135 lines
4 KiB
C
135 lines
4 KiB
C
#include <stdio.h>
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#include <stdint.h>
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#include <math.h>
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/* gpsp targets devices that are too slow to generate
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* a colour correction table at runtime. We therefore
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* have to pre-generate the lookup table array... */
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/* Colour correction defines */
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#define CC_TARGET_GAMMA 2.2f
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#define CC_RGB_MAX 31.0f
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#define CC_LUM 0.94f
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#define CC_R 0.82f
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#define CC_G 0.665f
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#define CC_B 0.73f
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#define CC_RG 0.125f
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#define CC_RB 0.195f
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#define CC_GR 0.24f
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#define CC_GB 0.075f
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#define CC_BR -0.06f
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#define CC_BG 0.21f
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#define CC_GAMMA_ADJ 1.0f
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/* Output video is RGB565. This is 16bit,
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* but only 15 bits are actually used
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* (i.e. 'G' is the highest 5 bits of the
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* 6bit component). To save memory, we
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* only include 15bit compound values
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* and convert RGB565 video to 15bit when
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* using the lookup table */
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#define CC_LUT_SIZE 32768
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static uint16_t c_lut[CC_LUT_SIZE] = {0};
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void init_lut(void)
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{
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size_t color;
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float display_gamma_inv = 1.0f / CC_TARGET_GAMMA;
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float rgb_max_inv = 1.0f / CC_RGB_MAX;
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float adjusted_gamma = CC_TARGET_GAMMA + CC_GAMMA_ADJ;
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/* Populate colour correction look-up table */
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for (color = 0; color < CC_LUT_SIZE; color++)
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{
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unsigned r_final = 0;
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unsigned g_final = 0;
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unsigned b_final = 0;
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/* Extract values from RGB555 input */
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const unsigned r = color >> 10 & 0x1F;
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const unsigned g = color >> 5 & 0x1F;
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const unsigned b = color & 0x1F;
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/* Perform gamma expansion */
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float r_float = pow((float)r * rgb_max_inv, adjusted_gamma);
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float g_float = pow((float)g * rgb_max_inv, adjusted_gamma);
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float b_float = pow((float)b * rgb_max_inv, adjusted_gamma);
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/* Perform colour mangling */
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float r_correct = CC_LUM * ((CC_R * r_float) + (CC_GR * g_float) + (CC_BR * b_float));
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float g_correct = CC_LUM * ((CC_RG * r_float) + (CC_G * g_float) + (CC_BG * b_float));
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float b_correct = CC_LUM * ((CC_RB * r_float) + (CC_GB * g_float) + (CC_B * b_float));
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/* Range check... */
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r_correct = r_correct > 0.0f ? r_correct : 0.0f;
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g_correct = g_correct > 0.0f ? g_correct : 0.0f;
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b_correct = b_correct > 0.0f ? b_correct : 0.0f;
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/* Perform gamma compression */
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r_correct = pow(r_correct, display_gamma_inv);
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g_correct = pow(g_correct, display_gamma_inv);
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b_correct = pow(b_correct, display_gamma_inv);
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/* Range check... */
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r_correct = r_correct > 1.0f ? 1.0f : r_correct;
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g_correct = g_correct > 1.0f ? 1.0f : g_correct;
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b_correct = b_correct > 1.0f ? 1.0f : b_correct;
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/* Convert to RGB565 */
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r_final = (unsigned)((r_correct * CC_RGB_MAX) + 0.5f) & 0x1F;
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g_final = (unsigned)((g_correct * CC_RGB_MAX) + 0.5f) & 0x1F;
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b_final = (unsigned)((b_correct * CC_RGB_MAX) + 0.5f) & 0x1F;
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c_lut[color] = r_final << 11 | g_final << 6 | b_final;
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}
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}
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int main(int argc, char *argv[])
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{
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FILE *file = NULL;
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size_t i;
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/* Populate lookup table */
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init_lut();
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/* Write header file */
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file = fopen("../gba_cc_lut.h", "w");
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if (!file)
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return 1;
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fprintf(file,
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"#ifndef __CC_LUT_H__\n"
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"#define __CC_LUT_H__\n\n"
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"#include \"common.h\"\n\n"
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"extern const u16 gba_cc_lut[];\n\n"
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"#endif /* __CC_LUT_H__ */\n");
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fclose(file);
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file = NULL;
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/* Write source file */
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file = fopen("../gba_cc_lut.c", "w");
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if (!file)
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return 1;
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fprintf(file,
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"#include \"gba_cc_lut.h\"\n\n"
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"const u16 gba_cc_lut[] = {\n");
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for (i = 0; i < CC_LUT_SIZE; i++)
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{
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fprintf(file, " 0x%04x", c_lut[i]);
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if (i == CC_LUT_SIZE - 1)
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fprintf(file, "\n");
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else
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{
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if ((i + 1) % 5 == 0)
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fprintf(file, ",\n");
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else
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fprintf(file, ",");
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}
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}
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fprintf(file, "};\n");
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fclose(file);
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file = NULL;
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return 0;
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}
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