_C_ License Applicability. Except to the extent portions of this file are
_C_ made subject to an alternative license as permitted in the SGI Free
_C_ Software License B, Version 1.1 (the "License"), the contents of this
_C_ file are subject only to the provisions of the License. You may not use
_C_ this file except in compliance with the License. You may obtain a copy
_C_ of the License at Silicon Graphics, Inc., attn: Legal Services, 1600
_C_ Amphitheatre Parkway, Mountain View, CA 94043-1351, or at:
_C_ 
_C_ http://oss.sgi.com/projects/FreeB
_C_ 
_C_ Note that, as provided in the License, the Software is distributed on an
_C_ "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS
_C_ DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND
_C_ CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A
_C_ PARTICULAR PURPOSE, AND NON-INFRINGEMENT.
_C_ 
_C_ Original Code. The Original Code is: OpenGL Sample Implementation,
_C_ Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
_C_ Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
_C_ Copyright in any portions created by third parties is as indicated
_C_ elsewhere herein. All Rights Reserved.
_C_ 
_C_ Additional Notice Provisions: The application programming interfaces
_C_ established by SGI in conjunction with the Original Code are The
_C_ OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
_C_ April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
_C_ 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
_C_ Window System(R) (Version 1.3), released October 19, 1998. This software
_C_ was created using the OpenGL(R) version 1.2.1 Sample Implementation
_C_ published by SGI, but has not been independently verified as being
_C_ compliant with the OpenGL(R) version 1.2.1 Specification.
_C_
_C_ The first character in this file must be an '_'!
_C_ Anything on a line after _C_ is ignored
_define(_filters,eqn)_C_
_C_      eqn is automatically replaced with neqn for nroff
_header(TexImage2D,specify a two-dimensional texture image)
_names(TexImage2D)
.EQ
delim $$
.EN
.SH PARAMETERS
_phead(_param1)
Specifies the target texture.
Must be _const(TEXTURE_2D) or _const(PROXY_TEXTURE_2D).
_phead(_param2)
Specifies the level-of-detail number.
Level 0 is the base image level.
Level \f2n\fP is the \f2n\fPth mipmap reduction image.
_phead(_param3)
Specifies the number of color components in the texture.
Must be 1, 2, 3, or 4, or one of the following symbolic constants:
_const(ALPHA),
_const(ALPHA4),
_const(ALPHA8),
_const(ALPHA12),
_const(ALPHA16),
_const(LUMINANCE),
_const(LUMINANCE4),
_const(LUMINANCE8),
_const(LUMINANCE12),
_const(LUMINANCE16),
_const(LUMINANCE_ALPHA),
_const(LUMINANCE4_ALPHA4),
_const(LUMINANCE6_ALPHA2),
_const(LUMINANCE8_ALPHA8),
_const(LUMINANCE12_ALPHA4),
_const(LUMINANCE12_ALPHA12),
_const(LUMINANCE16_ALPHA16),
_const(INTENSITY),
_const(INTENSITY4),
_const(INTENSITY8),
_const(INTENSITY12),
_const(INTENSITY16),
_const(R3_G3_B2),
_const(RGB),
_const(RGB4),
_const(RGB5),
_const(RGB8),
_const(RGB10),
_const(RGB12),
_const(RGB16),
_const(RGBA),
_const(RGBA2),
_const(RGBA4),
_const(RGB5_A1),
_const(RGBA8),
_const(RGB10_A2),
_const(RGBA12), or
_const(RGBA16).
_phead(_param4)
Specifies the width of the texture image.
Must be $2 sup n ~+~ 2 ( _eqnparam6 )$ for some integer $n$. All
implementations support texture images that are at least 64 texels
wide.
_phead(_param5)
Specifies the height of the texture image.
Must be $2 sup m ~+~ 2 ( _eqnparam6 )$ for some integer $m$. All
implementations support texture images that are at least 64 texels
high.
_phead(_param6)
Specifies the width of the border.
Must be either 0 or 1.
_phead(_param7)
Specifies the format of the pixel data.
The following symbolic values are accepted:
_const(COLOR_INDEX),
_const(RED),
_const(GREEN),
_const(BLUE),
_const(ALPHA),
_const(RGB),
_const(BGR)
_const(RGBA),
_const(BGRA),
_C_ _const(ABGR_EXT),
_const(LUMINANCE), and
_const(LUMINANCE_ALPHA).
