glTexImage2D

NAME

glTexImage2D -- specify a two-dimensional texture image

C SPECIFICATION

void glTexImage2D(GLenum target,
                  GLint level,
                  GLint components,
                  GLsizei width,
                  GLsizei height,
                  GLint border,
                  GLenum format,
                  GLenum type,
                  const GLvoid *pixels)

PARAMETERS

target: Specifies the target texture. Must be GL_TEXTURE_2D.
level: Specifies the level-of-detail number. Level 0 is the base image level. Level n is the nth mipmap reduction image.
components: Specifies the number of color components in the texture. Must be 1, 2, 3, or 4.
width: Specifies the width of the texture image. Must be 2^n + 2 * (border) for some integer n.
height: Specifies the height of the texture image. Must be 2^m + 2 * (border) for some integer m.
border: Specifies the width of the border. Must be either 0 or 1.
format: Specifies the format of the pixel data. The following symbolic values are accepted: GL_COLOR_INDEX, GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_RGBA, GL_LUMINANCE, and GL_LUMINANCE_ALPHA.
type: Specifies the data type of the pixel data. The following symbolic values are accepted: GL_UNSIGNED_BYTE, GL_BYTE, GL_BITMAP, GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT, GL_INT, and GL_FLOAT.
pixels: 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 enabled. Two-dimensional texturing is enabled and disabled using glEnable and glDisable with argument GL_TEXTURE_2D.

Texture images are defined with glTexImage2D. The arguments describe the parameters of the texture image, such as height, width, width of the border, level-of-detail number (see glTexParameter), and number of color componenents provided. The last three arguments describe the way the image is represented in memory, and they are identical to the pixel formats used for glDrawPixels.

Data is read from pixels as a sequence of signed or unsigned bytes, shorts, or longs, or single-precision floating-point values, depending on type. These values are grouped into sets of one, two, three, or four values, depending on format, to form an element. If type is GL_BITMAP, the data is considered as a string of unsigned bytes (and format must be GL_COLOR_INDEX). Each data byte is treated as eight 1-bit elements, with bit ordering determined by GL_UNPACK_LSB_FIRST (see glPixelStore).

format determines the composition of each element in pixels and selects the target frame buffer. It can assume one of nine symbolic values:

GL_COLOR_INDEX: Each element is a single value, a color index. It is converted to fixed point (with an unspecified number of zero bits to the right of the binary point), shifted left or right depending on the value and sign of GL_INDEX_SHIFT, and added to GL_INDEX_OFFSET (see glPixelTransfer). The resulting index is converted to a set of color components using the GL_PIXEL_MAP_I_TO_R, GL_PIXEL_MAP_I_TO_G, GL_PIXEL_MAP_I_TO_B, and GL_PIXEL_MAP_I_TO_A tables, and clamped to the range [0, 1].
GL_RED: Each element is a single red component. It is converted to floating point and assembled into an RGBA element by attaching 0.0 for green and blue, and 1.0 for alpha. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0, 1] (see glPixelTransfer).
GL_GREEN: Each element is a single green component. It is converted to floating point and assembled into an RGBA element by attaching 0.0 for red and blue, and 1.0 for alpha. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0, 1] (see glPixelTransfer).
GL_BLUE: Each element is a single blue component. It is converted to floating point and assembled into an RGBA element by attaching 0.0 for red and green, and 1.0 for alpha. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0, 1] (see glPixelTransfer).
GL_ALPHA: Each element is a single alpha component. It is converted to floating point and assembled into an RGBA element by attaching 0.0 for red, green and blue. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0, 1] (see glPixelTransfer).
GL_RGB: Each element is an RGB triple. It is converted to floating point and assembled into an RGBA element by attaching 1.0 for alpha. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0, 1] (see glPixelTransfer).
GL_RGBA,: Each element contains all four components. Each component is multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0, 1] (see glPixelTransfer).
GL_LUMINANCE: Each element is a single luminance value. It is converted to floating point, then assembled into an RGBA element by replicating the luminance value three times for red, green, and blue and attaching 1.0 for alpha. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0, 1] (see glPixelTransfer).
GL_LUMINANCE_ALPHA: Each element is a luminance/alpha pair. It is converted to floating point, then assembled into an RGBA element by replicating the luminance value three times for red, green, and blue. Each component is then multiplied by the signed scale factor GL_c_SCALE, added to the signed bias GL_c_BIAS, and clamped to the range [0, 1] (see glPixelTransfer).

Please refer to the glDrawPixels reference page for a description of the acceptable values for the type parameter.

A texture image can have up to four components per texture element, depending on components. A one-component texture image uses only the red component of the RGBA color extracted from pixels. A two-component image uses the R and A values. A three-component image uses the R, G, and B values. A four-component image uses all of the RGBA components

NOTES

Texturing has no effect in color index mode.

The texture image can be represented by the same data formats as the pixels in a glDrawPixels command, except that GL_STENCIL_INDEX and GL_DEPTH_COMPONENT cannot be used. glPixelStore and glPixelTransfer modes affect texture images in exactly the way they affect glDrawPixels.

A texture image with zero height or width indicates the null texture. If the null texture is specified for level-of-detail 0, it is as if texturing were disabled.

ERRORS

GL_INVALID_ENUM is generated when target is not GL_TEXTURE_2D.

GL_INVALID_ENUM is generated when format is not an accepted format constant. Format constants other than GL_STENCIL_INDEX and GL_DEPTH_COMPONENT are accepted.

GL_INVALID_ENUM is generated when type is not a type constant.

GL_INVALID_ENUM is generated if type is GL_BITMAP and format is not GL_COLOR_INDEX.

GL_INVALID_VALUE is generated if level is less than zero or greater than ld(max) where max is the returned value of GL_MAX_TEXTURE_SIZE.

GL_INVALID_VALUE is generated if components is not 1, 2, 3, or 4.

GL_INVALID_VALUE is generated if width or height is less than zero or greater than 2 + GL_MAX_TEXTURE_SIZE, or if it cannot be represented as 2^k + 2 * (border) for some integer value of k.

GL_INVALID_VALUE is generated if border is not 0 or 1.

GL_INVALID_OPERATION is generated if glTexImage2D is executed between the execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS

glGetTexImage
glIsEnabled with argument GL_TEXTURE_2D