libcamera/pinchartl/libcamera.git - Laurent Pinchart's clone of libcamera

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author	Milan Zamazal <mzamazal@redhat.com>	2024-04-16 11:13:54 +0200
committer	Kieran Bingham <kieran.bingham@ideasonboard.com>	2024-04-16 13:00:21 +0100
commit	b2ef255295871fb6246d99bdd5b41aa65e3fc3b2 (patch)
tree	de44bd747447b765408df07ee0c037fb10e761f3 /src/libcamera/converter/meson.build
parent	d9b2619e2e9a2c7d5a74330229ae8f897e06b951 (diff)

libcamera: software_isp: Apply black level compensation

Black may not be represented as 0 pixel value for given hardware, it may be higher. If this is not compensated then various problems may occur such as low contrast or suboptimal exposure. The black pixel value can be either retrieved from a tuning file for the given hardware, or automatically on the fly. The former is the right and correct method, while the latter can be used when a tuning file is not available for the given hardware. Since there is currently no support for tuning files in software ISP, the automatic, hardware independent way, is always used. Support for tuning files should be added in future but it will require more work than this patch. The patch looks at the image histogram and assumes that black starts when pixel values start occurring on the left. A certain amount of the darkest pixels is ignored; it doesn't matter whether they represent various kinds of noise or are real, they are better to omit in any case to make the image looking better. It also doesn't matter whether the darkest pixels occur around the supposed black level or are spread between 0 and the black level, the difference is not important. An arbitrary threshold of 2% darkest pixels is applied; there is no magic about that value. The patch assumes that the black values for different colors are the same and doesn't attempt any other non-primitive enhancements. It cannot completely replace tuning files and simplicity, while providing visible benefit, is its goal. Anything more sophisticated is left for future patches. A possible cheap enhancement, if needed, could be setting exposure + gain to minimum values temporarily, before setting the black level. In theory, the black level should be fixed but it may not be reached in all images. For this reason, the patch updates black level only if the observed value is lower than the current one; it should be never increased. The purpose of the patch is to compensate for hardware properties. General image contrast enhancements are out of scope of this patch. Stats are still gathered as an uncorrected histogram, to avoid any confusion and to represent the raw image data. Exposure must be determined after the black level correction -- it has no influence on the sub-black area and must be correct after applying the black level correction. The granularity of the histogram is increased from 16 to 64 to provide a better precision (there is no theory behind either of those numbers). Reviewed-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Milan Zamazal <mzamazal@redhat.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Milan Zamazal <mzamazal@redhat.com> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

Diffstat (limited to 'src/libcamera/converter/meson.build')

