Index for Section 3G

Alphabetical listing for G

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glGetTexImage(3G)
NAME
  glGetTexImage - return a texture image

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

Index for Section 3G

Alphabetical listing for G

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