1GLCOLORTABLE(3G) GLCOLORTABLE(3G)
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6 glColorTable - define a color lookup table
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10 void glColorTable( GLenum target,
11 GLenum internalformat,
12 GLsizei width,
13 GLenum format,
14 GLenum type,
15 const GLvoid *table )
16
19 target Must be one of GL_COLOR_TABLE,
20 GL_POST_CONVOLUTION_COLOR_TABLE,
21 GL_POST_COLOR_MATRIX_COLOR_TABLE, GL_PROXY_COLOR_TABLE,
22 GL_PROXY_POST_CONVOLUTION_COLOR_TABLE, or
23 GL_PROXY_POST_COLOR_MATRIX_COLOR_TABLE.
24 internalformat The internal of the color table. The allowable values
26 are GL_ALPHA, GL_ALPHA4, GL_ALPHA8, GL_ALPHA12,
27 GL_ALPHA16, GL_LUMINANCE, GL_LUMINANCE4, GL_LUMINANCE8,
28 GL_LUMINANCE12, GL_LUMINANCE16, GL_LUMINANCE_ALPHA,
29 GL_LUMINANCE4_ALPHA4, GL_LUMINANCE6_ALPHA2,
30 GL_LUMINANCE8_ALPHA8, GL_LUMINANCE12_ALPHA4,
31 GL_LUMINANCE12_ALPHA12, GL_LUMINANCE16_ALPHA16,
32 GL_INTENSITY, GL_INTENSITY4, GL_INTENSITY8,
33 GL_INTENSITY12, GL_INTENSITY16, GL_R3_G3_B2, GL_RGB,
34 GL_RGB4, GL_RGB5, GL_RGB8, GL_RGB10, GL_RGB12,
35 GL_RGB16, GL_RGBA, GL_RGBA2, GL_RGBA4, GL_RGB5_A1,
36 GL_RGBA8, GL_RGB10_A2, GL_RGBA12, and GL_RGBA16.
37 width The number of entries in the color lookup table speci‐
39 fied by table.
40 format The of the pixel data in table. The allowable values
42 are GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_LUMINANCE,
43 GL_LUMINANCE_ALPHA, GL_RGB, GL_BGR, GL_RGBA, and
44 GL_BGRA.
45 type The type of the pixel data in table. The allowable
47 values are GL_UNSIGNED_BYTE, GL_BYTE,
48 GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT, GL_INT,
49 GL_FLOAT, GL_UNSIGNED_BYTE_3_3_2,
50 GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5,
51 GL_UNSIGNED_SHORT_5_6_5_REV, GL_UNSIGNED_SHORT_4_4_4_4,
52 GL_UNSIGNED_SHORT_4_4_4_4_REV,
53 GL_UNSIGNED_SHORT_5_5_5_1,
54 GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8,
55 GL_UNSIGNED_INT_8_8_8_8_REV,
56 GL_UNSIGNED_INT_10_10_10_2, and
57 GL_UNSIGNED_INT_2_10_10_10_REV.
58 table Pointer to a one-dimensional array of pixel data that
60 is processed to build the color table.
61
63 glColorTable may be used in two ways: to test the actual size and color
64 resolution of a lookup table given a particular set of parameters, or
65 to load the contents of a color lookup table. Use the targets
66 GL_PROXY_* for the first case and the other targets for the second
67 case.
68 If target is GL_COLOR_TABLE, GL_POST_CONVOLUTION_COLOR_TABLE, or
70 GL_POST_COLOR_MATRIX_COLOR_TABLE, glColorTable builds a color lookup
71 table from an array of pixels. The pixel array specified by width,
72 format, type, and table is extracted from memory and processed just as
73 if glDrawPixels were called, but processing stops after the final
74 expansion to RGBA is completed.
75 The four scale parameters and the four bias parameters that are defined
77 for the table are then used to scale and bias the R, G, B, and A compo‐
78 nents of each pixel. (Use glColorTableParameter to set these scale and
79 bias parameters.)
80 Next, the R, G, B, and A values are clamped to the range [0, 1]. Each
82 pixel is then converted to the internal specified by internalformat.
83 This conversion simply maps the component values of the pixel (R, G, B,
84 and A) to the values included in the internal (red, green, blue,
85 alpha, luminance, and intensity). The mapping is as follows:
86 ────────────────────────────────────────────────────────────────────────
88 Internal Format Red Green Blue Alpha Luminance Intensity
89 ────────────────────────────────────────────────────────────────────────
90 GL_ALPHA A
91 GL_LUMINANCE R
92 GL_LUMINANCE_ALPHA A R
93 GL_INTENSITY R
94 GL_RGB R G B
95 GL_RGBA R G B A
96 ────────────────────────────────────────────────────────────────────────
97 Finally, the red, green, blue, alpha, luminance, and/or intensity com‐
99 ponents of the resulting pixels are stored in the color table. They
100 form a one-dimensional table with indices in the range [0, width - 1].
