GlTexImage2D

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_glTexImage2D: specify a two-dimensional texture image


Syntax

 SUB _glTexImage2D (BYVAL target AS _UNSIGNED LONG, BYVAL level AS LONG, BYVAL internalformat AS LONG, BYVAL width AS LONG, BYVAL height AS LONG, BYVAL border AS LONG, BYVAL format AS _UNSIGNED LONG, BYVAL type AS _UNSIGNED LONG, pixels AS _OFFSET)
 void _glTexImage2D(GLenum target, GLint level, GLint internalFormat, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, const GLvoid * data);


target
Specifies the target texture. Must be _GL_TEXTURE_2D, _GL_PROXY_TEXTURE_2D, _GL_TEXTURE_1D_ARRAY, _GL_PROXY_TEXTURE_1D_ARRAY, _GL_TEXTURE_RECTANGLE, _GL_PROXY_TEXTURE_RECTANGLE, _GL_TEXTURE_CUBE_MAP_POSITIVE_X, _GL_TEXTURE_CUBE_MAP_NEGATIVE_X, _GL_TEXTURE_CUBE_MAP_POSITIVE_Y, _GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, _GL_TEXTURE_CUBE_MAP_POSITIVE_Z, _GL_TEXTURE_CUBE_MAP_NEGATIVE_Z, or _GL_PROXY_TEXTURE_CUBE_MAP.
level
Specifies the level-of-detail number. Level 0 is the base image level. Level n is the nth mipmap reduction image. If target is _GL_TEXTURE_RECTANGLE or _GL_PROXY_TEXTURE_RECTANGLE, level must be 0.
internalFormat
Specifies the number of color components in the texture. Must be one of base internal formats given in Table 1, one of the sized internal formats given in Table 2, or one of the compressed internal formats given in Table 3, below.
width
Specifies the width of the texture image. All implementations support texture images that are at least 1024 texels wide.
height
Specifies the height of the texture image, or the number of layers in a texture array, in the case of the _GL_TEXTURE_1D_ARRAY and _GL_PROXY_TEXTURE_1D_ARRAY targets. All implementations support 2D texture images that are at least 1024 texels high, and texture arrays that are at least 256 layers deep.
border
This value must be 0.

Template:Glapi pixeltransferupparams


Description

Texturing allows elements of an image array to be read by shaders.

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.

If target is _GL_PROXY_TEXTURE_2D, _GL_PROXY_TEXTURE_1D_ARRAY, _GL_PROXY_TEXTURE_CUBE_MAP, or _GL_PROXY_TEXTURE_RECTANGLE, no data is read from data, 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, _GL_TEXTURE_RECTANGLE or one of the _GL_TEXTURE_CUBE_MAP targets, data is read from data 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. Each data byte is treated as eight 1-bit elements, with bit ordering determined by _GL_UNPACK_LSB_FIRST (see _glPixelStore).

If target is _GL_TEXTURE_1D_ARRAY, data is interpreted as an array of one-dimensional images.

If a non-zero named buffer object is bound to the _GL_PIXEL_UNPACK_BUFFER target (see _glBindBuffer) while a texture image is specified, data is treated as a byte offset into the buffer object's data store.

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 data. It can assume one of these symbolic values:

_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].
_GL_RG
Each element is a red/green double. The GL converts it to floating point and assembles it into an RGBA element by attaching 0 for 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].
_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].
_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].
_GL_DEPTH_COMPONENT
Each element is a single depth value. The GL converts it to floating point, multiplies by the signed scale factor _GL_DEPTH_SCALE, adds the signed bias _GL_DEPTH_BIAS, and clamps to the range [0,1].
_GL_DEPTH_STENCIL
Each element is a pair of depth and stencil values. The depth component of the pair is interpreted as in _GL_DEPTH_COMPONENT. The stencil component is interpreted based on specified the depth + stencil internal format.

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_RED, _GL_RG, _GL_RGB, and _GL_RGBA must match exactly.)

internalFormat may be one of the base internal formats shown in Table 1, below

Template:Glapi baseformattable

internalFormat may also be one of the sized internal formats shown in Table 2, below

Template:Glapi internalformattable

Finally, internalFormat may also be one of the generic or compressed compressed texture formats shown in Table 3 below

Template:Glapi compressedformattable

If the internalFormat parameter is one of the generic compressed formats, _GL_COMPRESSED_RED, _GL_COMPRESSED_RG, _GL_COMPRESSED_RGB, or _GL_COMPRESSED_RGBA, the GL will replace the internal format with the symbolic constant for a specific internal format and compress the texture before storage. If no corresponding internal format is available, or the GL can not compress that image for any reason, the internal format is instead replaced with a corresponding base internal format.

If the internalFormat parameter is _GL_SRGB, _GL_SRGB8, _GL_SRGB_ALPHA, or _GL_SRGB8_ALPHA8, the texture is treated as if the red, green, or blue components are encoded in the sRGB color space. Any alpha component is left unchanged. The conversion from the sRGB encoded component c<sub>s</sub> to a linear component c<sub>l</sub> is:

Template:Glapi srgb equation

Assume c<sub>s</sub> is the sRGB component in the range [0,1].

