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NAME

       glGetTextureSubImage - retrieve a sub-region of a texture image from a texture object

C SPECIFICATION

       void glGetTextureSubImage(GLuint texture, GLint level, GLint xoffset, GLint yoffset,
                                 GLint zoffset, GLsizei width, GLsizei height, GLsizei depth,
                                 GLenum format, GLenum type, GLsizei bufSize, void *pixels);

PARAMETERS

       texture
           Specifies the name of the source texture object. Must be GL_TEXTURE_1D,
           GL_TEXTURE_1D_ARRAY, GL_TEXTURE_2D, GL_TEXTURE_2D_ARRAY, GL_TEXTURE_3D,
           GL_TEXTURE_CUBE_MAP, GL_TEXTURE_CUBE_MAP_ARRAY or GL_TEXTURE_RECTANGLE. In specific,
           buffer and multisample textures are not permitted.

       level
           Specifies the level-of-detail number. Level 0 is the base image level. Level $n$ is
           the $n$th mipmap reduction image.

       xoffset
           Specifies a texel offset in the x direction within the texture array.

       yoffset
           Specifies a texel offset in the y direction within the texture array.

       zoffset
           Specifies a texel offset in the z direction within the texture array.

       width
           Specifies the width of the texture subimage.

       height
           Specifies the height of the texture subimage.

       depth
           Specifies the depth of the texture subimage.

       format
           Specifies the format of the pixel data. The following symbolic values are accepted:
           GL_RED, GL_RG, GL_RGB, GL_BGR, GL_RGBA, GL_BGRA, GL_DEPTH_COMPONENT and
           GL_STENCIL_INDEX.

       type
           Specifies the data type of the pixel data. The following symbolic values are accepted:
           GL_UNSIGNED_BYTE, GL_BYTE, 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.

       bufSize
           Specifies the size of the buffer to receive the retrieved pixel data.

       pixels
           Returns the texture subimage. Should be a pointer to an array of the type specified by
           type.

DESCRIPTION

       glGetTextureSubImage returns a texture subimage into pixels.

       texture is the name of the source texture object and must not be a buffer or multisample
       texture. The effective target parameter is the value of GL_TEXTURE_TARGET for texture.
       Level, format, type and pixels have the same meaning as for glGetTexImage.  bufSize is the
       size of the buffer to receive the retrieved pixel data.

       For cube map textures, the behavior is as though GetTextureImage were called, but only
       texels from the requested cube map faces (selected by zoffset and depth, as described
       below) were returned.

       xoffset, yoffset and zoffset values indicate the position of the subregion to return.
       width, height and depth indicate the size of the region to return. These parameters have
       the same meaning as for glTexSubImage3D, though for one- and two-dimensional textures
       there are extra restrictions, described in the errors section below.

       For one-dimensional array textures, yoffset is interpreted as the first layer to access
       and height is the number of layers to access.

       For two-dimensional array textures, zoffset is interpreted as the first layer to access
       and depth is the number of layers to access.

       Cube map textures are treated as an array of six slices in the z-dimension, where the
       value of zoffset is interpreted as specifying the cube map face for the corresponding
       layer (as presented in the table below) and depth is the number of faces to access:

       ┌─────────────┬────────────────────────────────┐
       │Layer number │ Cube Map Face                  │
       ├─────────────┼────────────────────────────────┤
       │0            │ GL_TEXTURE_CUBE_MAP_POSITIVE_X │
       ├─────────────┼────────────────────────────────┤
       │1            │ GL_TEXTURE_CUBE_MAP_NEGATIVE_X │
       ├─────────────┼────────────────────────────────┤
       │2            │ GL_TEXTURE_CUBE_MAP_POSITIVE_Y │
       ├─────────────┼────────────────────────────────┤
       │3            │ GL_TEXTURE_CUBE_MAP_NEGATIVE_Y │
       ├─────────────┼────────────────────────────────┤
       │4            │ GL_TEXTURE_CUBE_MAP_POSITIVE_Z │
       ├─────────────┼────────────────────────────────┤
       │5            │ GL_TEXTURE_CUBE_MAP_NEGATIVE_Z │
       └─────────────┴────────────────────────────────┘

       For cube map array textures, zoffset is the first layer-face to access, and depth is the
       number of layer-faces to access. A layer-face described by $k$ is translated into an array
       layer and face according to $$ layer = \left\lfloor { layer \over 6 } \right\rfloor$$ and
       $$ face = k \bmod 6. $$

       Component groups from the specified sub-region are packed and placed into memory as
       described for glGetTextureImage, starting with the texel at (xoffset, yoffset, zoffset).

ERRORS

       GL_INVALID_VALUE error is generated if texture is not the name of an existing texture
       object.

       GL_INVALID_OPERATION error is generated if texture is the name of a buffer or multisample
       texture.

       GL_INVALID_VALUE is generated if xoffset, yoffset or zoffset are negative.

       GL_INVALID_VALUE is generated if xoffset + width is greater than the texture's width,
       yoffset + height is greater than the texture's height, or zoffset + depth is greater than
       the texture's depth.

       GL_INVALID_VALUE error is generated if the effective target is GL_TEXTURE_1D and either
       yoffset is not zero, or height is not one.

       GL_INVALID_VALUE error is generated if the effective target is GL_TEXTURE_1D,
       GL_TEXTURE_1D_ARRAY, GL_TEXTURE_2D or GL_TEXTURE_RECTANGLE and either zoffset is not zero,
       or depth is not one.

       GL_INVALID_OPERATION error is generated if the buffer size required to store the requested
       data is greater than bufSize.

VERSION SUPPORT

       ┌─────────────────────┬───────────────────────────────────────────────────────────────────────┐
       │                     │                OpenGL Version                                         │
       ├─────────────────────┼─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┤
       │Function2.02.13.03.13.23.34.04.14.24.34.44.5 │
       │/                    │     │     │     │     │     │     │     │     │     │     │     │     │
       │Feature              │     │     │     │     │     │     │     │     │     │     │     │     │
       │Name                 │     │     │     │     │     │     │     │     │     │     │     │     │
       ├─────────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
       │glGetTextureSubImage │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  -  │  ✔  │
       └─────────────────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┘

SEE ALSO

       glGetTexImage(),

       glGetTextureImage, glReadPixels(), glTexImage1D(), glTexImage2D(), glTexImage3D(),
       glTexSubImage1D(), glTexSubImage2D(), glTexSubImage3D()

COPYRIGHT

       Copyright © 2014 Khronos Group. This material may be distributed subject to the terms and
       conditions set forth in the Open Publication License, v 1.0, 8 June 1999.
       http://opencontent.org/openpub/.

COPYRIGHT

       Copyright © 2014 Khronos Group

[FIXME: source]                             01/03/2018                   GLGETTEXTURESUBIMAGE(3G)