glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
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 GLTEXTURE2D,
GLPROXYTEXTURE2D, GLPROXYTEXTURE2DEXT, or
GLDETAILTEXTURE2DSGIS.
level Specifies the level-of-detail number. Level 0 is the base
image level. Level n is the nth mipmap reduction image.
components is used to request the internal storage format of the texture
image. It must be 1, 2, 3, or 4, or one of the following
symbolic constants: GLALPHA, GLALPHA4, GLALPHA4EXT,
GLALPHA8, GLALPHA8EXT, GLALPHA12, GLALPHA12EXT,
GLALPHA16, GLALPHA16EXT, GLLUMINANCE, GLLUMINANCE4,
GLLUMINANCE4EXT, GLLUMINANCE8, GLLUMINANCE8EXT,
GLLUMINANCE12, GLLUMINANCE12EXT, GLLUMINANCE16,
GLLUMINANCE16EXT, GLLUMINANCEALPHA, GLLUMINANCE4ALPHA4,
GLLUMINANCE4ALPHA4EXT, GLLUMINANCE6ALPHA2,
GLLUMINANCE6ALPHA2EXT, GLLUMINANCE8ALPHA8,
GLLUMINANCE8ALPHA8EXT, GLLUMINANCE12ALPHA4,
GLLUMINANCE12ALPHA4EXT, GLLUMINANCE12ALPHA12,
GLLUMINANCE12ALPHA12EXT, GLLUMINANCE16ALPHA16,
GLLUMINANCE16ALPHA16EXT, GLINTENSITY, GLINTENSITYEXT,
GLINTENSITY4, GLINTENSITY4EXT, GLINTENSITY8,
GLINTENSITY8EXT, GLINTENSITY12, GLINTENSITY12EXT,
GLINTENSITY16, GLINTENSITY16EXT, GLRGB, GLR3G3B2,
GLRGB2EXT, GLRGB4, GLRGB4EXT, GLRGB5, GLRGB5EXT,
GLRGB8, GLRGB8EXT, GLRGB10, GLRGB10EXT, GLRGB12,
GLRGB12EXT, GLRGB16, GLRGB16EXT, GLRGBA, GLRGBA2,
GLRGBA2EXT, GLRGBA4, GLRGBA4EXT, GLRGB5A1,
GLRGB5A1EXT, GLRGBA8, GLRGB10A2, GLRGB10A2EXT,
GLRGBA12, GLRGBA12EXT, GLRGBA16, GLRGBA16EXT,
GLDEPTHCOMPONENT, GLDEPTHCOMPONENT16SGIX,
GLDEPTHCOMPONENT24SGIX, GLDEPTHCOMPONENT32SGIX,
GLDUALALPHA4SGIS, GLDUALALPHA8SGIS,
GLDUALALPHA12SGIS, GLDUALALPHA16SGIS,
GLDUALLUMINANCE4SGIS, GLDUALLUMINANCE8SGIS,
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
GLDUALLUMINANCE12SGIS, GLDUALLUMINANCE16SGIS,
GLDUALINTENSITY4SGIS, GLDUALINTENSITY8SGIS,
GLDUALINTENSITY12SGIS, GLDUALINTENSITY16SGIS,
GLDUALLUMINANCEALPHA4SGIS, GLDUALLUMINANCEALPHA8SGIS,
GLQUADALPHA4SGIS, GLQUADALPHA8SGIS,
GLQUADLUMINANCE4SGIS, GLQUADLUMINANCE8SGIS,
GLQUADINTENSITY4SGIS, or GLQUADINTENSITY8SGIS.
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
2**m+I*border for some integer m, where I is 2 when
GLINTERLACESGIX is disabled, and 1 otherwise.
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: GLCOLORINDEX, GLRED,
GLGREEN, GLBLUE, GLALPHA, GLRGB, GLRGBA, GLABGREXT,
GLLUMINANCE, GLLUMINANCEALPHA, and GLDEPTHCOMPONENT.
type Specifies the data type of the pixel data. The following
symbolic values are accepted: GLUNSIGNEDBYTE, GLBYTE,
GLBITMAP, GLUNSIGNEDSHORT, GLSHORT, GLUNSIGNEDINT,
GLINT, GLFLOAT, GLUNSIGNEDBYTE332EXT,
GLUNSIGNEDSHORT4444EXT, GLUNSIGNEDSHORT5551EXT,
GLUNSIGNEDINT8888EXT, and
GLUNSIGNEDINT1010102EXT.