_phead(_param8)
Specifies the data type of the pixel data.
The following symbolic values are accepted:
_const(UNSIGNED_BYTE),
_const(BYTE),
_const(BITMAP),
_const(UNSIGNED_SHORT),
_const(SHORT),
_const(UNSIGNED_INT),
_const(INT),
_const(FLOAT),
_const(UNSIGNED_BYTE_3_3_2),
_const(UNSIGNED_BYTE_2_3_3_REV),
_const(UNSIGNED_SHORT_5_6_5),
_const(UNSIGNED_SHORT_5_6_5_REV),
_const(UNSIGNED_SHORT_4_4_4_4),
_const(UNSIGNED_SHORT_4_4_4_4_REV),
_const(UNSIGNED_SHORT_5_5_5_1),
_const(UNSIGNED_SHORT_1_5_5_5_REV),
_const(UNSIGNED_INT_8_8_8_8),
_const(UNSIGNED_INT_8_8_8_8_REV),
_const(UNSIGNED_INT_10_10_10_2), and
_const(UNSIGNED_INT_2_10_10_10_REV).
_phead(_param9)
Specifies a pointer to the image data in memory.
.SH DESCRIPTION
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 _cmnd(Enable)
and _cmnd(Disable) with argument _const(TEXTURE_2D).
.P
To define texture images, call _cmnd. 
The arguments describe the parameters of the texture image,
such as height,
width,
width of the border,
level-of-detail number
(see _cmnd(TexParameter)),
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 _cmnd(DrawPixels).
.P
If _param1 is _const(PROXY_TEXTURE_2D), no data is read from _param9, 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 sets
all of the image state to 0,
but does not generate an error (see _cmnd(GetError)). To query for an
entire mipmap array, use an image array level greater than or equal to
1. 
.P 
If _param1 is _const(TEXTURE_2D),
data is read from _param9 as a sequence of signed or unsigned bytes,
shorts,
or longs,
or single-precision floating-point values,
depending on _param8. 
These values are grouped into sets of one,
two,
three,
or four values,
depending on _param7,
to form elements. 
If _param8 is _const(BITMAP),
the data is considered as a string of unsigned bytes (and
_param7 must be _const(COLOR_INDEX)). 
.bp
Each data byte is treated as eight 1-bit elements,
with bit ordering determined by _const(UNPACK_LSB_FIRST)
(see _cmnd(PixelStore)).
.P
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.
.P
_param7 determines the composition of each element in _param9.
It can assume one of eleven symbolic values:
.TP 10
_const(COLOR_INDEX)
Each element is a single value,
a color index. 
The GL converts 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 _const(INDEX_SHIFT),
and added to _const(INDEX_OFFSET)
(see 
.br
_cmnd(PixelTransfer)). 
The resulting index is converted to a set of color components
using the
_const(PIXEL_MAP_I_TO_R),
_const(PIXEL_MAP_I_TO_G),
_const(PIXEL_MAP_I_TO_B), and
_const(PIXEL_MAP_I_TO_A) tables,
and clamped to the range [0,1].
.TP
_const(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 component is then multiplied by the signed scale factor _const(c_SCALE),
added to the signed bias _const(c_BIAS),
and clamped to the range [0,1]
(see _cmnd(PixelTransfer)).
.TP
_const(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 component is then multiplied by the signed scale factor _const(c_SCALE),
added to the signed bias _const(c_BIAS),
and clamped to the range [0,1]
(see _cmnd(PixelTransfer)).
.TP
_const(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 component is then multiplied by the signed scale factor _const(c_SCALE),
added to the signed bias _const(c_BIAS),
and clamped to the range [0,1]
(see _cmnd(PixelTransfer)).
.TP
_const(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 _const(c_SCALE),
added to the signed bias _const(c_BIAS),
and clamped to the range [0,1]
(see _cmnd(PixelTransfer)).
.TP
_const(RGB)
.TP
_const(BGR)
Each element is an RGB triple.
The GL converts it to floating point and assembles it into an RGBA element
by attaching 1 for alpha.
Each component is then multiplied by the signed scale factor _const(c_SCALE),
added to the signed bias _const(c_BIAS),
and clamped to the range [0,1]
(see 
.br
_cmnd(PixelTransfer)).
.TP
_const(RGBA)
.TP
_const(BGRA)
_C_ .TP
_C_ _const(ABGR_EXT)
Each element contains all four components.
