1GLGETTEXIMAGE(3G) GLGETTEXIMAGE(3G)
2
6 glGetTexImage - return a texture image
7
10 void glGetTexImage( GLenum target,
11 GLint level,
12 GLenum format,
13 GLenum type,
14 GLvoid *pixels )
15
18 target Specifies which texture is to be obtained. GL_TEXTURE_1D,
19 GL_TEXTURE_2D, and GL_TEXTURE_3D are accepted.
20 level Specifies the level-of-detail number of the desired image.
22 Level 0 is the base image level. Level n is the nth mipmap
23 reduction image.
24 format Specifies a pixel for the returned data. The supported for‐
26 mats are GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_BGR,
27 GL_RGBA, GL_BGRA, GL_LUMINANCE, and GL_LUMINANCE_ALPHA.
28 type Specifies a pixel type for the returned data. The supported
30 types are GL_UNSIGNED_BYTE, GL_BYTE, GL_UNSIGNED_SHORT,
31 GL_SHORT, GL_UNSIGNED_INT, GL_INT, GL_FLOAT,
32 GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV,
33 GL_UNSIGNED_SHORT_5_6_5, GL_UNSIGNED_SHORT_5_6_5_REV,
34 GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV,
35 GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV,
36 GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV,
37 GL_UNSIGNED_INT_10_10_10_2, and GL_UNSIGNED_INT_2_10_10_10_REV.
38 pixels Returns the texture image. Should be a pointer to an array of
40 the type specified by type.
41
43 glGetTexImage returns a texture image into pixels. target specifies
44 whether the desired texture image is one specified by glTexImage1D (‐
45 GL_TEXTURE_1D), glTexImage2D (GL_TEXTURE_2D), or glTexImage3D (‐
46 GL_TEXTURE_3D). level specifies the level-of-detail number of the
47 desired image. format and type specify the and type of the desired
48 image array. See the reference pages glTexImage1D and glDrawPixels for
49 a description of the acceptable values for the format and type parame‐
50 ters, respectively.
51 To understand the operation of glGetTexImage, consider the selected
53 internal four-component texture image to be an RGBA color buffer the
54 size of the image. The semantics of glGetTexImage are then identical
55 to those of glReadPixels, with the exception that no pixel transfer
56 operations are performed, when called with the same format and type,
57 with x and y set to 0, width set to the width of the texture image
58 (including border if one was specified), and height set to 1 for 1D
59 images, or to the height of the texture image (including border if one
60 was specified) for 2D images. Because the internal texture image is an
61 RGBA image, pixel formats GL_COLOR_INDEX, GL_STENCIL_INDEX, and
62 GL_DEPTH_COMPONENT are not accepted, and pixel type GL_BITMAP is not
63 accepted.
64 If the selected texture image does not contain four components, the
66 following mappings are applied. Single-component textures are treated
67 as RGBA buffers with red set to the single-component value, green set
68 to 0, blue set to 0, and alpha set to 1. Two-component textures are
69 treated as RGBA buffers with red set to the value of component zero,
70 alpha set to the value of component one, and green and blue set to 0.
71 Finally, three-component textures are treated as RGBA buffers with red
72 set to component zero, green set to component one, blue set to compo‐
73 nent two, and alpha set to 1.
74 To determine the required size of pixels, use glGetTexLevelParameter to
76 determine the dimensions of the internal texture image, then scale the
77 required number of pixels by the storage required for each pixel, based
78 on format and type. Be sure to take the pixel storage parameters into
79 account, especially GL_PACK_ALIGNMENT.
80
82 If an error is generated, no change is made to the contents of pixels.
83 When the GL_ARB_multitexture extension is supported, glGetTexImage
85 returns the texture image for the active texture unit.
86 The types GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV,
88 GL_UNSIGNED_SHORT_5_6_5, GL_UNSIGNED_SHORT_5_6_5_REV,
89 GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV,
90 GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV,
91 GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV,
92 GL_UNSIGNED_INT_10_10_10_2, GL_UNSIGNED_INT_2_10_10_10_REV, and the
93 formats GL_BGR, and GL_BGRA are available only if the GL version is 1.2
94 or greater.
95
97 GL_INVALID_ENUM is generated if target, format, or type is not an
98 accepted value.
99 GL_INVALID_VALUE is generated if level is less than 0.
101 GL_INVALID_VALUE may be generated if level is greater than log2max,
103 where max is the returned value of GL_MAX_TEXTURE_SIZE.
104 GL_INVALID_OPERATION is generated if glGetTexImage is executed between
106 the execution of glBegin and the corresponding execution of glEnd.
107 GL_INVALID_OPERATION is returned if type is one of
109 GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV,
110 GL_UNSIGNED_SHORT_5_6_5, or GL_UNSIGNED_SHORT_5_6_5_REV and format is
111 not GL_RGB.
112 GL_INVALID_OPERATION is returned if type is one of
114 GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV,
115 GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV,
116 GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV,
117 GL_UNSIGNED_INT_10_10_10_2, or GL_UNSIGNED_INT_2_10_10_10_REV, and for‐
118 mat is neither GL_RGBA or GL_BGRA.
119
121 glGetTexLevelParameter with argument GL_TEXTURE_WIDTH
122 glGetTexLevelParameter with argument GL_TEXTURE_HEIGHT
123 glGetTexLevelParameter with argument GL_TEXTURE_BORDER
124 glGetTexLevelParameter with argument GL_TEXTURE_INTERNALFORMAT
125 glGet with arguments GL_PACK_ALIGNMENT and others
126
128 glActiveTextureARB(3G), glDrawPixels(3G), glReadPixels(3G),
129 glTexEnv(3G), glTexGen(3G), glTexImage1D(3G), glTexImage2D(3G),
130 glTexImage3D(3G), glTexSubImage1D(3G), glTexSubImage2D(3G),
131 glTexSubImage3D(3G), glTexParameter(3G)
132 GLGETTEXIMAGE(3G)