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//
// Three Frequency Phase Shifting using the Heterodyne Principle
//
// This implementation follows "Reich, Ritter, Thesing, White light heterodyne principle for 3D-measurement", SPIE (1997)
//
// The number of periods in the primary and secondary frequencies can be chosen freely, but small changes can have a considerable impact on quality.
// The number of phase shifts can be chosen freely (min. 3), and higher values reduce the effects of image noise. They also allow us to filter bad points based on energy at non-primary frequencies.
//
#include "AlgorithmPhaseShiftThreeFreq.h"
#include <math.h>
#include "cvtools.h"
#include "algorithmtools.h"
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
static unsigned int nStepsPrimary = 8; // number of shifts/steps in primary
static unsigned int nStepsSecondary = 8; // number of shifts/steps in secondary
static unsigned int nStepsTertiary = 8; // number of shifts/steps in tertiary
static float nPeriodsPrimary = 24; // primary period
static float nPeriodsSecondary = 30; // primary period
AlgorithmPhaseShiftThreeFreq::AlgorithmPhaseShiftThreeFreq(unsigned int _screenCols, unsigned int _screenRows) : Algorithm(_screenCols, _screenRows){
// Set N
N = 2+nStepsPrimary+nStepsSecondary+nStepsTertiary;
// Determine the tertiary period to fulfill the heterodyne condition
float nPeriodsTertiary = (screenCols*nPeriodsPrimary*nPeriodsSecondary)/(nPeriodsPrimary*nPeriodsSecondary+2*screenCols*nPeriodsPrimary-screenCols*nPeriodsSecondary);
// all on pattern
cv::Mat allOn(1, screenCols, CV_8UC3, cv::Scalar::all(255));
patterns.push_back(allOn);
// all off pattern
cv::Mat allOff(1, screenCols, CV_8UC3, cv::Scalar::all(0));
patterns.push_back(allOff);
// Precompute encoded patterns
const float pi = M_PI;
// Primary encoding patterns
for(unsigned int i=0; i<nStepsPrimary; i++){
float phase = 2.0*pi/nStepsPrimary * i;
float pitch = screenCols/nPeriodsPrimary;
cv::Mat patternI(1,1,CV_8U);
patternI = computePhaseVector(screenCols, phase, pitch);
patterns.push_back(patternI.t());
}
// Secondary encoding patterns
for(unsigned int i=0; i<nStepsSecondary; i++){
float phase = 2.0*pi/nStepsSecondary * i;
float pitch = screenCols/nPeriodsSecondary;
cv::Mat patternI(1,1,CV_8U);
patternI = computePhaseVector(screenCols, phase, pitch);
patterns.push_back(patternI.t());
}
// Tertiary encoding patterns
for(unsigned int i=0; i<nStepsTertiary; i++){
float phase = 2.0*pi/nStepsTertiary * i;
float pitch = screenCols/nPeriodsTertiary;
cv::Mat patternI(1,1,CV_8U);
patternI = computePhaseVector(screenCols, phase, pitch);
patterns.push_back(patternI.t());
}
}
cv::Mat AlgorithmPhaseShiftThreeFreq::getEncodingPattern(unsigned int depth){
return patterns[depth];
}
void AlgorithmPhaseShiftThreeFreq::get3DPoints(SMCalibrationParameters calibration, const std::vector<cv::Mat>& frames0, const std::vector<cv::Mat>& frames1, std::vector<cv::Point3f>& Q, std::vector<cv::Vec3b>& color){
const float pi = M_PI;
assert(frames0.size() == N);
assert(frames1.size() == N);
int frameRows = frames0[0].rows;
int frameCols = frames0[0].cols;
// Rectifying homographies (rotation+projections)
cv::Size frameSize(frameCols, frameRows);
cv::Mat R, T;
// stereoRectify segfaults unless R is double precision