Each component is multiplied by the signed scale factor _const(c_SCALE),
added to the signed bias _const(c_BIAS),
and clamped to the range [0,1]
(see _cmnd(PixelTransfer)).
.TP
_const(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 _const(c_SCALE),
added to the signed bias _const(c_BIAS),
and clamped to the range [0,1]
(see _cmnd(PixelTransfer)).
.TP
_const(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 _const(c_SCALE),
added to the signed bias _const(c_BIAS),
and clamped to the range [0,1]
(see 
.br
_cmnd(PixelTransfer)).
.P
Refer to the _cmnd(DrawPixels) reference page for a description of
the acceptable values for the _param8 parameter.
.P
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 _param3. The GL will choose an internal
representation that closely approximates that requested by _param3, but
it may not match exactly.
(The representations specified by _const(LUMINANCE),
_const(LUMINANCE_ALPHA), _const(RGB),
and _const(RGBA) must match exactly. The numeric values 1, 2, 3, and 4
may also be used to specify the above representations.)
.P
Use the _const(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
_cmnd(GetTexLevelParameter).
If the texture cannot be accommodated, texture state is set to 0.
.P
A one-component texture image uses only the red component of the RGBA
color extracted from _param9. 
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. 
.SH NOTES
Texturing has no effect in color index mode.
.P
If the _arbstring(imaging) extension is supported, RGBA elements may
also be processed by the imaging pipeline.  The following stages may be
applied to an RGBA color before color component clamping to the range
[0,\ 1]:
.TP 3
1. Color component replacement by the color table specified for
_const(COLOR_TABLE), if enabled. See _cmnd(ColorTable).
.TP
2. Two-dimensional Convolution filtering, if enabled. See
_cmnd(ConvolutionFilter1D).
.IP
If a convolution filter changes the __width of the texture (by
processing with a _const(CONVOLUTION_BORDER_MODE) of _const(REDUCE), for 
example), the _param4 must $2 sup n + 2 ( _eqnparam5 )$, for some
integer $n$, and _param5 must be $2 sup m + ( _eqnparam6 )$, for some
integer $m$,  after filtering.
.TP
3. RGBA components may be multiplied by _const(POST_CONVOLUTION_c_SCALE), 
and added to _const(POST_CONVOLUTION_c_BIAS), if enabled.  See 
_cmnd(PixelTransfer).
.TP
4. Color component replacement by the color table specified for
_const(POST_CONVOLUTION_COLOR_TABLE), if enabled.  See _cmnd(ColorTable).
.TP
5. Transformation by the color matrix.  See _cmnd(MatrixMode).
.TP
6. RGBA components may be multiplied by _const(POST_COLOR_MATRIX_c_SCALE), 
and added to _const(POST_COLOR_MATRIX_c_BIAS), if enabled.  See 
_cmnd(PixelTransfer).
.TP
7. Color component replacement by the color table specified for
_const(POST_COLOR_MATRIX_COLOR_TABLE), if enabled.  See
_cmnd(ColorTable).
.P
The texture image can be represented by the same data formats
as the pixels in a _cmnd(DrawPixels) command,
except that _const(STENCIL_INDEX) and _const(DEPTH_COMPONENT)
cannot be used.
_cmnd(PixelStore) and _cmnd(PixelTransfer) modes affect texture images
in exactly the way they affect _cmnd(DrawPixels).
.P
_C_ _const(ABGR_EXT) is
_C_ part of the _extname(EXT_abgr) extension, not part of
_C_ the core GL command set.  If _extstring(EXT_abgr) is included
_C_ in the string returned by _cmnd(GetString), when called with
_C_ argument _const(EXTENSIONS), extension _extname(EXT_abgr) is
_C_ supported by the GL.
.P
_cmnd and _const(PROXY_TEXTURE_2D) are available only if the GL
version is 1.1 or greater. 
.P
Internal formats other than 1, 2, 3, or 4 may be used only if the GL
version is 1.1 or greater.
.P
In GL version 1.1 or greater, _param9 may be a null pointer. 
In this case texture memory is
allocated to accommodate a texture of width _param4 and height _param5.
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.
