| /* |
| * Copyright (C) 2011 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| #define LOG_NDEBUG 0 |
| |
| #define LOG_TAG "WhiteBalanceTest" |
| #include <utils/Log.h> |
| #include <utils/Timers.h> |
| #include <cmath> |
| #include <string> |
| |
| #include "vec2.h" |
| #include "vec3.h" |
| #include "whitebalancetest.h" |
| |
| // White point in XYZ color space under 5200k illumination. |
| const Vec3f kDaylightWhitePoint(0.9781f, 1.f, 0.9021f); |
| |
| // Process the data of checker colors collected under different white balance. |
| // Assuming the Daylight CCT is set to 5200k, compute the CCT of other white |
| // balance modes. |
| void WhiteBalanceTest::processData() { |
| ALOGV("Start Processing White Balance Test Data!"); |
| |
| int numPatches = mCheckerColors.size(); |
| ALOGV("Processing %d tests with %d patches", 2, numPatches); |
| |
| std::vector<Vec3f> xyzColors(numPatches); |
| for (int j = 0; j < numPatches; ++j) { |
| Vec3f xyzCheckerColor = initializeFromRGB(mCheckerColors[j]); |
| xyzColors[j] = xyzCheckerColor; |
| ALOGV("XYZ coordinate is %f, %f, %f", xyzCheckerColor.r(), |
| xyzCheckerColor.g(), xyzCheckerColor.b()); |
| } |
| |
| Vec3f meanScale(0.f, 0.f, 0.f); |
| |
| if (mMode == "daylight") { |
| mXyzColorsDaylight = xyzColors; |
| // For testing the auto white balance mode. Compute a CCT that would |
| // map the gray checkers to a white point. |
| for (int j = 1; j < numPatches; ++j) { |
| meanScale = meanScale + |
| (mXyzColorsDaylight[j] / kDaylightWhitePoint); |
| } |
| } else { |
| for (int j = 1; j < numPatches; ++j) { |
| meanScale = meanScale + (mXyzColorsDaylight[j] / xyzColors[j]); |
| } |
| } |
| |
| meanScale = meanScale / (numPatches - 1); |
| ALOGV("Scale: %f, %f, %f", meanScale.r(), meanScale.g(), meanScale.b()); |
| |
| Vec3f whitePoint; |
| whitePoint = meanScale * kDaylightWhitePoint; |
| |
| ALOGV("White point is %f, %f, %f", whitePoint.r(), |
| whitePoint.g(), whitePoint.b()); |
| |
| mCorrelatedColorTemp = findCorrelatedColorTemp(whitePoint); |
| ALOGV("CCT is %d", mCorrelatedColorTemp); |
| } |
| |
| // Given a white point, find the correlated color temperature. |
| // Formula taken from the paper "Calculating Correlated Color Temperatures |
| // Across the Entire Gamut of Daylight and Skylight Chromaticities" by Hernandez |
| // Andres et al. in 1999. The numbers are fitting parameters. |
| int WhiteBalanceTest::findCorrelatedColorTemp(const Vec3f &whitePoint) { |
| Vec2f chromaOfWhitePoint( |
| whitePoint.r() / (whitePoint.r() + whitePoint.g() + whitePoint.b()), |
| whitePoint.g() / (whitePoint.r() + whitePoint.g() + whitePoint.b())); |
| |
| float n = (chromaOfWhitePoint.x() - 0.3366f) |
| / (chromaOfWhitePoint.y() - 0.1735f); |
| float y = -949.86315f + 6253.80338f * exp(-n / 0.92159f) |
| + 28.70599f * exp(-n / 0.20039f) + 0.00004f * exp(-n / 0.07125f); |
| |
| return static_cast<int>(y); |
| } |
| |
| // Converts a RGB pixel value to XYZ color space. |
| Vec3f WhiteBalanceTest::initializeFromRGB(const Vec3f &rgb) { |
| float linearRed = convertToLinear(rgb.r()); |
| float linearGreen = convertToLinear(rgb.g()); |
| float linearBlue = convertToLinear(rgb.b()); |
| |
| float x = 0.4124f * linearRed + 0.3576f * linearGreen + |
| 0.1805f * linearBlue; |
| float y = 0.2126f * linearRed + 0.7152f * linearGreen + |
| 0.0722f * linearBlue; |
| float z = 0.0193f * linearRed + 0.1192f * linearGreen + |
| 0.9505f * linearBlue; |
| |
| return Vec3f(x, y, z); |
| } |
| |
| float WhiteBalanceTest::convertToLinear(float color) { |
| float norm = color/ 255.0f; |
| float linearColor; |
| |
| // Convert from sRGB space to linear RGB value |
| if (norm > 0.04045f) { |
| linearColor = pow(((norm + 0.055f) / 1.055f), 2.4f); |
| } else { |
| linearColor = norm / 12.92f; |
| } |
| |
| return linearColor; |
| } |