5_5_1`, each component is divided by 2 N - 1 , where N is the number of bits in the bitfield.

## Notes

internalformat must match format. No conversion between formats is supported during texture image processing. type may be used as a hint to specify how much precision is desired, but a GL implementation may choose to store the texture array at any internal resolution it chooses.

data may be a null pointer. In this case, texture memory is allocated to accommodate a texture of width width and height height. You can then download subtextures to initialize this texture memory. The image is undefined if the user tries to apply an uninitialized portion of the texture image to a primitive.

`glTexImage2D` specifies a two-dimensional or cube-map texture for the current texture unit, specified with glActiveTexture.

## Errors

`GL_INVALID_ENUM` is generated if target is not `GL_TEXTURE_2D`, `GL_TEXTURE_CUBE_MAP_POSITIVE_X`, `GL_TEXTURE_CUBE_MAP_NEGATIVE_X`, `GL_TEXTURE_CUBE_MAP_POSITIVE_Y`, `GL_TEXTURE_CUBE_MAP_NEGATIVE_Y`, `GL_TEXTURE_CUBE_MAP_POSITIVE_Z`, or `GL_TEXTURE_CUBE_MAP_NEGATIVE_Z`.

`GL_INVALID_ENUM` is generated if format or type is not an accepted value.

`GL_INVALID_VALUE` is generated if target is one of the six cube map 2D image targets and the width and height parameters are not equal.

`GL_INVALID_VALUE` is generated if level is less than 0.

`GL_INVALID_VALUE` may be generated if level is greater than log 2 ⁡ max , where max is the returned value of `GL_MAX_TEXTURE_SIZE` when target is `GL_TEXTURE_2D` or `GL_MAX_CUBE_MAP_TEXTURE_SIZE` when target is not `GL_TEXTURE_2D`.

`GL_INVALID_VALUE` is generated if internalformat is not an accepted format.

`GL_INVALID_VALUE` is generated if width or height is less than 0 or greater than `GL_MAX_TEXTURE_SIZE` when target is `GL_TEXTURE_2D` or `GL_MAX_CUBE_MAP_TEXTURE_SIZE` when target is not `GL_TEXTURE_2D`.

`GL_INVALID_VALUE` is generated if border is not 0.

`GL_INVALID_OPERATION` is generated if format does not match internalformat.

`GL_INVALID_OPERATION` is generated if type is `GL_UNSIGNED_SHORT_5_6_5` and format is not `GL_RGB`.

`GL_INVALID_OPERATION` is generated if type is `GL_UNSIGNED_SHORT_4_4_4_4` or `GL_UNSIGNED_SHORT_5_5_5_1` and format is not `GL_RGBA`.

## Associated Gets

glGet with argument `GL_MAX_TEXTURE_SIZE` or `GL_MAX_CUBE_MAP_TEXTURE_SIZE`

## See Also

glActiveTexture, glCompressedTexImage2D, glCompressedTexSubImage2D, glCopyTexImage2D, glCopyTexSubImage2D, glPixelStorei, glTexSubImage2D, glTexParameter

## Copyright

Copyright 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.