Страницы справочника OS X

Эта страница руководства является частью версии 5.0 Инструментов XCode

Читать страницы руководства

GLGETTEXIMAGE(3G)                                OpenGL 3.3                                GLGETTEXIMAGE(3G)



NAME
       glGetTexImage - return a texture image

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

PARAMETERS
       target
           Specifies which texture is to be obtained.  GL_TEXTURE_1D, GL_TEXTURE_2D, GL_TEXTURE_3D,
           GL_TEXTURE_1D_ARRAY, GL_TEXTURE_2D_ARRAY, GL_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, and GL_TEXTURE_CUBE_MAP_NEGATIVE_Z 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 format for the returned data. The supported formats are GL_STENCIL_INDEX,
           GL_DEPTH_COMPONENT, GL_DEPTH_STENCIL, GL_RED, GL_GREEN, GL_BLUE, GL_RG, GL_RGB, GL_RGBA, GL_BGR,
           GL_BGRA, GL_RED_INTEGER, GL_GREEN_INTEGER, GL_BLUE_INTEGER, GL_RG_INTEGER, GL_RGB_INTEGER,
           GL_RGBA_INTEGER, GL_BGR_INTEGER, GL_BGRA_INTEGER.

       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_HALF_FLOAT, 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, GL_UNSIGNED_INT_2_10_10_10_REV,
           GL_UNSIGNED_INT_24_8, GL_UNSIGNED_INT_10F_11F_11F_REV, GL_UNSIGNED_INT_5_9_9_9_REV, and
           GL_FLOAT_32_UNSIGNED_INT_24_8_REV.

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

DESCRIPTION
       glGetTexImage returns a texture image into img.  target specifies whether the desired texture image
       is one specified by glTexImage1D() (GL_TEXTURE_1D), glTexImage2D() (GL_TEXTURE_1D_ARRAY,
       GL_TEXTURE_RECTANGLE, GL_TEXTURE_2D or any of GL_TEXTURE_CUBE_MAP_*), or glTexImage3D()
       (GL_TEXTURE_2D_ARRAY, GL_TEXTURE_3D).  level specifies the level-of-detail number of the desired
       image.  format and type specify the format and type of the desired image array. See the reference
       page for glTexImage1D() for a description of the acceptable values for the format and type
       parameters, respectively.

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

       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 and height set to 1 for 1D images, or to the height of the texture image for 2D
       images.

       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 img, 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 img.


       glGetTexImage returns the texture image for the active texture unit.

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 2 ^, max, where max is the returned
       value of GL_MAX_TEXTURE_SIZE.


       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, 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 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,
       GL_UNSIGNED_INT_2_10_10_10_REV, or GL_UNSIGNED_INT_5_9_9_9_REV and format is neither GL_RGBA or
       GL_BGRA.


       GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to the
       GL_PIXEL_PACK_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_PACK_BUFFER target and the data would be packed to the buffer object such that the memory
       writes 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_PACK_BUFFER target and img is not evenly divisible into the number of bytes needed to store
       in memory a datum indicated by type.

ASSOCIATED GETS
       glGetTexLevelParameter() with argument GL_TEXTURE_WIDTH


       glGetTexLevelParameter() with argument GL_TEXTURE_HEIGHT


       glGetTexLevelParameter() with argument GL_TEXTURE_INTERNAL_FORMAT


       glGet() with arguments GL_PACK_ALIGNMENT and others


       glGet() with argument GL_PIXEL_PACK_BUFFER_BINDING

SEE ALSO
       glActiveTexture(), glReadPixels(), glTexImage1D(), glTexImage2D(), glTexImage3D(), glTexSubImage1D(),
       glTexSubImage2D(), glTexSubImage3D(), glTexParameter()


COPYRIGHT
       Copyright (C) 1991-2006 Silicon Graphics, Inc. Copyright (C) 2010 Khronos Group. This document is
       licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.



OpenGL 3.3                                       03/08/2011                                GLGETTEXIMAGE(3G)