diff options
| author | David Plowman <david.plowman@raspberrypi.com> | 2020-11-23 07:38:03 +0000 |
|---|---|---|
| committer | Kieran Bingham <kieran.bingham@ideasonboard.com> | 2020-11-23 14:24:45 +0000 |
| commit | 7de5506c30b36575de7bbead7fda243ec1019005 (patch) | |
| tree | 58886fe65956fb26ae80f6ecbd21a53dba43c62e | |
| parent | 393f05a9a8044dba26251ba5a4b0827b714cd15f (diff) | |
libcamera: src: ipa: raspberrypi: agc: Improve gain update calculation for partly saturated images
When parts of an image saturate then the image brightness no longer
increases linearly with increased exposure/gain. Having calculated a
linear gain value it's better then to try it, allowing for saturating
regions, and if necessary increase the gain some more. We repeat this
several times.
Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
| -rw-r--r-- | src/ipa/raspberrypi/controller/rpi/agc.cpp | 34 |
1 files changed, 24 insertions, 10 deletions
diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp b/src/ipa/raspberrypi/controller/rpi/agc.cpp index d7d37055..37806055 100644 --- a/src/ipa/raspberrypi/controller/rpi/agc.cpp +++ b/src/ipa/raspberrypi/controller/rpi/agc.cpp @@ -419,17 +419,21 @@ void Agc::fetchAwbStatus(Metadata *image_metadata) } static double compute_initial_Y(bcm2835_isp_stats *stats, AwbStatus const &awb, - double weights[]) + double weights[], double gain) { bcm2835_isp_stats_region *regions = stats->agc_stats; // Note how the calculation below means that equal weights give you // "average" metering (i.e. all pixels equally important). double R_sum = 0, G_sum = 0, B_sum = 0, pixel_sum = 0; for (int i = 0; i < AGC_STATS_SIZE; i++) { - R_sum += regions[i].r_sum * weights[i]; - G_sum += regions[i].g_sum * weights[i]; - B_sum += regions[i].b_sum * weights[i]; - pixel_sum += regions[i].counted * weights[i]; + double counted = regions[i].counted; + double r_sum = std::min(regions[i].r_sum * gain, ((1 << PIPELINE_BITS) - 1) * counted); + double g_sum = std::min(regions[i].g_sum * gain, ((1 << PIPELINE_BITS) - 1) * counted); + double b_sum = std::min(regions[i].b_sum * gain, ((1 << PIPELINE_BITS) - 1) * counted); + R_sum += r_sum * weights[i]; + G_sum += g_sum * weights[i]; + B_sum += b_sum * weights[i]; + pixel_sum += counted * weights[i]; } if (pixel_sum == 0.0) { LOG(RPiAgc, Warning) << "compute_initial_Y: pixel_sum is zero"; @@ -473,11 +477,21 @@ void Agc::computeGain(bcm2835_isp_stats *statistics, Metadata *image_metadata, target_Y = config_.Y_target.Eval(config_.Y_target.Domain().Clip(lux.lux)); target_Y = std::min(EV_GAIN_Y_TARGET_LIMIT, target_Y * ev_gain); - double initial_Y = compute_initial_Y(statistics, awb_, - metering_mode_->weights); - gain = std::min(10.0, target_Y / (initial_Y + .001)); - LOG(RPiAgc, Debug) << "Initially Y " << initial_Y << " target " << target_Y - << " gives gain " << gain; + + // Do this calculation a few times as brightness increase can be + // non-linear when there are saturated regions. + gain = 1.0; + for (int i = 0; i < 8; i++) { + double initial_Y = compute_initial_Y(statistics, awb_, + metering_mode_->weights, gain); + double extra_gain = std::min(10.0, target_Y / (initial_Y + .001)); + gain *= extra_gain; + LOG(RPiAgc, Debug) << "Initial Y " << initial_Y << " target " << target_Y + << " gives gain " << gain; + if (extra_gain < 1.01) // close enough + break; + } + for (auto &c : *constraint_mode_) { double new_target_Y; double new_gain = |