cv::Mat(calibration.R1).convertTo(R, CV_64F);
cv::Mat(calibration.T1).convertTo(T, CV_64F);
cv::Mat R0, R1, P0, P1, QRect;
cv::stereoRectify(calibration.K0, calibration.k0, calibration.K1, calibration.k1, frameSize, R, T, R0, R1, P0, P1, QRect, 0);
// Interpolation maps (lens distortion and rectification)
cv::Mat map0X, map0Y, map1X, map1Y;
cv::initUndistortRectifyMap(calibration.K0, calibration.k0, R0, P0, frameSize, CV_32F, map0X, map0Y);
cv::initUndistortRectifyMap(calibration.K1, calibration.k1, R1, P1, frameSize, CV_32F, map1X, map1Y);
// Gray-scale and remap
std::vector<cv::Mat> frames0Rect(N);
std::vector<cv::Mat> frames1Rect(N);
for(unsigned int i=0; i<N; i++){
cv::Mat temp;
cv::cvtColor(frames0[i], temp, CV_BayerBG2GRAY);
cv::remap(temp, frames0Rect[i], map0X, map0Y, CV_INTER_LINEAR);
cv::cvtColor(frames1[i], temp, CV_BayerBG2GRAY);
cv::remap(temp, frames1Rect[i], map1X, map1Y, CV_INTER_LINEAR);
}
// Decode camera0
std::vector<cv::Mat> frames0Primary(frames0Rect.begin()+2, frames0Rect.begin()+2+nStepsPrimary);
std::vector<cv::Mat> frames0Secondary(frames0Rect.begin()+2+nStepsPrimary, frames0Rect.end()-nStepsTertiary);
std::vector<cv::Mat> frames0Tertiary(frames0Rect.end()-nStepsTertiary, frames0Rect.end());
std::vector<cv::Mat> F0Primary = getDFTComponents(frames0Primary);
cv::Mat up0Primary;
cv::phase(F0Primary[2], -F0Primary[3], up0Primary);
std::vector<cv::Mat> F0Secondary = getDFTComponents(frames0Secondary);
cv::Mat up0Secondary;
cv::phase(F0Secondary[2], -F0Secondary[3], up0Secondary);
std::vector<cv::Mat> F0Tertiary = getDFTComponents(frames0Tertiary);
cv::Mat up0Tertiary;
cv::phase(F0Tertiary[2], -F0Tertiary[3], up0Tertiary);
cv::Mat up0EquivalentPS = up0Primary - up0Secondary;
up0EquivalentPS = cvtools::modulo(up0EquivalentPS, 2.0*pi);
cv::Mat up0EquivalentST = up0Secondary - up0Tertiary;
up0EquivalentST = cvtools::modulo(up0EquivalentST, 2.0*pi);
cv::Mat up0Equivalent = up0EquivalentPS - up0EquivalentST;
up0Equivalent = cvtools::modulo(up0Equivalent, 2.0*pi);
cv::Mat up0 = unwrapWithCue(up0Primary, up0Equivalent, (float)screenCols/nPeriodsPrimary);
up0 *= screenCols/(2.0*pi);
cv::Mat amplitude0;
cv::magnitude(F0Primary[2], -F0Primary[3], amplitude0);
// Decode camera1
std::vector<cv::Mat> frames1Primary(frames1Rect.begin()+2, frames1Rect.begin()+2+nStepsPrimary);
std::vector<cv::Mat> frames1Secondary(frames1Rect.begin()+2+nStepsPrimary, frames1Rect.end()-nStepsTertiary);
std::vector<cv::Mat> frames1Tertiary(frames1Rect.end()-nStepsTertiary, frames1Rect.end());
std::vector<cv::Mat> F1Primary = getDFTComponents(frames1Primary);
cv::Mat up1Primary;
cv::phase(F1Primary[2], -F1Primary[3], up1Primary);
std::vector<cv::Mat> F1Secondary = getDFTComponents(frames1Secondary);
cv::Mat up1Secondary;
cv::phase(F1Secondary[2], -F1Secondary[3], up1Secondary);
std::vector<cv::Mat> F1Tertiary = getDFTComponents(frames1Tertiary);
cv::Mat up1Tertiary;
cv::phase(F1Tertiary[2], -F1Tertiary[3], up1Tertiary);
cv::Mat up1EquivalentPS = up1Primary - up1Secondary;
up1EquivalentPS = cvtools::modulo(up1EquivalentPS, 2.0*pi);
cv::Mat up1EquivalentST = up1Secondary - up1Tertiary;
up1EquivalentST = cvtools::modulo(up1EquivalentST, 2.0*pi);
cv::Mat up1Equivalent = up1EquivalentPS - up1EquivalentST;
up1Equivalent = cvtools::modulo(up1Equivalent, 2.0*pi);
