glTexImage2D — specify a two-dimensional texture image
void glTexImage2D( | GLenum target, |
| GLint level, | |
| GLint internalformat, | |
| GLsizei width, | |
| GLsizei height, | |
| GLint border, | |
| GLenum format, | |
| GLenum type, | |
const GLvoid * pixels); |
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.
Must be greater or equal 0.
internalformat
Specifies the color components in the
texture. Must be same as format.
The following symbolic values are accepted:
GL_ALPHA,
GL_RGB,
GL_RGBA,
GL_LUMINANCE, or
GL_LUMINANCE_ALPHA.
width
Specifies the width of the texture image. Must be
n.
All implementations support texture images that are at
least 64 texels wide.
height
Specifies the height of the texture image. Must be
m.
All implementations support texture images that are at
least 64 texels high.
border
Specifies the width of the border. Must be 0.
format
Specifies the format of the pixel data. Must be same
as 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 pixel 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.
pixels
Specifies a pointer to the image data in memory.
Texturing maps a portion of a specified texture image
onto each graphical primitive for which texturing is enabled.
To enable and disable two-dimensional texturing, call
glEnable and
glDisable
with argument GL_TEXTURE_2D.
Two-dimensional texturing is initially disabled.
To define texture images, call
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 components provided. The last three
arguments describe how the image is represented in memory.
Data is read from pixels
as a sequence of unsigned bytes or shorts, depending on
type.
These values are grouped into sets of one, two, three, or
four values, depending on format,
to form elements.
When type is
GL_UNSIGNED_BYTE, each of these bytes is
interpreted as one color component, depending on
format.
When type is one of
GL_UNSIGNED_SHORT_5_6_5,
GL_UNSIGNED_SHORT_4_4_4_4,
GL_UNSIGNED_SHORT_5_5_5_1,
each unsigned value is interpreted as containing all the components
for a single pixel, with the color components arranged according to
format.
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.
By default, adjacent pixels are taken from adjacent memory
locations, except that after all width pixels 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.
format
determines the composition of each element in
pixels.
It can assume one of the following 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.
GL_RGB
Each element is an RGB triple. The GL converts it to fixed-point or floating-point and assembles it into an RGBA element by attaching 1 for alpha.
GL_RGBA
Each element contains all four components. The GL converts it to fixed-point or floating-point.
GL_LUMINANCE
Each element is a single luminance value. The GL converts it to fixed-point or 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.
GL_LUMINANCE_ALPHA
Each element is a luminance/alpha pair. The GL converts it to fixed-point or floating point, then assembles it into an RGBA element by replicating the luminance value three times for red, green, and blue.
pixels
may be NULL. 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 the two-dimensional texture for the currently bound texture
specified with
glBindTexture,
and the current texture
unit, specified with
glActiveTexture.
GL_INVALID_ENUM is generated if
target is not
GL_TEXTURE_2D.
GL_INVALID_ENUM is generated if
format is not an accepted constant.
GL_INVALID_ENUM is generated if
type is not an accepted constant.
GL_INVALID_VALUE is generated if
level is less than 0.
GL_INVALID_VALUE may be generated if
level is greater than
max is the returned value of
GL_MAX_TEXTURE_SIZE.
GL_INVALID_VALUE is generated if
internalformat
is not an accepted constant.
GL_INVALID_VALUE is generated if
width or height
is less than 0 or greater than GL_MAX_TEXTURE_SIZE,
or if either cannot be represented as
k.
GL_INVALID_VALUE is generated if
border is not 0.
GL_INVALID_OPERATION is generated if
internalformat and
format are not the same.
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 one of
GL_UNSIGNED_SHORT_4_4_4_4, or
GL_UNSIGNED_SHORT_5_5_5_1 and
format is not
GL_RGBA.
glActiveTexture, glBindTexture, glCopyTexImage2D, glCopyTexSubImage2D, glGet, glMatrixMode, glPixelStorei, glTexEnv, glTexSubImage2D, glTexParameter
Copyright © 2003-2004 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.