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
GLTEXTURE2D.
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 the internal
resolution and format used to store the image. The last three arguments
describe the way the image is represented in memory, and they are
identical to the pixel formats used for glDrawPixels.
If target is GLPROXYTEXTURE2D or GLPROXYTEXTURE2DEXT 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 implementation cannot handle a texture of the
requested texture size, it will set all of the texture image state to 0
(GLTEXTUREWIDTH, GLTEXTUREHEIGHT, GLTEXTUREBORDER,
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
GLTEXTUREINTERNALFORMAT, GLTEXTURECOMPONENTS, GLTEXTUREREDSIZE,
GLTEXTUREREDSIZEEXT, GLTEXTUREGREENSIZE,
GLTEXTUREGREENSIZEEXT, GLTEXTUREBLUESIZE,
GLTEXTUREBLUESIZEEXT, GLTEXTUREALPHASIZE,
GLTEXTUREALPHASIZEEXT, GLTEXTURELUMINANCESIZE,
GLTEXTURELUMINANCESIZEEXT, GLTEXTUREINTENSITYSIZE), and
GLTEXTUREINTENSITYSIZEEXT), but no error will be generated.
If target is GLTEXTURE2D or GLDETAILTEXTURE2DSGIS, 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 elements. (Note that if type is set to
GLUNSIGNEDBYTE332EXT, GLUNSIGNEDSHORT4444EXT,
GLUNSIGNEDSHORT5551EXT, GLUNSIGNEDINT8888EXT, or
GLUNSIGNEDINT1010102EXT then it is a special case in which all the
elements of each group are packed into a single unsigned byte, unsigned
short, or unsigned int. This is described in glDrawPixels.)
If type is GLBITMAP, the data is considered as a string of unsigned
bytes (and format must be GLCOLORINDEX). Each data byte is treated as
eight 1-bit elements, with bit ordering determined by GLUNPACKLSBFIRST
(see glPixelStore).
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.
When GLINTERLACESGIX is enabled, only rows (0,2,4,...) of the texture
image (where the border is considered part of the texture image) are
defined. Rows (1,3,5,...) are left undefined and can only be defined
using glTexSubImage2D, glTexSubImage2DEXT, glCopyTexSubImage2D or
glCopyTexSubImage2DEXT.
Note, that when GLINTERLACESGIX is enabled the total height (i.e., the
height of interior texture image plus twice the border) of the defined
texture is 2*height.
Each element of pixels is converted to an RGBA element according to
format, as detailed below. Except for GLCOLORINDEX, after the
conversion to RGBA, each component is multiplied by the signed scale
factor GLcSCALE, added to the signed bias GLcBIAS, and clamped to the
range [0,1], where c is RED, GREEN, BLUE, or ALPHA, respectively (see
glPixelTransfer).
According to format, the conversion to RGBA is as follows:
GLCOLORINDEX
Each element is a single value, a color index. It is converted
to fixed point (with an unspecified number of zero bits to the
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
right of the binary point), shifted left or right depending on
the value and sign of GLINDEXSHIFT, and added to
GLINDEXOFFSET (see glPixelTransfer). The resulting index is
converted to a set of color components using the
GLPIXELMAPITOR, GLPIXELMAPITOG, GLPIXELMAPITOB,
and GLPIXELMAPITOA tables, and clamped to the range [0,1].
GLRED 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.
GLGREEN 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.
GLBLUE 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.
GLALPHA 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.
GLRGB Each element is an RGB triple: first red, then green, and then
blue. It is converted to floating point and assembled into an
RGBA element by attaching 1.0 for alpha.
GLRGBA,
GLABGREXT
Each element contains all four components; for GLRGBA, the red
component is first, followed by green, then blue, and then
alpha; for GLABGREXT the order is alpha, blue, green, and
then red.
GLLUMINANCE
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.
GLLUMINANCEALPHA
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.