cv::Mat up1 = unwrapWithCue(up1Primary, up1Equivalent, (float)screenCols/nPeriodsPrimary);
up1 *= screenCols/(2.0*pi);
cv::Mat amplitude1;
cv::magnitude(F1Primary[2], -F1Primary[3], amplitude1);
#ifdef Q_DEBUG
cvtools::writeMat(up0Primary, "up0Primary.mat", "up0Primary");
cvtools::writeMat(up0Secondary, "up0Secondary.mat", "up0Secondary");
cvtools::writeMat(up0Tertiary, "up0Tertiary.mat", "up0Tertiary");
cvtools::writeMat(up0EquivalentPS, "up0EquivalentPS.mat", "up0EquivalentPS");
cvtools::writeMat(up0EquivalentST, "up0EquivalentST.mat", "up0EquivalentST");
cvtools::writeMat(up0, "up0.mat", "up0");
cvtools::writeMat(up1, "up1.mat", "up1");
cvtools::writeMat(amplitude0, "amplitude0.mat", "amplitude0");
cvtools::writeMat(amplitude0, "amplitude0.mat", "amplitude0");
cvtools::writeMat(amplitude1, "amplitude1.mat", "amplitude1");
#endif
// Color debayer and remap
cv::Mat color0, color1;
cv::cvtColor(frames0[0], color0, CV_BayerBG2RGB);
cv::cvtColor(frames1[0], color1, CV_BayerBG2RGB);
#ifdef Q_DEBUG
cvtools::writeMat(color0, "color0.mat", "color0");
cvtools::writeMat(color1, "color1.mat", "color1");
#endif
// Occlusion masks
cv::Mat occlusion0, occlusion1;
cv::subtract(frames0Rect[0], frames0Rect[1], occlusion0);
occlusion0 = (occlusion0 > 5) & (occlusion0 < 250);
cv::subtract(frames1Rect[0], frames1Rect[1], occlusion1);
occlusion1 = (occlusion1 > 5) & (occlusion1 < 250);
#ifdef Q_DEBUG
// Erode occlusion masks
cv::Mat strel = cv::getStructuringElement(cv::MORPH_ELLIPSE, cv::Size(5,5));
cv::erode(occlusion0, occlusion0, strel);
cv::erode(occlusion1, occlusion1, strel);
#endif
// Threshold on gradient of phase
cv::Mat edges0;
cv::Sobel(up0, edges0, -1, 1, 1, 5);
occlusion0 = occlusion0 & (abs(edges0) < 150);
cv::Mat edges1;
cv::Sobel(up1, edges1, -1, 1, 1, 5);
occlusion1 = occlusion1 & (abs(edges1) < 150);
#ifdef Q_DEBUG
cvtools::writeMat(edges0, "edges0.mat", "edges0");
cvtools::writeMat(edges1, "edges1.mat", "edges1");
#endif
// Match phase maps
int frameRectRows = map0X.rows;
int frameRectCols = map0X.cols;
// camera0 against camera1
std::vector<cv::Vec2f> q0, q1;
for(int row=0; row<frameRectRows; row++){
for(int col=0; col<frameRectCols; col++){
if(!occlusion0.at<char>(row,col))
continue;
float up0i = up0.at<float>(row,col);
for(int col1=0; col1<up1.cols-1; col1++){
if(!occlusion1.at<char>(row,col1) || !occlusion1.at<char>(row,col1+1))
continue;
float up1Left = up1.at<float>(row,col1);
float up1Right = up1.at<float>(row,col1+1);
if((up1Left <= up0i) && (up0i <= up1Right) && (up0i-up1Left < 1.0) && (up1Right-up0i < 1.0)){
float col1i = col1 + (up0i-up1Left)/(up1Right-up1Left);
q0.push_back(cv::Point2f(col, row));
q1.push_back(cv::Point2f(col1i, row));
break;
}
}
}
}
int nMatches = q0.size();
if(nMatches < 1){
Q.resize(0);
color.resize(0);
return;
}
// Retrieve color information
color.resize(nMatches);
for(int i=0; i<nMatches; i++){
cv::Vec3b c0 = color0.at<cv::Vec3b>(q0[i][1], q0[i][0]);
cv::Vec3b c1 = color1.at<cv::Vec3b>(q1[i][1], q1[i][0]);
color[i] = 0.5*c0 + 0.5*c1;
}
// Triangulate points
cv::Mat QMatHomogenous, QMat;
cv::triangulatePoints(P0, P1, q0, q1, QMatHomogenous);
cvtools::convertMatFromHomogeneous(QMatHomogenous, QMat);
// Undo rectification
cv::Mat R0Inv;
cv::Mat(R0.t()).convertTo(R0Inv, CV_32F);
QMat = R0Inv*QMat;
cvtools::matToPoints3f(QMat, Q);
}