diff options
| -rw-r--r-- | src/ipa/libipa/colours.cpp | 77 | ||||
| -rw-r--r-- | src/ipa/libipa/colours.h | 21 | ||||
| -rw-r--r-- | src/ipa/libipa/meson.build | 2 |
3 files changed, 100 insertions, 0 deletions
diff --git a/src/ipa/libipa/colours.cpp b/src/ipa/libipa/colours.cpp new file mode 100644 index 00000000..9fcb53b0 --- /dev/null +++ b/src/ipa/libipa/colours.cpp @@ -0,0 +1,77 @@ +/* SPDX-License-Identifier: BSD-2-Clause */ +/* + * Copyright (C) 2024, Ideas on Board Oy + * + * libipa miscellaneous colour helpers + */ + +#include "colours.h" + +#include <algorithm> +#include <cmath> + +namespace libcamera { + +namespace ipa { + +/** + * \file colours.h + * \brief Functions to reduce code duplication between IPA modules + */ + +/** + * \brief Estimate luminance from RGB values following ITU-R BT.601 + * \param[in] r The red value + * \param[in] g The green value + * \param[in] b The blue value + * + * This function estimates a luminance value from a triplet of Red, Green and + * Blue values, following the formula defined by ITU-R Recommendation BT.601-7 + * which can be found at https://www.itu.int/rec/R-REC-BT.601 + * + * \return The estimated luminance value + */ +double rec601LuminanceFromRGB(double r, double g, double b) +{ + return (r * .299) + (g * .587) + (b * .114); +} + +/** + * \brief Estimate correlated colour temperature from RGB color space input + * \param[in] red The input red value + * \param[in] green The input green value + * \param[in] blue The input blue value + * + * This function estimates the correlated color temperature RGB color space + * input. In physics and color science, the Planckian locus or black body locus + * is the path or locus that the color of an incandescent black body would take + * in a particular chromaticity space as the blackbody temperature changes. + * + * If a narrow range of color temperatures is considered (those encapsulating + * daylight being the most practical case) one can approximate the Planckian + * locus in order to calculate the CCT in terms of chromaticity coordinates. + * + * More detailed information can be found in: + * https://en.wikipedia.org/wiki/Color_temperature#Approximation + * + * \return The estimated color temperature + */ +uint32_t estimateCCT(double red, double green, double blue) +{ + /* Convert the RGB values to CIE tristimulus values (XYZ) */ + double X = (-0.14282) * (red) + (1.54924) * (green) + (-0.95641) * (blue); + double Y = (-0.32466) * (red) + (1.57837) * (green) + (-0.73191) * (blue); + double Z = (-0.68202) * (red) + (0.77073) * (green) + (0.56332) * (blue); + + /* Calculate the normalized chromaticity values */ + double x = X / (X + Y + Z); + double y = Y / (X + Y + Z); + + /* Calculate CCT */ + double n = (x - 0.3320) / (0.1858 - y); + return 449 * n * n * n + 3525 * n * n + 6823.3 * n + 5520.33; +} + +} /* namespace ipa */ + +} /* namespace libcamera */ diff --git a/src/ipa/libipa/colours.h b/src/ipa/libipa/colours.h new file mode 100644 index 00000000..b42ed0ac --- /dev/null +++ b/src/ipa/libipa/colours.h @@ -0,0 +1,21 @@ +/* SPDX-License-Identifier: BSD-2-Clause */ +/* + * Copyright (C) 2024, Ideas on Board Oy + * + * libipa miscellaneous colour helpers + */ + +#pragma once + +#include <stdint.h> + +namespace libcamera { + +namespace ipa { + +double rec601LuminanceFromRGB(double r, double g, double b); +uint32_t estimateCCT(double red, double green, double blue); + +} /* namespace ipa */ + +} /* namespace libcamera */ diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build index e78cbcd6..788d037a 100644 --- a/src/ipa/libipa/meson.build +++ b/src/ipa/libipa/meson.build @@ -4,6 +4,7 @@ libipa_headers = files([ 'agc_mean_luminance.h', 'algorithm.h', 'camera_sensor_helper.h', + 'colours.h', 'exposure_mode_helper.h', 'fc_queue.h', 'histogram.h', @@ -19,6 +20,7 @@ libipa_sources = files([ 'agc_mean_luminance.cpp', 'algorithm.cpp', 'camera_sensor_helper.cpp', + 'colours.cpp', 'exposure_mode_helper.cpp', 'fc_queue.cpp', 'histogram.cpp', |