Please refer to the glDrawPixels reference page for a description of the
acceptable values for the type parameter.
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
An application may desire that the texture be stored at a certain
resolution, or that it be stored in a certain format. This resolution and
format can be requested by components. The GL will choose an internal
representation that closely approximates that requested by components,
but it may not match exactly. (The representations specified by
GLLUMINANCE, GLLUMINANCEALPHA, GLRGB, and GLRGBA must match exactly.
The numeric values 1, 2, 3, and 4 may also be used to specify the above
representations.)
The GLPROXYTEXTURE2D or GLPROXYTEXTURE2DEXT target can be used to
try out a particular resolution and format. The implementation will
compute its best match for the requested storage resolution and format.
This state can then be queried using glGetTexLevelParameter. If the
texture cannot be accomodated texture state will be 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.
The mapping of components from the canonical RGBA to the internal storage
formats that begin with GLDUAL and GLQUAD needs to be clarified.
There are three cases. The first case is for the GLDUAL formats that
are groups of GLALPHA, GLLUMINANCE, and GLINTENSITY. The R value goes
to the first group while the A value goes to the second group. The
second case is for the GLDUAL formats that are groups of
GLLUMINANCEALPHA. The R and G values go to the first group while the B
and A values go to the second group. The third case is for the GLQUAD
formats. The R value goes to the first group, the G value to the second
group, the B value to the third group, and the A value to the fourth
group.
When components is set to GLDEPTHCOMPONENT, GLDEPTHCOMPONENT16SGIX,
GLDEPTHCOMPONENT24SGIX, or GLDEPTHCOMPONENT32SGIX, and format has
the value GLDEPTHCOMPONENT, glTexImage2D defines a depth texture that
can be used for shadow mapping. See glIntro and glTexParameter for more
information.
NOTES
Texturing has no effect in color index mode.
glPixelStore and glPixelTransfer modes affect texture images in exactly
the way they affect glDrawPixels. glTexImage2D and GLPROXYTEXTURE2D
are only available if the GL version 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 initialize this
texture memory. The image is undefined if the user tries to apply an
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
uninitialized portion of the texture image to a primitive.
abgr is supported only when the extensions string contains GLEXTabgr.
If type is set to GLUNSIGNEDBYTE332EXT,
GLUNSIGNEDSHORT4444EXT, GLUNSIGNEDSHORT5551EXT,
GLUNSIGNEDINT8888EXT, or GLUNSIGNEDINT1010102EXT and the
EXTpackedpixels extension is not supported then a GLINVALIDENUM error
is generated.
See glIntro for more information on using extensions.
ERRORS
GLINVALIDENUM is generated when target is not one of the allowable
values.
GLINVALIDENUM is generated when format is not an accepted format.
GLINVALIDENUM is generated when type is not an accepted type.
GLINVALIDENUM is generated if type is GLBITMAP and format is not
GLCOLORINDEX.
GLINVALIDVALUE is generated if level is less than zero
GLINVALIDVALUE is generated if components is not 1, 2, 3, or 4 or one
of the accepted symbolic constants.
GLINVALIDVALUE is generated if width or height is less than zero,
greater than 2+GLMAXTEXTURESIZE, when width cannot be represented as
2**k+2*border for some integer k, or when height cannot be represented as
2**k+I*border, where I is 2 when GLINTERLACESGIX is disabled and 1
otherwise.
GLINVALIDVALUE is generated if border is not 0 or 1.
GLINVALIDOPERATION is generated if glTexImage2D is executed between the
execution of glBegin and the corresponding execution of glEnd.
GLINVALIDVALUE is generated if the implementation cannot accomodate a
texture of the requested size.
GLINVALIDVALUE is generated if target is GLDETAILTEXTURE2DSGIS and
level is not zero.
GLINVALIDVALUE is generated if target is GLDETAILTEXTURE2DSGIS and
border is not zero.
