Страницы справочника OS X

Эта страница руководства является частью версии 5.0 Инструментов XCode

Читать страницы руководства

GLGETTEXIMAGE(3G)                                                                          GLGETTEXIMAGE(3G)



NAME
       glGetTexImage - return a texture image


C SPECIFICATION
       void glGetTexImage( GLenum target,
                           GLint level,
                           GLenum format,
                           GLenum type,
                           GLvoid *pixels )


PARAMETERS
       target  Specifies  which  texture is to be obtained.  GL_TEXTURE_1D, GL_TEXTURE_2D, and GL_TEXTURE_3D
               are accepted.

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

       format  Specifies  a  pixel   for  the  returned  data.   The supported formats are GL_RED, GL_GREEN,
               GL_BLUE, GL_ALPHA, GL_RGB, GL_BGR, GL_RGBA, GL_BGRA, GL_LUMINANCE, and GL_LUMINANCE_ALPHA.

       type    Specifies a pixel type for the returned data.   The  supported  types  are  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.

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

DESCRIPTION
       glGetTexImage returns a texture image into pixels.  target  specifies  whether  the  desired  texture
       image is one specified by glTexImage1D (GL_TEXTURE_1D), glTexImage2D (GL_TEXTURE_2D), or glTexImage3D
       (GL_TEXTURE_3D).  level specifies the level-of-detail number of the desired image.  format  and  type
       specify  the   and  type  of  the  desired  image  array.   See  the reference pages glTexImage1D and
       glDrawPixels for a description of the acceptable values for the format and type  parameters,  respec-tively. respectively.
       tively.

       To  understand  the operation of glGetTexImage, consider the selected internal four-component texture
       image to be an RGBA color buffer the size of the image.  The  semantics  of  glGetTexImage  are  then
       identical  to  those  of  glReadPixels, with the exception that no pixel transfer operations are per-formed, performed,
       formed, when called with the same format and type, with x and y set to 0, width set to the  width  of
       the  texture  image (including border if one was specified), and height set to 1 for 1D images, or to
       the height of the texture image (including border if one was specified) for 2D images.   Because  the
       internal  texture  image  is  an  RGBA  image,  pixel  formats  GL_COLOR_INDEX, GL_STENCIL_INDEX, and
       GL_DEPTH_COMPONENT are not accepted, and pixel type GL_BITMAP is not accepted.

       If the selected texture image does not contain four components, the following mappings  are  applied.
       Single-component  textures  are  treated  as RGBA buffers with red set to the single-component value,
       green set to 0,  blue set to 0, and alpha set to 1.   Two-component  textures  are  treated  as  RGBA
       buffers  with  red  set  to the value of component zero, alpha set to the value of component one, and
       green and blue set to 0.  Finally, three-component textures are treated as RGBA buffers with red  set
       to component zero, green set to component one, blue set to component two, and alpha set to 1.

       To  determine  the required size of pixels, use glGetTexLevelParameter to determine the dimensions of
       the internal texture image, then scale the required number of pixels by the storage required for each
       pixel,  based  on  format and type.  Be sure to take the pixel storage parameters into account, espe-cially especially
       cially GL_PACK_ALIGNMENT.

NOTES
       If an error is generated, no change is made to the contents of pixels.

       When the GL_ARB_multitexture extension is supported, glGetTexImage returns the texture image for  the
       active texture unit.

       The     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, GL_UNSIGNED_INT_2_10_10_10_REV, and the for-mats formats
       mats GL_BGR, and GL_BGRA are available only if the GL version is 1.2 or greater.

ERRORS
       GL_INVALID_ENUM is generated if target, format, or type is not an accepted value.

       GL_INVALID_VALUE is generated if level is less than 0.

       GL_INVALID_VALUE may be generated if level is greater than log2(max), where max is the returned value
       of GL_MAX_TEXTURE_SIZE.

       GL_INVALID_OPERATION is generated if glGetTexImage is executed between the execution of  glBegin  and
       the corresponding execution of glEnd.

       GL_INVALID_OPERATION     is     returned     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    returned    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 or GL_BGRA.

ASSOCIATED GETS
       glGetTexLevelParameter with argument GL_TEXTURE_WIDTH
       glGetTexLevelParameter with argument GL_TEXTURE_HEIGHT
       glGetTexLevelParameter with argument GL_TEXTURE_BORDER
       glGetTexLevelParameter with argument GL_TEXTURE_INTERNALFORMAT
       glGet with arguments GL_PACK_ALIGNMENT and others

SEE ALSO
       glActiveTextureARB(3G),  glDrawPixels(3G),  glReadPixels(3G),  glTexEnv(3G),  glTexGen(3G),  glTexImage1D(3G),  glTexImage2D(3G),
       glTexImage3D(3G), glTexSubImage1D(3G), glTexSubImage2D(3G), glTexSubImage3D(3G), glTexParameter(3G)




                                                                                           GLGETTEXIMAGE(3G)