.P
Formats _const(BGR), and _const(BGRA) and types
_const(UNSIGNED_BYTE_3_3_2),
_const(UNSIGNED_BYTE_2_3_3_REV),
_const(UNSIGNED_SHORT_5_6_5),
_const(UNSIGNED_SHORT_5_6_5_REV),
_const(UNSIGNED_SHORT_4_4_4_4),
_const(UNSIGNED_SHORT_4_4_4_4_REV),
_const(UNSIGNED_SHORT_5_5_5_1),
_const(UNSIGNED_SHORT_1_5_5_5_REV),
_const(UNSIGNED_INT_8_8_8_8),
_const(UNSIGNED_INT_8_8_8_8_REV),
_const(UNSIGNED_INT_10_10_10_2), and
_const(UNSIGNED_INT_2_10_10_10_REV) are available only if the GL version 
is 1.2 or greater.
.P
When the _arbstring(multitexture) extension is supported, _cmnd
specifies the two-dimensional texture for the current texture unit,
specified with _cmnd(ActiveTextureARB).
.SH ERRORS
_const(INVALID_ENUM) is generated if _param1 is not _const(TEXTURE_2D)
or _const(PROXY_TEXTURE_2D).
.P
_const(INVALID_ENUM) is generated if _param7 is not an accepted
format constant.
Format constants other than _const(STENCIL_INDEX) and _const(DEPTH_COMPONENT)
are accepted.
.P
_const(INVALID_ENUM) is generated if _param8 is not a type constant.
.P
_const(INVALID_ENUM) is generated if _param8 is _const(BITMAP) and
_param7 is not _const(COLOR_INDEX).
.P
_const(INVALID_VALUE) is generated if _param2 is less than 0.
.P 
_const(INVALID_VALUE) may be generated if _param2 is greater than $log
sub 2$\f2max\fP,
where \f2max\fP is the returned value of _const(MAX_TEXTURE_SIZE).
.P
_const(INVALID_VALUE) is generated if _param3 is not 1, 2, 3, 4, or one of the 
accepted resolution and format symbolic constants.
.P
_const(INVALID_VALUE) is generated if _param4 or _param5 is less than 0
or greater than 2 + _const(MAX_TEXTURE_SIZE),
or if either cannot be represented as $2 sup k ~+~ 2(_eqnparam6)$ for some
integer value of \f2k\fP.
.P
_const(INVALID_VALUE) is generated if _param6 is not 0 or 1.
.P
_const(INVALID_OPERATION) is generated if _cmnd
is executed between the execution of _cmnd(Begin)
and the corresponding execution of _cmnd(End).
.P
_const(INVALID_OPERATION) is generated if _param8 is one of
_const(UNSIGNED_BYTE_3_3_2),
_const(UNSIGNED_BYTE_2_3_3_REV),
_const(UNSIGNED_SHORT_5_6_5), or
_const(UNSIGNED_SHORT_5_6_5_REV)
and _param7 is not _const(RGB).
.P
_const(INVALID_OPERATION) is generated if _param8 is one of
_const(UNSIGNED_SHORT_4_4_4_4),
_const(UNSIGNED_SHORT_4_4_4_4_REV),
_const(UNSIGNED_SHORT_5_5_5_1),
_const(UNSIGNED_SHORT_1_5_5_5_REV),
_const(UNSIGNED_INT_8_8_8_8),
_const(UNSIGNED_INT_8_8_8_8_REV),
_const(UNSIGNED_INT_10_10_10_2), or
_const(UNSIGNED_INT_2_10_10_10_REV)
and _param7 is neither _const(RGBA) nor _const(BGRA).
.SH ASSOCIATED GETS
_cmnd(GetTexImage)
.br
_cmnd(IsEnabled) with argument _const(TEXTURE_2D)
.SH SEE ALSO
_cmnd(ColorTable),
_cmnd(ConvolutionFilter2D),
_cmnd(CopyPixels),
_cmnd(CopyTexImage1D),
_cmnd(CopyTexImage2D),
_cmnd(CopyTexSubImage1D),
_cmnd(CopyTexSubImage2D),
_cmnd(CopyTexSubImage3D),
_cmnd(DrawPixels),
_cmnd(MatrixMode),
_cmnd(PixelStore),
_cmnd(PixelTransfer),
_cmnd(SeparableFilter2D),
_cmnd(TexEnv),
_cmnd(TexGen),
_cmnd(TexImage1D),
_cmnd(TexImage3D),
_cmnd(TexSubImage1D),
_cmnd(TexSubImage2D),
_cmnd(TexSubImage3D),
_cmnd(TexParameter)