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  man pages->Tru64 Unix man pages -> glGetTexImage (3)              
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glGetTexImage(3G)

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NAME    [Toc]    [Back]

       glGetTexImage - return a texture image

SYNOPSIS    [Toc]    [Back]

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

PARAMETERS    [Toc]    [Back]

       Specifies which texture is to be obtained.  GL_TEXTURE_1D,
       GL_TEXTURE_2D, and GL_TEXTURE_3D are accepted.   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.  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.   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.   Returns the texture
       image. Should be a pointer to an array of the type  specified
 by type.

DESCRIPTION    [Toc]    [Back]

       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,
       respectively.

       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 performed, 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, especially GL_PACK_ALIGNMENT.

NOTES    [Toc]    [Back]

       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  formats GL_BGR,
       and GL_BGRA are available only if the GL version is 1.2 or
       greater.

ERRORS    [Toc]    [Back]

       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
       log  sub  2  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    [Toc]    [Back]

       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    [Toc]    [Back]

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



                                                glGetTexImage(3G)
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