glteximage2d - Man Page
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 GL_TEXTURE_2D,
GL_PROXY_TEXTURE_2D_EXT, 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.
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: GL_ALPHA, GL_ALPHA4_EXT, GL_ALPHA8_EXT,
GL_ALPHA12_EXT, GL_ALPHA16_EXT, GL_LUMINANCE,
GL_LUMINANCE4_EXT, GL_LUMINANCE8_EXT, GL_LUMINANCE12_EXT,
GL_LUMINANCE16_EXT, GL_LUMINANCE_ALPHA,
GL_LUMINANCE4_ALPHA4_EXT, GL_LUMINANCE6_ALPHA2_EXT,
GL_LUMINANCE8_ALPHA8_EXT, GL_LUMINANCE12_ALPHA4_EXT,
GL_LUMINANCE12_ALPHA12_EXT, GL_LUMINANCE16_ALPHA16_EXT,
GL_INTENSITY_EXT, GL_INTENSITY4_EXT, GL_INTENSITY8_EXT,
GL_INTENSITY12_EXT, GL_INTENSITY16_EXT, GL_RGB, GL_RGB2_EXT,
GL_RGB4_EXT, GL_RGB5_EXT, GL_RGB8_EXT, GL_RGB10_EXT,
GL_RGB12_EXT, GL_RGB16_EXT, GL_RGBA, GL_RGBA2_EXT,
GL_RGBA4_EXT, GL_RGB5_A1_EXT, GL_RGBA8_EXT, GL_RGB10_A2_EXT,
GL_RGBA12_EXT, GL_RGBA16_EXT, GL_DEPTH_COMPONENT,
GL_DUAL_ALPHA4_SGIS, GL_DUAL_ALPHA8_SGIS,
GL_DUAL_ALPHA12_SGIS, GL_DUAL_ALPHA16_SGIS,
GL_DUAL_LUMINANCE4_SGIS, GL_DUAL_LUMINANCE8_SGIS,
GL_DUAL_LUMINANCE12_SGIS, GL_DUAL_LUMINANCE16_SGIS,
GL_DUAL_INTENSITY4_SGIS, GL_DUAL_INTENSITY8_SGIS,
GL_DUAL_INTENSITY12_SGIS, GL_DUAL_INTENSITY16_SGIS,
GL_DUAL_LUMINANCE_ALPHA4_SGIS, GL_DUAL_LUMINANCE_ALPHA8_SGIS,
GL_QUAD_ALPHA4_SGIS, GL_QUAD_ALPHA8_SGIS,
GL_QUAD_LUMINANCE4_SGIS, GL_QUAD_LUMINANCE8_SGIS,
GL_QUAD_INTENSITY4_SGIS, or GL_QUAD_INTENSITY8_SGIS.
width Specifies the width of the texture image. Must be
2**n+2*border for some integer n.
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
height Specifies the height of the texture image. Must
2**m+I*border for some integer m, where I is 2 when
GL_INTERLACE_SGIX 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: GL_COLOR_INDEX, GL_RED,
GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_RGBA, GL_ABGR_EXT,
GL_LUMINANCE, GL_LUMINANCE_ALPHA, and GL_DEPTH_COMPONENT.
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, GL_FLOAT, GL_UNSIGNED_BYTE_3_3_2_EXT,
GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT,
GL_UNSIGNED_INT_8_8_8_8_EXT, and
GL_UNSIGNED_INT_10_10_10_2_EXT.
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 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 GL_PROXY_TEXTURE_2D_EXT 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 (GL_TEXTURE_WIDTH,
GL_TEXTURE_HEIGHT, GL_TEXTURE_BORDER, GL_TEXTURE_COMPONENTS,
GL_TEXTURE_RED_SIZE_EXT, GL_TEXTURE_GREEN_SIZE_EXT,
GL_TEXTURE_BLUE_SIZE_EXT, GL_TEXTURE_ALPHA_SIZE_EXT,
GL_TEXTURE_LUMINANCE_SIZE_EXT, and GL_TEXTURE_INTENSITY_SIZE_EXT), but no
error will be generated.
If target is GL_TEXTURE_2D or GL_DETAIL_TEXTURE_2D_SGIS, 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
GL_UNSIGNED_BYTE_3_3_2_EXT, GL_UNSIGNED_SHORT_4_4_4_4_EXT,
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
GL_UNSIGNED_SHORT_5_5_5_1_EXT, GL_UNSIGNED_INT_8_8_8_8_EXT, or
GL_UNSIGNED_INT_10_10_10_2_EXT 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 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 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 GL_INTERLACE_SGIX 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 glTexSubImage2DEXT or glCopyTexSubImage2DEXT. Note, that when
GL_INTERLACE_SGIX 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 GL_COLOR_INDEX, after the
conversion to RGBA, 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], where c is RED, GREEN, BLUE, or ALPHA, respectively (see
glPixelTransfer).
According to format, the conversion to RGBA is as follows:
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.
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.
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
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.
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.
GL_RGB 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.
GL_RGBA,
GL_ABGR_EXT
Each element contains all four components; for GL_RGBA, the red
component is first, followed by green, then blue, and then
alpha; for GL_ABGR_EXT the order is alpha, blue, green, and
then red.
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.
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.
Please refer to the glDrawPixels reference page for a description of the
acceptable values for the type parameter.
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
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
representations.)
The GL_PROXY_TEXTURE_2D_EXT 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.
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
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 GL_DUAL_ and GL_QUAD_ needs to be clarified.
