GLTEXIMAGE2D(3gl)GLTEXIMAGE2D(3gl)NAME
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 *pixels )
PARAMETERS
target Specifies the target texture. Must be one of GL_TEX‐
TURE_2D, GL_TEXTURE_CUBE_MAP_POSITIVE_X, GL_TEX‐
TURE_CUBE_MAP_NEGATIVE_X, GL_TEXTURE_CUBE_MAP_POSI‐
TIVE_Y, GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, GL_TEX‐
TURE_CUBE_MAP_POSITIVE_Z, GL_TEXTURE_CUBE_MAP_NEGA‐
TIVE_Z, GL_PROXY_TEXTURE_2D, GL_PROXY_TEXTURE_CUBE_MAP,
or GL_DETAIL_TEXTURE_2D_SGIS.
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 number of color components in the tex‐
ture. Must be 1, 2, 3, or 4, or one of the following
symbolic constants: GL_ALPHA, GL_ALPHA4, GL_ALPHA8,
GL_ALPHA12, GL_ALPHA16, GL_LUMINANCE, GL_LUMINANCE4,
GL_LUMINANCE8, GL_LUMINANCE12, GL_LUMINANCE16, GL_LUMI‐
NANCE_ALPHA, GL_LUMINANCE4_ALPHA4, GL_LUMI‐
NANCE6_ALPHA2, GL_LUMINANCE8_ALPHA8, GL_LUMI‐
NANCE12_ALPHA4, GL_LUMINANCE12_ALPHA12, GL_LUMI‐
NANCE16_ALPHA16, GL_INTENSITY, GL_INTENSITY4, GL_INTEN‐
SITY8, GL_INTENSITY12, GL_INTENSITY16, GL_R3_G3_B2,
GL_RGB, GL_RGB4, GL_RGB5, GL_RGB8, GL_RGB10, GL_RGB12,
GL_RGB16, GL_RGBA, GL_RGBA2, GL_RGBA4, GL_RGB5_A1,
GL_RGBA8, GL_RGB10_A2, GL_RGBA12, GL_RGBA16, GL_COM‐
PRESSED_ALPHA, GL_COMPRESSED_LUMINANCE, GL_COM‐
PRESSED_LUMINANCE_ALPHA, GL_COMPRESSED_INTENSITY,
GL_COMPRESSED_RGB, GL_COMPRESSED_RGBA.
width Specifies the width of the texture image. Must be
2^n+2(border) for some integer n. All implementations
support texture images that are at least 64 texels
wide.
height Specifies the height of the texture image. Must be
2^m+2(border) for some integer m. All implementations
support texture images that are at least 64 texels
high.
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_LUMI‐
NANCE, and GL_LUMINANCE_ALPHA.
type Specifies the data type of the pixel data. The follow‐
ing 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 graphi‐
cal primitive for which texturing is enabled. To enable and disable
two-dimensional texturing, call glEnable and glDisable with argument
GL_TEXTURE_2D.
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; they are identical to the pixel formats
used for glDrawPixels.
If target is GL_PROXY_TEXTURE_2D, no data is read from pixels, but all
of the texture image state is recalculated, checked for consistency,
and checked against the implementation's capabilities. If the implemen‐
tation cannot handle a texture of the requested texture size, it sets
all of the image state to 0, but does not generate an error (see
glGetError). To query for an entire mipmap array, use an image array
level greater than or equal to 1.Proxy texture can also be used to
query if the format/internalformat/type combination will result in con‐
stant texture.
If target is GL_TEXTURE_2D, data is read from pixels as a sequence of
signed or unsigned bytes, shorts, or longs, or single-precision float‐
ing-point values, depending on type. These values are grouped into
sets of one, two, three, or four values, depending on format, to form
elements. 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).
The first element corresponds to the lower left corner of the texture
image. Subsequent elements progress left-to-right through the remain‐
ing texels in the lowest row of the texture image, and then in succes‐
sively 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 pixels. It can
assume one of nine symbolic values:
GL_COLOR_INDEX
Each element is a single value, a color index. The GL con‐
verts it 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. The GL converts it
to floating point and assembles it into an RGBA element by
attaching 0 for green and blue, and 1 for alpha. Each compo‐
nent 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. The GL converts it
to floating point and assembles it into an RGBA element by
attaching 0 for red and blue, and 1 for alpha. Each compo‐
nent 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. The GL converts it
to floating point and assembles it into an RGBA element by
attaching 0 for red and green, and 1 for alpha. Each compo‐
nent 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. 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
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. The GL converts it to float‐
ing point and assembles it into an RGBA element by attaching
1 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. 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
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. 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 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).
