/* SPDX-License-Identifier: BSD-2-Clause */ /* * Copyright (C) 2019, Raspberry Pi Ltd * * histogram calculations */ #include "histogram.h" #include #include /** * \file histogram.h * \brief Class to represent Histograms and manipulate them */ namespace libcamera { namespace ipa { /** * \class Histogram * \brief The base class for creating histograms * * This class stores a cumulative frequency histogram, which is a mapping that * counts the cumulative number of observations in all of the bins up to the * specified bin. It can be used to find quantiles and averages between quantiles. */ /** * \fn Histogram::Histogram() * \brief Construct an empty Histogram * * This empty constructor exists largely to allow Histograms to be embedded in * other classes which may be created before the contents of the Histogram are * known. */ /** * \brief Create a cumulative histogram * \param[in] data A (non-cumulative) histogram */ Histogram::Histogram(Span data) { cumulative_.resize(data.size() + 1); cumulative_[0] = 0; for (const auto &[i, value] : utils::enumerate(data)) cumulative_[i + 1] = cumulative_[i] + value; } /** * \fn Histogram::Histogram(Span data, Transform transform) * \brief Create a cumulative histogram * \param[in] data A (non-cumulative) histogram * \param[in] transform The transformation function to apply to every bin */ /** * \fn Histogram::bins() * \brief Retrieve the number of bins currently used by the Histogram * \return Number of bins */ /** * \fn Histogram::data() * \brief Retrieve the internal data * \return The data */ /** * \fn Histogram::total() * \brief Retrieve the total number of values in the data set * \return Number of values */ /** * \brief Cumulative frequency up to a (fractional) point in a bin * \param[in] bin The bin up to which to cumulate * * With F(p) the cumulative frequency of the histogram, the value is 0 at * the bottom of the histogram, and the maximum is the number of bins. * The pixels are spread evenly throughout the “bin” in which they lie, so that * F(p) is a continuous (monotonically increasing) function. * * \return The cumulative frequency from 0 up to the specified bin */ uint64_t Histogram::cumulativeFrequency(double bin) const { if (bin <= 0) return 0; else if (bin >= bins()) return total(); int b = static_cast(bin); return cumulative_[b] + (bin - b) * (cumulative_[b + 1] - cumulative_[b]); } /** * \brief Return the (fractional) bin of the point through the histogram * \param[in] q the desired point (0 <= q <= 1) * \param[in] first low limit (default is 0) * \param[in] last high limit (default is UINT_MAX) * * A quantile gives us the point p = Q(q) in the range such that a proportion * q of the pixels lie below p. A familiar quantile is Q(0.5) which is the median * of a distribution. * * \return The fractional bin of the point */ double Histogram::quantile(double q, uint32_t first, uint32_t last) const { if (last == UINT_MAX) last = cumulative_.size() - 2; ASSERT(first <= last); uint64_t item = q * total(); /* Binary search to find the right bin */ while (first < last) { int middle = (first + last) / 2; /* Is it between first and middle ? */ if (cumulative_[middle + 1] > item) last = middle; else first = middle + 1; } ASSERT(item >= cumulative_[first] && item <= cumulative_[last + 1]); double frac; if (cumulative_[first + 1] == cumulative_[first]) frac = 0; else frac = (item - cumulative_[first]) / (cumulative_[first + 1] - cumulative_[first]); return first + frac; } /** * \brief Calculate the mean between two quantiles * \param[in] lowQuantile low Quantile * \param[in] highQuantile high Quantile * * Quantiles are not ideal for metering as they suffer several limitations. * Instead, a concept is introduced here: inter-quantile mean. * It returns the mean of all pixels between lowQuantile and highQuantile. * * \return The mean histogram bin value between the two quantiles */ double Histogram::interQuantileMean(double lowQuantile, double highQuantile) const { ASSERT(highQuantile > lowQuantile); /* Proportion of pixels which lies below lowQuantile */ double lowPoint = quantile(lowQuantile); /* Proportion of pixels which lies below highQuantile */ double highPoint = quantile(highQuantile, static_cast(lowPoint)); double sumBinFreq = 0, cumulFreq = 0; for (double p_next = floor(lowPoint) + 1.0; p_next <= ceil(highPoint); lowPoint = p_next, p_next += 1.0) { int bin = floor(lowPoint); double freq = (cumulative_[bin + 1] - cumulative_[bin]) * (std::min(p_next, highPoint) - lowPoint); /* Accumulate weighted bin */ sumBinFreq += bin * freq; /* Accumulate weights */ cumulFreq += freq; } /* add 0.5 to give an average for bin mid-points */ return sumBinFreq / cumulFreq + 0.5; } } /* namespace ipa */ } /* namespace libcamera */ ef='#n41'>41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418

/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Google Inc.
 *
 * framebuffer.cpp - Frame buffer handling
 */

#include <libcamera/framebuffer.h>
#include "libcamera/internal/framebuffer.h"

#include <sys/stat.h>

#include <libcamera/base/log.h>
#include <libcamera/base/shared_fd.h>

/**
 * \file libcamera/framebuffer.h
 * \brief Frame buffer handling
 *
 * \file libcamera/internal/framebuffer.h
 * \brief Internal frame buffer handling support
 */

namespace libcamera {

LOG_DEFINE_CATEGORY(Buffer)

/**
 * \struct FrameMetadata
 * \brief Metadata related to a captured frame