1GLCOPYCONVOLUTIONFIL(3G) OpenGL Manual GLCOPYCONVOLUTIONFIL(3G)
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6 glCopyConvolutionFilter2D - copy pixels into a two-dimensional
7 convolution filter
8
10 void glCopyConvolutionFilter2D(GLenum target, GLenum internalformat,
11 GLint x, GLint y, GLsizei width,
12 GLsizei height);
13
15 target
16 Must be GL_CONVOLUTION_2D.
17 internalformat
19 The internal format of the convolution filter kernel. The allowable
20 values are GL_ALPHA, GL_ALPHA4, GL_ALPHA8, GL_ALPHA12, GL_ALPHA16,
21 GL_LUMINANCE, GL_LUMINANCE4, GL_LUMINANCE8, GL_LUMINANCE12,
22 GL_LUMINANCE16, GL_LUMINANCE_ALPHA, GL_LUMINANCE4_ALPHA4,
23 GL_LUMINANCE6_ALPHA2, GL_LUMINANCE8_ALPHA8, GL_LUMINANCE12_ALPHA4,
24 GL_LUMINANCE12_ALPHA12, GL_LUMINANCE16_ALPHA16, GL_INTENSITY,
25 GL_INTENSITY4, GL_INTENSITY8, GL_INTENSITY12, GL_INTENSITY16,
26 GL_R3_G3_B2, GL_RGB, GL_RGB4, GL_RGB5, GL_RGB8, GL_RGB10, GL_RGB12,
27 GL_RGB16, GL_RGBA, GL_RGBA2, GL_RGBA4, GL_RGB5_A1, GL_RGBA8,
28 GL_RGB10_A2, GL_RGBA12, or GL_RGBA16.
29 x, y
31 The window space coordinates of the lower-left coordinate of the
32 pixel array to copy.
33 width
35 The width of the pixel array to copy.
36 height
38 The height of the pixel array to copy.
39
41 glCopyConvolutionFilter2D defines a two-dimensional convolution filter
42 kernel with pixels from the current GL_READ_BUFFER (rather than from
43 main memory, as is the case for glConvolutionFilter2D()).
44 The screen-aligned pixel rectangle with lower-left corner at (x,\ y),
46 width width and height height is used to define the convolution filter.
47 If any pixels within this region are outside the window that is
48 associated with the GL context, the values obtained for those pixels
49 are undefined.
50 The pixels in the rectangle are processed exactly as if glReadPixels()
52 had been called with format set to RGBA, but the process stops just
53 before final conversion. The R, G, B, and A components of each pixel
54 are next scaled by the four 2D GL_CONVOLUTION_FILTER_SCALE parameters
55 and biased by the four 2D GL_CONVOLUTION_FILTER_BIAS parameters. (The
56 scale and bias parameters are set by glConvolutionParameter() using the
57 GL_CONVOLUTION_2D target and the names GL_CONVOLUTION_FILTER_SCALE and
58 GL_CONVOLUTION_FILTER_BIAS. The parameters themselves are vectors of
59 four values that are applied to red, green, blue, and alpha, in that
60 order.) The R, G, B, and A values are not clamped to [0,1] at any time
61 during this process.
62 Each pixel is then converted to the internal format specified by
64 internalformat. This conversion simply maps the component values of the
65 pixel (R, G, B, and A) to the values included in the internal format
66 (red, green, blue, alpha, luminance, and intensity). The mapping is as
67 follows:
68 ┌─────────────────────────────────┬─────────────────────────────┬───────────────────────────────┬──────────────────────────────┬───────────────────────────────┬───────────────────────────────────┬───────────────────────────────────┐
70 │ │ │ │ │ │ │ │
71 │ Internal │ Red │ Green │ Blue │ Alpha │ Luminance │ Intensity │
72 │Format │ │ │ │ │ │ │
73 │ │ │ │ │ │ │ │
74 ├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
75 │GL_ALPHA │ │ │ │ A │ │ │
76 ├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
77 │GL_LUMINANCE │ │ │ │ │ R │ │
78 ├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
79 │GL_LUMINANCE_ALPHA │ │ │ │ A │ R │ │
80 ├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
81 │GL_INTENSITY │ │ │ │ │ │ R │
82 ├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
83 │GL_RGB │ R │ G │ B │ │ │ │
84 ├─────────────────────────────────┼─────────────────────────────┼───────────────────────────────┼──────────────────────────────┼───────────────────────────────┼───────────────────────────────────┼───────────────────────────────────┤
85 │GL_RGBA │ R │ G │ B │ A │ │ │
86 └─────────────────────────────────┴─────────────────────────────┴───────────────────────────────┴──────────────────────────────┴───────────────────────────────┴───────────────────────────────────┴───────────────────────────────────┘
87 The red, green, blue, alpha, luminance, and/or intensity components of
89 the resulting pixels are stored in floating-point rather than integer
90 format.
91 Pixel ordering is such that lower x screen coordinates correspond to
93 lower i filter image coordinates, and lower y screen coordinates
94 correspond to lower j filter image coordinates.
95 Note that after a convolution is performed, the resulting color
97 components are also scaled by their corresponding
98 GL_POST_CONVOLUTION_c_SCALE parameters and biased by their
99 corresponding GL_POST_CONVOLUTION_c_BIAS parameters (where c takes on
100 the values RED, GREEN, BLUE, and ALPHA). These parameters are set by
101 glPixelTransfer().
102
104 glCopyConvolutionFilter2D is present only if ARB_imaging is returned
105 when glGetString() is called with an argument of GL_EXTENSIONS.
106
108 GL_INVALID_ENUM is generated if target is not GL_CONVOLUTION_2D.
109 GL_INVALID_ENUM is generated if internalformat is not one of the
111 allowable values.
112 GL_INVALID_VALUE is generated if width is less than zero or greater
114 than the maximum supported value. This value may be queried with
115 glGetConvolutionParameter() using target GL_CONVOLUTION_2D and name
116 GL_MAX_CONVOLUTION_WIDTH.
117 GL_INVALID_VALUE is generated if height is less than zero or greater
119 than the maximum supported value. This value may be queried with
120 glGetConvolutionParameter() using target GL_CONVOLUTION_2D and name
121 GL_MAX_CONVOLUTION_HEIGHT.
122 GL_INVALID_OPERATION is generated if glCopyConvolutionFilter2D is
124 executed between the execution of glBegin() and the corresponding
125 execution of glEnd().
126
128 glGetConvolutionParameter(), glGetConvolutionFilter()
129
131 glConvolutionFilter2D(), glConvolutionParameter(), glPixelTransfer()
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134 Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
135 under the SGI Free Software B License. For details, see
136 http://oss.sgi.com/projects/FreeB/.
137
139 opengl.org
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