Refer to the glDrawPixels reference page for a description of the
acceptable values for the type parameter.
If an application wants to store the texture at a certain resolution or
in a certain format, it can request the resolution and format with
internalformat. The GL will choose an internal representation that
closely approximates that requested by internalformat, but it may not
match exactly. (The representations specified by GL_LUMINANCE,
GL_LUMINANCE_ALPHA, GL_RGB, and GL_RGBA must match exactly. The numeric
values 1, 2, 3, and 4 may also be used to specify the above representa‐
tions.)
Use the GL_PROXY_TEXTURE_2D target to try out a resolution and format.
The implementation will update and recompute its best match for the
requested storage resolution and format. To then query this state, call
glGetTexLevelParameter. If the texture cannot be accommodated, texture
state is set to 0.
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 glDrawPix‐
els.
glTexImage2D and GL_PROXY_TEXTURE_2D are only available if the GL ver‐
sion is 1.1 or greater.
Internal formats other than 1, 2, 3, or 4 may only be used if the GL
version is 1.1 or greater.
In GL version 1.1 or greater, pixels 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 initial‐
ize this texture memory. The image is undefined if the user tries to
apply an uninitialized portion of the texture image to a primitive.
If GL_UNPACK_CONSTANT_DATA_SUNX(see glPixelStore) is set to GL_TRUE and
all other unpack pixel store values are default, then the pixels
pointer may be used internally without the library making a second
copy. Note that whether an application specified constant texture is
used as-is internally is implementation dependent, an implementation
may still make a second copy if necessary. It is the application's
responsibility to make sure that the format/internal format combination
is meaningful when constant data is used. For example, if the format is
GL_ABGR_EXT and the internalformat is GL_LUMINANCE, then the pixels
sent down as constant data should have the same value in the R, G and B
channels and a 1 for alpha. Note that GL_UNPACK_CONSTANT_DATA_SUNX is
ignored if pixel transfer is enabled.
If GL_UNPACK_CONSTANT_DATA_SUNX is set to GL_TRUE and application wants
to change part of the texture image that has been sent down, the appli‐
cation should first call glFinishTextureSUNX before a part or all of
this texture image is changed.
If a texture image is defined as constant during display list creation,
then the contents of the texture image should remain unchanged for the
life of the display list. Changing this constant texture image will
result in unpredictable results.
ERRORS
GL_INVALID_ENUM is generated if target is not GL_TEXTURE_2D or
GL_PROXY_TEXTURE_2D.
GL_INVALID_ENUM is generated if format is not an accepted format con‐
stant. Format constants other than GL_STENCIL_INDEX and GL_DEPTH_COM‐
PONENT are accepted.
GL_INVALID_ENUM is generated if 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 0.
GL_INVALID_VALUE may be generated if level is greater than log2max,
where max is the returned value of GL_MAX_TEXTURE_SIZE.
GL_INVALID_VALUE is generated if internalformat is not 1, 2, 3, 4, or
one of the accepted resolution and format symbolic constants.
GL_INVALID_VALUE is generated if width or height is less than 0 or
greater than 2 + GL_MAX_TEXTURE_SIZE, or if either cannot be repre‐
sented 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.
GL_INVALID_VALUE is generated if target is GL_DETAIL_TEXTURE_2D_SGIS
and level or border is not 0.
ASSOCIATED GETS
glGetTexImage
glIsEnabled with argument GL_TEXTURE_2D
SEE ALSO
glCopyPixels, glCopyTexImage1D, glCopyTexImage2D, glCopyTexSubImage1D,
glCopyTexSubImage2D, glDrawPixels, glPixelStore, glPixelTransfer,
glTexEnv, glTexGen, glTexImage1D, glTexSubImage1D, glTexSubImage2D,
glTexParameter, glFinishTextureSUNX, glGetTexLevelParameter
15 Mar 97 GLTEXIMAGE2D(3gl)
