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glTexImage2D(3G)
NAME
glTexImage2D - specify a two-dimensional texture image
SYNOPSIS
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 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 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 of the pixel data. The following symbolic values are
accepted: GL_COLOR_INDEX, GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB,
GL_BGR GL_RGBA, GL_BGRA, 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, GL_FLOAT,
GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV,
GL_UNSIGNED_SHORT_5_6_5, GL_UNSIGNED_SHORT_5_6_5_REV,
GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV,
GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV,
GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV,
GL_UNSIGNED_INT_10_10_10_2, and GL_UNSIGNED_INT_2_10_10_10_REV.
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 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 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 glGetError()). 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
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.
format determines the composition of each element in pixels. It can assume
one of eleven 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
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 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_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 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 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_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
GL_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 GL_c_SCALE,
added to the signed bias GL_c_BIAS, and clamped to the range [0,1] (see
glPixelTransfer()).
GL_RGBA
GL_BGRA
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 , it can request the resolution and 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 . 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.
If the GL_ARB_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]:
1. Color component replacement by the color table specified for
GL_COLOR_TABLE, if enabled. See glColorTable().
2. Two-dimensional Convolution filtering, if enabled. See
glConvolutionFilter1D().
If a convolution filter changes the __width of the texture (by
processing with a GL_CONVOLUTION_BORDER_MODE of GL_REDUCE, for
example), the width must 2^n + 2 ( height ), for some integer n, and
height must be 2^m + ( border ), for some integer m, after filtering.
3. RGBA components may be multiplied by GL_POST_CONVOLUTION_c_SCALE,
and added to GL_POST_CONVOLUTION_c_BIAS, if enabled. See
glPixelTransfer().
4. Color component replacement by the color table specified for
GL_POST_CONVOLUTION_COLOR_TABLE, if enabled. See glColorTable().
5. Transformation by the color matrix. See glMatrixMode.
6. RGBA components may be multiplied by GL_POST_COLOR_MATRIX_c_SCALE,
and added to GL_POST_COLOR_MATRIX_c_BIAS, if enabled. See
glPixelTransfer().
7. Color component replacement by the color table specified for
GL_POST_COLOR_MATRIX_COLOR_TABLE, if enabled. See glColorTable().
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 glDrawPixels().
glTexImage2D() and GL_PROXY_TEXTURE_2D are available only if the GL version
is 1.1 or greater.
Internal formats other than 1, 2, 3, or 4 may be used only 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.
Formats GL_BGR, and GL_BGRA and types GL_UNSIGNED_BYTE_3_3_2,
GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5,
GL_UNSIGNED_SHORT_5_6_5_REV, GL_UNSIGNED_SHORT_4_4_4_4,
GL_UNSIGNED_SHORT_4_4_4_4_REV, GL_UNSIGNED_SHORT_5_5_5_1,
GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8,
GL_UNSIGNED_INT_8_8_8_8_REV, GL_UNSIGNED_INT_10_10_10_2, and
GL_UNSIGNED_INT_2_10_10_10_REV are available only if the GL version is 1.2
or greater.
When the GL_ARB_multitexture extension is supported, glTexImage2D()
specifies the two-dimensional texture for the current texture unit,
specified with glActiveTextureARB().
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 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 sub 2max,
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 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 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_OPERATION is generated if type is one of GL_UNSIGNED_BYTE_3_3_2,
GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5, or
GL_UNSIGNED_SHORT_5_6_5_REV and format is not GL_RGB.
GL_INVALID_OPERATION is generated if type is one of
GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV,
GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV,
GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV,
GL_UNSIGNED_INT_10_10_10_2, or GL_UNSIGNED_INT_2_10_10_10_REV and format is
neither GL_RGBA nor GL_BGRA.
ASSOCIATED GETS
glGetTexImage()
glIsEnabled() with argument GL_TEXTURE_2D
SEE ALSO
glColorTable(3), glConvolutionFilter2D(3), glCopyPixels(3),
glCopyTexImage1D(3), glCopyTexImage2D(3), glCopyTexSubImage1D(3),
glCopyTexSubImage2D(3), glCopyTexSubImage3D(3), , glDrawPixels(3),
glMatrixMode(3), glPixelStore(3), glPixelTransfer(3),
glSeparableFilter2D(3), glTexEnv(3), glTexGen(3), glTexImage1D(3),
glTexSubImage1D(3), glTexImage3D(3), glTexSubImage2D(3),
glTexSubImage3D(3), glTexParameter(3)
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