NAME
fglTexImage2D - specify a two-dimensional texture image
FORTRAN SPECIFICATION
SUBROUTINE fglTexImage2D( INTEGER*4 target,
INTEGER*4 level,
INTEGER*4 internalformat,
INTEGER*4 width,
INTEGER*4 height,
INTEGER*4 border,
INTEGER*4 format,
INTEGER*4 type,
CHARACTER*8 pixels )
PARAMETERS
target Specifies the target texture. Must be
GL_TEXTURE_2D or GL_PROXY_TEXTURE_2D.
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 texture. 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_LUMINANCE_ALPHA,
GL_LUMINANCE4_ALPHA4, GL_LUMINANCE6_ALPHA2,
GL_LUMINANCE8_ALPHA8, GL_LUMINANCE12_ALPHA4,
GL_LUMINANCE12_ALPHA12,
GL_LUMINANCE16_ALPHA16, GL_INTENSITY,
GL_INTENSITY4, GL_INTENSITY8,
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, or GL_RGBA16.
width Specifies the width of the texture image.
Must be 2n+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 2m+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_LUMINANCE, and
GL_LUMINANCE_ALPHA.
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, 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 graphical primitive for which texturing is enabled. To
enable and disable two-dimensional texturing, call fglEnable
and fglDisable with argument GL_TEXTURE_2D.
To define texture images, call fglTexImage2D. The arguments
describe the parameters of the texture image, such as
height, width, width of the border, level-of-detail number
(see fglTexParameter), 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 fglDrawPixels.
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 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
fglGetError). To query for an entire mipmap array, use an
image array level greater than or equal to 1.
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 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. 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 fglPixelStore).
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.
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 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 GL_INDEX_SHIFT, and added to
GL_INDEX_OFFSET (see
fglPixelTransfer). 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 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 fglPixelTransfer).
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 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 fglPixelTransfer).
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 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 fglPixelTransfer).
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 fglPixelTransfer).
GL_RGB 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
GL_c_SCALE, added to the signed bias GL_c_BIAS,
and clamped to the range [0,1] (see
fglPixelTransfer).
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
fglPixelTransfer).
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 fglPixelTransfer).
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
fglPixelTransfer).
Refer to the fglDrawPixels 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 representations.)
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 fglGetTexLevelParameter. 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 fglDrawPixels command, except
that GL_STENCIL_INDEX and GL_DEPTH_COMPONENT cannot be used.
fglPixelStore and fglPixelTransfer modes affect texture
images in exactly the way they affect fglDrawPixels.
fglTexImage2D and GL_PROXY_TEXTURE_2D 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
uninitialized portion of the texture image to a primitive.
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 constant. Format constants other than
GL_STENCIL_INDEX and GL_DEPTH_COMPONENT 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
log max, 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 represented as 2k+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 fglTexImage2D is
executed between the execution of fglBegin and the
corresponding execution of fglEnd.
ASSOCIATED GETS
fglGetTexImage
fglIsEnabled with argument GL_TEXTURE_2D
SEE ALSO
fglCopyPixels, fglCopyTexImage1D, fglCopyTexImage2D,
fglCopyTexSubImage1D, fglCopyTexSubImage2D, fglDrawPixels,
fglPixelStore, fglPixelTransfer, fglTexEnv, fglTexGen,
fglTexImage1D, fglTexSubImage1D, fglTexSubImage2D,
fglTexParameter