171 lines
2.4 KiB
C
171 lines
2.4 KiB
C
/*
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* gl_cmap_gen.c
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*
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* OpenGL color map generators
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*
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* Copyright (C) 2013-2021 Sylvain Munaut
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* SPDX-License-Identifier: GPL-3.0-or-later
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*/
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/*! \addtogroup gl/cmap
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* @{
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*/
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/*! \file gl_cmap_gen.c
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* \brief OpenGL color map generators
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*/
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#include <stdint.h>
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#include <math.h>
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#include "gl_cmap_gen.h"
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static void
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_hsv2rgb(float *rgb, float *hsv)
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{
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int i;
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float h, s, v;
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float r, g, b;
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float f, p, q, t;
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/* Unpack input */
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h = hsv[0];
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s = hsv[1];
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v = hsv[2];
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if( s <= 0.0f ) {
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/* achromatic (grey) */
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r = g = b = v;
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goto done;
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}
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h *= 5.0f; /* sector 0 to 5 */
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i = floor(h);
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f = h - i; /* fractional part of h */
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p = v * ( 1 - s );
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q = v * ( 1 - s * f );
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t = v * ( 1 - s * ( 1 - f ) );
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switch (i % 6) {
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case 0:
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r = v;
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g = t;
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b = p;
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break;
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case 1:
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r = q;
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g = v;
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b = p;
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break;
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case 2:
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r = p;
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g = v;
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b = t;
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break;
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case 3:
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r = p;
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g = q;
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b = v;
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break;
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case 4:
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r = t;
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g = p;
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b = v;
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break;
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case 5:
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default:
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r = v;
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g = p;
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b = q;
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break;
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}
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done:
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/* Pack results */
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rgb[0] = r;
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rgb[1] = g;
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rgb[2] = b;
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}
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static void
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_set_rgba_from_rgb(uint32_t *rgba, float r, float g, float b)
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{
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unsigned char rc,gc,bc,ac;
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rc = (unsigned char) roundf(r * 255.0f);
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gc = (unsigned char) roundf(g * 255.0f);
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bc = (unsigned char) roundf(b * 255.0f);
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ac = 255;
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*rgba = (ac << 24) | (bc << 16) | (gc << 8) | rc;
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}
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static void
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_set_rgba_from_hsv(uint32_t *rgba, float h, float s, float v)
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{
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float hsv[3], rgb[3];
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hsv[0] = h;
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hsv[1] = s;
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hsv[2] = v;
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_hsv2rgb(rgb, hsv);
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_set_rgba_from_rgb(rgba, rgb[0], rgb[1], rgb[2]);
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}
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int
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fosphor_gl_cmap_histogram(uint32_t *rgba, int N, void *arg)
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{
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int i;
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int m = N >> 4;
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for (i=0; i<m; i++)
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{
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float p = (1.0f * i) / (N - 1);
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_set_rgba_from_hsv(&rgba[i],
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0.90f, /* H */
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0.50f, /* S */
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0.15f + 4.0f * p /* V */
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);
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}
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for (i=m; i<N; i++)
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{
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float p = (1.0f * i) / (N - 1);
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_set_rgba_from_hsv(&rgba[i],
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0.80f - p * 0.80f,
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1.00f - ((p < 0.85f) ? 0.0f : ((p - 0.85f) * 3.0f)),
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0.60f + ((p < 0.40f) ? p : 0.40f)
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);
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}
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return 0;
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}
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int
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fosphor_gl_cmap_waterfall(uint32_t *rgba, int N, void *arg)
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{
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int i;
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for (i=0; i<N; i++)
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{
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float p = (1.0f * i) / (N - 1);
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_set_rgba_from_hsv(&rgba[i],
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0.75f - (p * 0.75f), /* H */
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1.0f, /* S */
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((p * 0.95f) + 0.05f) /* V */
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);
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}
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return 0;
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}
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/*! @} */
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