101 If target is GL_PROXY_*, glColorTable recomputes and stores the values
103 of the proxy color table's state variables GL_COLOR_TABLE_FORMAT,
104 GL_COLOR_TABLE_WIDTH, GL_COLOR_TABLE_RED_SIZE,
105 GL_COLOR_TABLE_GREEN_SIZE, GL_COLOR_TABLE_BLUE_SIZE,
106 GL_COLOR_TABLE_ALPHA_SIZE, GL_COLOR_TABLE_LUMINANCE_SIZE, and
107 GL_COLOR_TABLE_INTENSITY_SIZE. There is no effect on the image or
108 state of any actual color table. If the specified color table is too
109 large to be supported, then all the proxy state variables listed above
110 are set to zero. Otherwise, the color table could be supported by
111 glColorTable using the corresponding non-proxy target, and the proxy
112 state variables are set as if that target were being defined.
113 The proxy state variables can be retrieved by calling
115 glGetColorTableParameter with a target of GL_PROXY_*. This allows the
116 application to decide if a particular glColorTable command would suc‐
117 ceed, and to determine what the resulting color table attributes would
118 be.
119 If a color table is enabled, and its width is non-zero, then its con‐
121 tents are used to replace a subset of the components of each RGBA pixel
122 group, based on the internal of the table.
123 Each pixel group has color components (R, G, B, A) that are in the
125 range [0.0, 1.0]. The color components are rescaled to the size of the
126 color lookup table to form an index. Then a subset of the components
127 based on the internal of the table are replaced by the table entry
128 selected by that index. If the color components and contents of the
129 table are represented as follows:
130 ──────────────────────────────────────────────────
132 Representation Meaning
133 ──────────────────────────────────────────────────
134 r Table index computed from R
135 g Table index computed from G
136 b Table index computed from B
137 a Table index computed from A
138 L[i] Luminance value at table index i
139 I[i] Intensity value at table index i
140 R[i] Red value at table index i
141 G[i] Green value at table index i
142 B[i] Blue value at table index i
143 A[i] Alpha value at table index i
144 ──────────────────────────────────────────────────
145 then the result of color table lookup is as follows:
147 ─────────────────────────────────────────────────────
149 Resulting Texture Components
150 Table Internal Format R G B A
151 ─────────────────────────────────────────────────────
152 GL_ALPHA R G B A[a]
153 GL_LUMINANCE L[r] L[g] L[b] At
154 GL_LUMINANCE_ALPHA L[r] L[g] L[b] A[a]
155 GL_INTENSITY I[r] I[g] I[b] I[a]
156 GL_RGB R[r] G[g] B[b] A
157 GL_RGBA R[r] G[g] B[b] A[a]
158 ─────────────────────────────────────────────────────
159 When GL_COLOR_TABLE is enabled, the colors resulting from the pixel map
161 operation (if it is enabled) are mapped by the color lookup table
162 before being passed to the convolution operation. The colors resulting
163 from the convolution operation are modified by the post convolution
164 color lookup table when GL_POST_CONVOLUTION_COLOR_TABLE is enabled.
165 These modified colors are then sent to the color matrix operation.
166 Finally, if GL_POST_COLOR_MATRIX_COLOR_TABLE is enabled, the colors
167 resulting from the color matrix operation are mapped by the post color
168 matrix color lookup table before being used by the histogram operation.
169
171 glColorTable is present only if GL_ARB_imaging is returned when
172 glGetString is called with an argument of GL_EXTENSIONS.
173 If target is set to GL_COLOR_TABLE, GL_POST_CONVOLUTION_COLOR_TABLE, or
175 GL_POST_COLOR_MATRIX_COLOR_TABLE, then width must be a power of two or
176 a GL_INVALID_VALUE error is generated.
177
179 GL_INVALID_ENUM is generated if target is not one of the allowable val‐
180 ues.
181 GL_INVALID_ENUM is generated if internalformat is not one of the allow‐
183 able values.
184 GL_INVALID_VALUE is generated if width is less than zero.
186 GL_INVALID_ENUM is generated if format is not one of the allowable val‐
188 ues.
189 GL_INVALID_ENUM is generated if type is not one of the allowable val‐
191 ues.
192 GL_TABLE_TOO_LARGE is generated if the requested color table is too
194 large to be supported by the implementation, and target is not a
195 GL_PROXY_* target.
196 GL_INVALID_OPERATION is generated if glColorTable is executed between
198 the execution of glBegin and the corresponding execution of glEnd.
199
201 glGetColorTableParameter
202
204 glColorSubTable(3G), glColorTableParameter(3G), glCopyColorTable(3G),
205 glCopyColorSubTable(3G), glGetColorTable(3G)
206 GLCOLORTABLE(3G)