0 files changed, 0 insertions, 0 deletions

/* SPDX-License-Identifier: GPL-2.0-or-later */ /* * Copyright (C) 2018, Google Inc. * * utils.cpp - Miscellaneous utility tests */ #include <iostream> #include <map> #include <sstream> #include <string> #include <vector> #include <libcamera/base/span.h> #include <libcamera/base/utils.h> #include <libcamera/geometry.h> #include "test.h" using namespace std; using namespace libcamera; using namespace std::literals::chrono_literals; class UtilsTest : public Test { protected: int testDirname() { static const std::vector<std::string> paths = { "", "///", "/bin", "/usr/bin", "//etc////", "//tmp//d//", "current_file", "./current_file", "./current_dir/", "current_dir/", }; static const std::vector<std::string> expected = { ".", "/", "/", "/usr", "/", "//tmp", ".", ".", ".", ".", }; std::vector<std::string> results; for (const auto &path : paths) results.push_back(utils::dirname(path)); if (results != expected) { cerr << "utils::dirname() tests failed" << endl; cerr << "expected: " << endl; for (const auto &path : expected) cerr << "\t" << path << endl; cerr << "results: " << endl; for (const auto &path : results) cerr << "\t" << path << endl; return TestFail; } return TestPass; } int testEnumerate() { std::vector<unsigned int> integers{ 1, 2, 3, 4, 5 }; unsigned int i = 0; for (auto [index, value] : utils::enumerate(integers)) { if (index != i || value != i + 1) { cerr << "utils::enumerate(<vector>) test failed: i=" << i << ", index=" << index << ", value=" << value << std::endl; return TestFail; } /* Verify that we can modify the value. */ --value; ++i; } if (integers != std::vector<unsigned int>{ 0, 1, 2, 3, 4 }) { cerr << "Failed to modify container in enumerated range loop" << endl; return TestFail; } Span<const unsigned int> span{ integers }; i = 0; for (auto [index, value] : utils::enumerate(span)) { if (index != i || value != i) { cerr << "utils::enumerate(<span>) test failed: i=" << i << ", index=" << index << ", value=" << value << std::endl; return TestFail; } ++i; } const unsigned int array[] = { 0, 2, 4, 6, 8 }; i = 0; for (auto [index, value] : utils::enumerate(array)) { if (index != i || value != i * 2) { cerr << "utils::enumerate(<array>) test failed: i=" << i << ", index=" << index << ", value=" << value << std::endl; return TestFail; } ++i; } return TestPass; } int testDuration() { std::ostringstream os; utils::Duration exposure; double ratio; exposure = 25ms + 25ms; if (exposure.get<std::micro>() != 50000.0) { cerr << "utils::Duration failed to return microsecond count"; return TestFail; } exposure = 1.0s / 4; if (exposure != 250ms) { cerr << "utils::Duration failed scalar divide test"; return TestFail; } exposure = 5000.5us; if (!exposure) { cerr << "utils::Duration failed boolean test"; return TestFail; } os << exposure; if (os.str() != "5000.50us") { cerr << "utils::Duration operator << failed"; return TestFail; } exposure = 100ms; ratio = exposure / 25ms; if (ratio != 4.0) { cerr << "utils::Duration failed ratio test"; return TestFail; } return TestPass; } int run() { /* utils::hex() test. */ std::ostringstream os; std::string ref; os << utils::hex(static_cast<int32_t>(0x42)) << " "; ref += "0x00000042 "; os << utils::hex(static_cast<uint32_t>(0x42)) << " "; ref += "0x00000042 "; os << utils::hex(static_cast<int64_t>(0x42)) << " "; ref += "0x0000000000000042 "; os << utils::hex(static_cast<uint64_t>(0x42)) << " "; ref += "0x0000000000000042 "; os << utils::hex(static_cast<int32_t>(0x42), 4) << " "; ref += "0x0042 "; os << utils::hex(static_cast<uint32_t>(0x42), 1) << " "; ref += "0x42 "; os << utils::hex(static_cast<int64_t>(0x42), 4) << " "; ref += "0x0042 "; os << utils::hex(static_cast<uint64_t>(0x42), 1) << " "; ref += "0x42 "; std::string s = os.str(); if (s != ref) { cerr << "utils::hex() test failed, expected '" << ref << "', got '" << s << "'"; return TestFail; } /* utils::join() and utils::split() test. */ std::vector<std::string> elements = { "/bin", "/usr/bin", "", "", }; std::string path; for (const auto &element : elements) path += (path.empty() ? "" : ":") + element; if (path != utils::join(elements, ":")) { cerr << "utils::join() test failed" << endl; return TestFail; } std::vector<std::string> dirs; for (const auto &dir : utils::split(path, ":")) dirs.push_back(dir); if (dirs != elements) { cerr << "utils::split() test failed" << endl; return TestFail; } /* utils::join() with conversion function test. */ std::vector<Size> sizes = { { 0, 0 }, { 100, 100 } }; s = utils::join(sizes, "/", [](const Size &size) { return size.toString(); }); if (s != "0x0/100x100") { cerr << "utils::join() with conversion test failed" << endl; return TestFail; } /* utils::dirname() tests. */ if (TestPass != testDirname()) return TestFail; /* utils::map_keys() test. */ const std::map<std::string, unsigned int> map{ { "zero", 0 }, { "one", 1 }, { "two", 2 }, }; std::vector<std::string> expectedKeys{ "zero", "one", "two", }; std::sort(expectedKeys.begin(), expectedKeys.end()); const std::vector<std::string> keys = utils::map_keys(map); if (keys != expectedKeys) { cerr << "utils::map_keys() test failed" << endl; return TestFail; } /* utils::alignUp() and utils::alignDown() tests. */ if (utils::alignDown(6, 3) != 6 || utils::alignDown(7, 3) != 6) { cerr << "utils::alignDown test failed" << endl; return TestFail; } if (utils::alignUp(6, 3) != 6 || utils::alignUp(7, 3) != 9) { cerr << "utils::alignUp test failed" << endl; return TestFail; } /* utils::enumerate() test. */ if (testEnumerate() != TestPass) return TestFail; /* utils::Duration test. */ if (testDuration() != TestPass) return TestFail; return TestPass; } }; TEST_REGISTER(UtilsTest)


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