ASSOCIATED GETS
glGetTexImage
glIsEnabled with argument GLTEXTURE2D
glGetTexLevelParameter with a first argument of GLPROXYTEXTURE2D or
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
GLPROXYTEXTURE2DEXT and a third argument of GLTEXTUREREDSIZE,
GLTEXTUREREDSIZEEXT, GLTEXTUREGREENSIZE,
GLTEXTUREGREENSIZEEXT, GLTEXTUREBLUESIZE,
GLTEXTUREBLUESIZEEXT, GLTEXTUREALPHASIZE,
GLTEXTUREALPHASIZEEXT, GLTEXTURELUMINANCESIZE,
GLTEXTURELUMINANCESIZEEXT, GLTEXTUREINTENSITYSIZE,
GLTEXTUREINTENSITYSIZEEXT, GLTEXTUREWIDTH, GLTEXTUREHEIGHT,
GLTEXTUREBORDER, GLTEXTUREINTERNALFORMAT, or GLTEXTURECOMPONENTS.
MACHINE DEPENDENCIES
RealityEngine, RealityEngine2, and VTX systems do not support color
matrix transformations on images as they are loaded to or read back from
texture memory.
RealityEngine, RealityEngine2, and VTX systems do not support convolving
images as they are loaded into texture memory.
On RealityEngine, RealityEngine2, and VTX systems the width and height of
a detail texture must both be 256. On High Impact and Maximum Impact
systems, detail texture size must be 128x128 or 256x256.
Detail texturing acts as if the mipmap stack were extended by a number of
levels equal to the absolute value of the GLDETAILTEXTURELEVELSGIS
parameter. The number of normal mipmap levels plus the number of detail
levels must not exceed the maximum number of levels that can be supported
on the hardware. For example, on InfiniteReality systems the maximum
number of levels is 15. A detail texture at level -4 could be supported
on a base texture of size 2K (that is, a base texture with 11 levels) but
not on a base texture that is larger than 2K (one with 12 or more
levels). Failure to observe this constraint causes detail textures to
swim or jitter.
RealityEngine, RealityEngine2, and VTX systems do not support histogram
or minmax operations on images as they are being loaded into texture
memory.
The SGIXinterlace extension is supported only on InfiniteReality
systems, on RealityEngine, RealityEngine2, and VTX systems, and on O2
systems.
The EXTpackedpixels extension is not supported on RealityEngine,
RealityEngine2, and VTX systems.
On RealityEngine, RealityEngine2, and VTX systems:
1. The texture environment must be defined and texturing must be
enabled before loading a texture.
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
2. Texture formats composed only of alpha are not supported.
3. Borders are not supported; hence the border width must be 0.
4. Proxy textures are not supported.
5. glTexImage2D with a NULL texture image may not be used inside a
display list.
6. GLINTERLACESGIX is not supported (see glEnable).
On High Impact and Maximum Impact systems the number of bits per
component, represented internally, is the same for all components and
will be 4, 8, or 12 bits per component. All specified internal formats
will receive an equal or greater representation in this scheme, up to the
12-bit limit. High Impact and Maximum Impact on Indigo2 systems do not
support texture internal formats of the type GLINTENSITY or GLALPHA,
although High Impact and Maximum Impact on Octane systems do support
these types.
High Impact and Maximum Impact on Indigo2 systems without the TRAM option
card support 4 bits per component for GLRGB and GLRGBA, 4/8 bits per
component for GLLUMINANCEALPHA, and 4/8/12 bits per component for
GLLUMINANCE.
Texture borders are not supported on InfiniteReality systems, so the
border width should always be zero. Applications should use the texture
wrap mode GLCLAMPTOEDGESGIS to obtain behavior similar to that of
borders.
The SGIStextureselect extension is supported only on InfiniteReality
systems, High Impact and Maximum Impact on Octane systems, and High
Impact and Maximum Impact on Indigo2 systems with the TRAM option card.
On InfiniteReality, RealityEngine, RealityEngine2, and VTX systems, and
High Impact and Maximum Impact systems, texture objects (see
glBindTextureEXT) are significantly faster than display-listed textures,
and therefore are recommended for managing texture memory.
SEE ALSO
glConvolutionFilter2DEXT, glDetailTexFuncSGIS, glDrawPixels, glFog,
glEnable, glHistogramEXT, glMinmaxEXT, glPixelStore, glPixelTransfer,
glSeparableFilter2DEXT, glTexEnv, glTexGen, glTexImage1D, glTexParameter.
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