There are three cases. The first case is for the GL_DUAL_ formats that
are groups of GL_ALPHA, GL_LUMINANCE, and GL_INTENSITY. The R value goes
to the first group while the A value goes to the second group. The
second case is for the GL_DUAL_ formats that are groups of
GL_LUMINANCE_ALPHA. 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 GL_QUAD_
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 and format have the value GL_DEPTH_COMPONENT,
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.
The proxy textures and the internal format components symbolic values are
part of the EXT_texture extension, not part of the core GL command set.
If GL_EXT_texture is included in the string returned by glGetString, when
called with argument GL_EXTENSIONS, extension EXT_texture is supported by
the GL. Similarly, abgr is supported only when the extensions string
contains GL_EXT_abgr.
If type is set to GL_UNSIGNED_BYTE_3_3_2_EXT,
GL_UNSIGNED_SHORT_4_4_4_4_EXT, GL_UNSIGNED_SHORT_5_5_5_1_EXT,
GL_UNSIGNED_INT_8_8_8_8_EXT, or GL_UNSIGNED_INT_10_10_10_2_EXT and the
EXT_packed_pixels extension is not supported then a GL_INVALID_ENUM error
is generated.
See glIntro for more information on using extensions.
ERRORS
GL_INVALID_ENUM is generated when target is not one of the allowable
values.
GL_INVALID_ENUM is generated when format is not an accepted format.
GL_INVALID_ENUM is generated when type is not an accepted type.
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
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
GL_INVALID_VALUE is generated if components is not 1, 2, 3, or 4 or one
of the accepted symbolic constants.
GL_INVALID_VALUE is generated if width or height is less than zero,
greater than 2+GL_MAX_TEXTURE_SIZE, 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 GL_INTERLACE_SGIX is disabled and 1
otherwise.
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_TEXTURE_TOO_LARGE_EXT is generated if the implementation cannot
accomodate a texture of the requested size.
GL_INVALID_VALUE is generated if target is GL_DETAIL_TEXTURE_2D_SGIS and
level is not zero.
GL_INVALID_VALUE is generated if target is GL_DETAIL_TEXTURE_2D_SGIS and
border is not zero.
ASSOCIATED GETS
glGetTexImage
glIsEnabled with argument GL_TEXTURE_2D
glGetTexLevelParameter with a first argument of GL_PROXY_TEXTURE_2D_EXT
and a third argument of GL_TEXTURE_RED_SIZE_EXT,
GL_TEXTURE_GREEN_SIZE_EXT, GL_TEXTURE_BLUE_SIZE_EXT,
GL_TEXTURE_ALPHA_SIZE_EXT, GL_TEXTURE_LUMINANCE_SIZE_EXT,
GL_TEXTURE_INTENSITY_SIZE_EXT, GL_TEXTURE_WIDTH, GL_TEXTURE_HEIGHT,
GL_TEXTURE_BORDER, or GL_TEXTURE_COMPONENTS.
MACHINE DEPENDENCIES
RealityEngine, RealityEngine2, and VTX systems do not support convolving
images as they are loaded into texture memory.
InfiniteReality systems have limited support for convolving images as
they are loaded into texture memory. The image resulting from
convolution must be a multiple of 8 in width.
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.
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
RealityEngine, RealityEngine2, and VTX systems do not support histogram
or minmax operations on images as they are being loaded into texture
memory.
The SGIX_interlace extension is supported only on InfiniteReality systems
and on RealityEngine, RealityEngine2, and VTX systems.
The EXT_packed_pixels extension is not supported on RealityEngine,
RealityEngine2, and VTX systems; it will be supported on High Impact and
Maximum Impact systems in a future release.
GL_DEPTH_COMPONENT textures are a partial implementation of an extension
that will be more fully documented in a subsequent release. They are
supported only on InfiniteReality systems.
On RealityEngine, RealityEngine2, and VTX systems:
1. The texture environment must be defined and texturing must be
enabled before loading a texture.
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. GL_INTERLACE_SGIX is not supported (see glEnable).
High Impact and Maximum Impact systems do not support texture internal
formats of the type GL_INTENSITY or GL_ALPHA. Internally the number of
bits per component 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 systems without the TRAM option card
support 4 bits per component for GL_RGB and GL_RGBA, 4/8 bits per
component for GL_LUMINANCE_ALPHA, and 4/8/12 bits per component for
GL_RGBA.
On InfiniteReality systems, defining 2D and 3D textures in arbitrary
order can cause incorrect results if texture memory is overcommitted.
Workarounds are to define all 3D textures before defining any 2D
textures, or to ensure that the application never defines more textures
than will fit in texture memory. This will be fixed in the next release.
Texture borders are not supported on InfiniteReality systems, so the
border width should always be zero. Borders will be supported in future
releases. However, borders use texture memory very inefficiently; up to
four times the memory required by the base texture may be needed to
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glTexImage2D(3G) OpenGL Reference glTexImage2D(3G)
support borders properly. Whenever possible, applications should use the
texture wrap mode GL_CLAMP_TO_EDGE_SGIS and borderless textures. This
might be essential for large textures, which otherwise won't fit in
texture memory because of the border overhead.
The SGIS_texture_select extension is supported only on InfiniteReality
systems and on High Impact and Maximum Impact systems with the TRAM
option card.
SEE ALSO
glConvolutionFilter2DEXT, glDetailTexFuncSGIS, glDrawPixels, glFog,
glEnable, glHistogramEXT, glMinmaxEXT, glPixelStore, glPixelTransfer,
glSeparableFilter2DEXT, glTexEnv, glTexGen, glTexImage1D, glTexParameter.
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