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| -rw-r--r-- | src/gamma.c | 72 | ||||
| -rw-r--r-- | src/gamma.h | 52 |
2 files changed, 124 insertions, 0 deletions
diff --git a/src/gamma.c b/src/gamma.c new file mode 100644 index 0000000..fa57fb4 --- /dev/null +++ b/src/gamma.c @@ -0,0 +1,72 @@ +/** + * crt-calibrator – Calibration utility for CRT monitors + * Copyright © 2014 Mattias Andrée (maandree@member.fsf.org) + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + */ +#include "gamma.h" + +#include <math.h> + + +/** + * Analyse a gamma ramp + * + * @param stops The number of stops in the gamma ramp + * @param ramp The gamma ramp + * @param gamma Output parameter for the gamma + * @param contrast Output parameter for the contrast + * @param brightness Output parameter for the brightness + */ +void gamma_analyse(size_t stops, const uint16_t* restrict ramp, double* restrict gamma, + double* restrict contrast, double* restrict brightness) +{ + double min, middle, max; + *brightness = min = (double)(ramp[0]) / (double)0xFFFF; + *contrast = max = (double)(ramp[stops - 1]) / (double)0xFFFF; + middle = (double)(ramp[stops / 2]) / (double)0xFFFF; + + middle = (middle - min) / (max - min); + *gamma = log(middle) / log(2.0); +} + + +/** + * Generate a gamma ramp + * + * @param stops The number of stops in the gamma ramp + * @param ramp Memory area to where to write the gamma ramp + * @param gamma The gamma + * @param contrast The contrast + * @param brightness The brightness + */ +void gamma_generate(size_t stops, uint16_t* restrict ramp, double gamma, + double contrast, double brightness) +{ + double diff = contrast - brightness; + size_t i; + int32_t y; + double y_; + + for (i = 0; i < stops; i++) + { + y_ = (double)i / (double)stops; + y_ = pow(y_, gamma) * diff + brightness; + y = (int32_t)(y * 0xFFFF); + if (y < 0x0000) y = 0x0000; + if (y > 0xFFFF) y = 0xFFFF; + ramp[i] = y; + } +} + diff --git a/src/gamma.h b/src/gamma.h new file mode 100644 index 0000000..9652598 --- /dev/null +++ b/src/gamma.h @@ -0,0 +1,52 @@ +/** + * crt-calibrator – Calibration utility for CRT monitors + * Copyright © 2014 Mattias Andrée (maandree@member.fsf.org) + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + */ +#ifndef CRT_CALIBRATOR_GAMMA_H +#define CRT_CALIBRATOR_GAMMA_H + + +#include <stddef.h> +#include <stdint.h> + + +/** + * Analyse a gamma ramp + * + * @param stops The number of stops in the gamma ramp + * @param ramp The gamma ramp + * @param gamma Output parameter for the gamma + * @param contrast Output parameter for the contrast + * @param brightness Output parameter for the brightness + */ +void gamma_analyse(size_t stops, const uint16_t* restrict ramp, double* restrict gamma, + double* restrict contrast, double* restrict brightness); + +/** + * Generate a gamma ramp + * + * @param stops The number of stops in the gamma ramp + * @param ramp Memory area to where to write the gamma ramp + * @param gamma The gamma + * @param contrast The contrast + * @param brightness The brightness + */ +void gamma_generate(size_t stops, uint16_t* restrict ramp, double gamma, + double contrast, double brightness); + + +#endif + |