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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2024, Red Hat Inc.
*
* Auto white balance
*/
#include "awb.h"
#include <numeric>
#include <stdint.h>
#include <libcamera/base/log.h>
#include "simple/ipa_context.h"
namespace libcamera {
LOG_DEFINE_CATEGORY(IPASoftAwb)
namespace ipa::soft::algorithms {
int Awb::configure(IPAContext &context,
[[maybe_unused]] const IPAConfigInfo &configInfo)
{
auto &gains = context.activeState.gains;
gains.red = gains.green = gains.blue = 256;
return 0;
}
void Awb::process(IPAContext &context,
[[maybe_unused]] const uint32_t frame,
[[maybe_unused]] IPAFrameContext &frameContext,
const SwIspStats *stats,
[[maybe_unused]] ControlList &metadata)
{
const SwIspStats::Histogram &histogram = stats->yHistogram;
const uint8_t blackLevel = context.activeState.blc.level;
/*
* Black level must be subtracted to get the correct AWB ratios, they
* would be off if they were computed from the whole brightness range
* rather than from the sensor range.
*/
const uint64_t nPixels = std::accumulate(
histogram.begin(), histogram.end(), 0);
const uint64_t offset = blackLevel * nPixels;
const uint64_t sumR = stats->sumR_ - offset / 4;
const uint64_t sumG = stats->sumG_ - offset / 2;
const uint64_t sumB = stats->sumB_ - offset / 4;
/*
* Calculate red and blue gains for AWB.
* Clamp max gain at 4.0, this also avoids 0 division.
* Gain: 128 = 0.5, 256 = 1.0, 512 = 2.0, etc.
*/
auto &gains = context.activeState.gains;
gains.red = sumR <= sumG / 4 ? 1024 : 256 * sumG / sumR;
gains.blue = sumB <= sumG / 4 ? 1024 : 256 * sumG / sumB;
/* Green gain is fixed to 256 */
LOG(IPASoftAwb, Debug) << "gain R/B " << gains.red << "/" << gains.blue;
}
REGISTER_IPA_ALGORITHM(Awb, "Awb")
} /* namespace ipa::soft::algorithms */
} /* namespace libcamera */
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