Use the _GL_PROXY_TEXTURE_2D, _GL_PROXY_TEXTURE_1D_ARRAY, _GL_PROXY_TEXTURE_RECTANGLE, or _GL_PROXY_TEXTURE_CUBE_MAP 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 _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 data. A two-component image uses the R and G values. A three-component image uses the R, G, and B values. A four-component image uses all of the RGBA components.

Image-based shadowing can be enabled by comparing texture r coordinates to depth texture values to generate a boolean result. See _glTexParameter for details on texture comparison.


Notes:

The _glPixelStore mode affects texture images.

data 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.

_glTexImage2D specifies the two-dimensional texture for the current texture unit, specified with _glActiveTexture.


Errors

_GL_INVALID_ENUM is generated if target is not _GL_TEXTURE_2D, _GL_TEXTURE_1D_ARRAY, _GL_TEXTURE_RECTANGLE, _GL_PROXY_TEXTURE_2D, _GL_PROXY_TEXTURE_1D_ARRAY, _GL_PROXY_TEXTURE_RECTANGLE, _GL_PROXY_TEXTURE_CUBE_MAP, _GL_TEXTURE_CUBE_MAP_POSITIVE_X, _GL_TEXTURE_CUBE_MAP_NEGATIVE_X, _GL_TEXTURE_CUBE_MAP_POSITIVE_Y, _GL_TEXTURE_CUBE_MAP_NEGATIVE_Y, _GL_TEXTURE_CUBE_MAP_POSITIVE_Z, or _GL_TEXTURE_CUBE_MAP_NEGATIVE_Z.

_GL_INVALID_ENUM is generated if target is one of the six cube map 2D image targets and the width and height parameters are not equal.

_GL_INVALID_ENUM is generated if type is not a type constant.

_GL_INVALID_VALUE is generated if width is less than 0 or greater than _GL_MAX_TEXTURE_SIZE.

_GL_INVALID_VALUE is generated if target is not _GL_TEXTURE_1D_ARRAY or _GL_PROXY_TEXTURE_1D_ARRAY and height is less than 0 or greater than _GL_MAX_TEXTURE_SIZE.

_GL_INVALID_VALUE is generated if target is _GL_TEXTURE_1D_ARRAY or _GL_PROXY_TEXTURE_1D_ARRAY and height is less than 0 or greater than _GL_MAX_ARRAY_TEXTURE_LAYERS.

_GL_INVALID_VALUE is generated if level is less than 0.

_GL_INVALID_VALUE may be generated if level is greater than log<sub>2</sub>(max), where max is the returned value of _GL_MAX_TEXTURE_SIZE.

_GL_INVALID_VALUE is generated if internalFormat is not 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 _GL_MAX_TEXTURE_SIZE.

_GL_INVALID_VALUE is generated if border is not 0.

_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, _GL_UNSIGNED_SHORT_5_6_5_REV, or _GL_UNSIGNED_INT_10F_11F_11F_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, _GL_UNSIGNED_INT_2_10_10_10_REV, or _GL_UNSIGNED_INT_5_9_9_9_REV, and format is neither _GL_RGBA nor _GL_BGRA.

_GL_INVALID_OPERATION is generated if target is not _GL_TEXTURE_2D, _GL_PROXY_TEXTURE_2D, _GL_TEXTURE_RECTANGLE, or _GL_PROXY_TEXTURE_RECTANGLE, and internalFormat is _GL_DEPTH_COMPONENT, _GL_DEPTH_COMPONENT16, _GL_DEPTH_COMPONENT24, or _GL_DEPTH_COMPONENT32F.

_GL_INVALID_OPERATION is generated if format is _GL_DEPTH_COMPONENT and internalFormat is not _GL_DEPTH_COMPONENT, _GL_DEPTH_COMPONENT16, _GL_DEPTH_COMPONENT24, or _GL_DEPTH_COMPONENT32F.

_GL_INVALID_OPERATION is generated if internalFormat is _GL_DEPTH_COMPONENT, _GL_DEPTH_COMPONENT16, _GL_DEPTH_COMPONENT24, or _GL_DEPTH_COMPONENT32F, and format is not _GL_DEPTH_COMPONENT.

_GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to the _GL_PIXEL_UNPACK_BUFFER target and the buffer object's data store is currently mapped.

_GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to the _GL_PIXEL_UNPACK_BUFFER target and the data would be unpacked from the buffer object such that the memory reads required would exceed the data store size.

_GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to the _GL_PIXEL_UNPACK_BUFFER target and data is not evenly divisible into the number of bytes needed to store in memory a datum indicated by type.

_GL_INVALID_VALUE is generated if target is _GL_TEXTURE_RECTANGLE or _GL_PROXY_TEXTURE_RECTANGLE and level is not 0.


Use With:

_glGetTexImage

_glGet with argument _GL_PIXEL_UNPACK_BUFFER_BINDING


See also

SUB _GL _glActiveTexture, _glBindTexture, _glTexImage1D, _glTexImage2DMultisample, _glTexImage3D, _glTexImage3DMultisample, _glTexSubImage2D, _glPixelStore


Copyright: 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License.
For details, see http://oss.sgi.com/projects/FreeB/.



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Copyright 1991-2006 Silicon Graphics, Inc. Copyright 2011 Khronos Group. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.