Mat PreProcessingFilter::getPreprocessedFace(Mat &srcImg, int desiredFaceWidth, int desiredFaceHeight, bool doLeftAndRightSeparately)
{
Mat faceImg = srcImg;
Mat gray;
if (faceImg.channels() == 3)
{
cvtColor(faceImg, gray, CV_BGR2GRAY);
}
else if (faceImg.channels() == 4)
{
cvtColor(faceImg, gray, CV_BGRA2GRAY);
}
else
{
gray = faceImg;
}
if (!doLeftAndRightSeparately)
{
equalizeHist(gray, gray);
}
else
{
equalizeLeftAndRightHalves(gray);
}
Size s(desiredFaceWidth, desiredFaceHeight);
Mat dstImg;
resize(gray, dstImg, s);
return dstImg;
}
// Create a grayscale face image that has a standard size and contrast & brightness.
// "srcImg" should be a copy of the whole color camera frame, so that it can draw the eye positions onto.
// If 'doLeftAndRightSeparately' is true, it will process left & right sides seperately,
// so that if there is a strong light on one side but not the other, it will still look OK.
// Performs Face Preprocessing as a combination of:
// - geometrical scaling, rotation and translation using Eye Detection,
// - smoothing away image noise using a Bilateral Filter,
// - standardize the brightness on both left and right sides of the face independently using separated Histogram Equalization,
// - removal of background and hair using an Elliptical Mask.
// Returns either a preprocessed face square image or NULL (ie: couldn't detect the face and 2 eyes).
// If a face is found, it can store the rect coordinates into 'storeFaceRect' and 'storeLeftEye' & 'storeRightEye' if given,
// and eye search regions into 'searchedLeftEye' & 'searchedRightEye' if given.
cv::Mat preprocessFace::getPreprocessedFace(cv::Mat &srcImg, int desiredFaceWidth, cv::CascadeClassifier &faceCascade, cv::CascadeClassifier &eyeCascade1, cv::CascadeClassifier &eyeCascade2, bool doLeftAndRightSeparately, cv::Rect *storeFaceRect, cv::Point *storeLeftEye, cv::Point *storeRightEye, cv::Rect *searchedLeftEye, cv::Rect *searchedRightEye)
{
// Use square faces.
int desiredFaceHeight = desiredFaceWidth;
// Mark the detected face region and eye search regions as invalid, in case they aren't detected.
if (storeFaceRect)
storeFaceRect->width = -1;
if (storeLeftEye)
storeLeftEye->x = -1;
if (storeRightEye)
storeRightEye->x = -1;
if (searchedLeftEye)
searchedLeftEye->width = -1;
if (searchedRightEye)
searchedRightEye->width = -1;
// Find the largest face.
cv::Rect faceRect;
detector.detectLargestObject(srcImg, faceCascade, faceRect);
// Check if a face was detected.
if (faceRect.width > 0) {
// Give the face rect to the caller if desired.
if (storeFaceRect)
*storeFaceRect = faceRect;
cv::Mat faceImg = srcImg(faceRect); // Get the detected face image.
// If the input image is not grayscale, then convert the BGR or BGRA color image to grayscale.
cv::Mat gray;
if (faceImg.channels() == 3) {
cvtColor(faceImg, gray, CV_BGR2GRAY);
}
else if (faceImg.channels() == 4) {
cvtColor(faceImg, gray, CV_BGRA2GRAY);
}
else {
// Access the input image directly, since it is already grayscale.
gray = faceImg;
}
// Search for the 2 eyes at the full resolution, since eye detection needs max resolution possible!
cv::Point leftEye, rightEye;
detectBothEyes(gray, eyeCascade1, eyeCascade2, leftEye, rightEye, searchedLeftEye, searchedRightEye);
// Give the eye results to the caller if desired.
if (storeLeftEye)
*storeLeftEye = leftEye;
if (storeRightEye)
*storeRightEye = rightEye;
// Check if both eyes were detected.
if (leftEye.x >= 0 && rightEye.x >= 0)
{
inputFaceCount++;
// Make the face image the same size as the training images.
// Since we found both eyes, lets rotate & scale & translate the face so that the 2 eyes
// line up perfectly with ideal eye positions. This makes sure that eyes will be horizontal,
// and not too far left or right of the face, etc.
// Get the center between the 2 eyes.
cv::Point2f eyesCenter = cv::Point2f((leftEye.x + rightEye.x) * 0.5f, (leftEye.y + rightEye.y) * 0.5f);
// Get the angle between the 2 eyes.
double dy = (rightEye.y - leftEye.y);
double dx = (rightEye.x - leftEye.x);
double len = sqrt(dx*dx + dy*dy);
double angle = atan2(dy, dx) * 180.0 / CV_PI; // Convert from radians to degrees.
// Hand measurements shown that the left eye center should ideally be at roughly (0.19, 0.14) of a scaled face image.
const double DESIRED_RIGHT_EYE_X = (1.0f - DESIRED_LEFT_EYE_X);
// Get the amount we need to scale the image to be the desired fixed size we want.
double desiredLen = (DESIRED_RIGHT_EYE_X - DESIRED_LEFT_EYE_X) * desiredFaceWidth;
double scale = desiredLen / len;
// Get the transformation matrix for rotating and scaling the face to the desired angle & size.
cv::Mat rot_mat = getRotationMatrix2D(eyesCenter, angle, scale);
// Shift the center of the eyes to be the desired center between the eyes.
rot_mat.at<double>(0, 2) += desiredFaceWidth * 0.5f - eyesCenter.x;
rot_mat.at<double>(1, 2) += desiredFaceHeight * DESIRED_LEFT_EYE_Y - eyesCenter.y;
// Rotate and scale and translate the image to the desired angle & size & position!
// Note that we use 'w' for the height instead of 'h', because the input face has 1:1 aspect ratio.
cv::Mat warped = cv::Mat(desiredFaceHeight, desiredFaceWidth, CV_8U, cv::Scalar(128)); // Clear the output image to a default grey.
warpAffine(gray, warped, rot_mat, warped.size());
//imshow("warped", warped);
// Give the image a standard brightness and contrast, in case it was too dark or had low contrast.
if (!doLeftAndRightSeparately) {
// Do it on the whole face.
equalizeHist(warped, warped);
}
else {
// Do it seperately for the left and right sides of the face.
equalizeLeftAndRightHalves(warped);
}
//imshow("equalized", warped);
// Use the "Bilateral Filter" to reduce pixel noise by smoothing the image, but keeping the sharp edges in the face.
cv::Mat filtered = cv::Mat(warped.size(), CV_8U);
bilateralFilter(warped, filtered, 0, 20.0, 2.0);
//imshow("filtered", filtered);
// Filter out the corners of the face, since we mainly just care about the middle parts.
// Draw a filled ellipse in the middle of the face-sized image.
cv::Mat mask = cv::Mat(warped.size(), CV_8U, cv::Scalar(0)); // Start with an empty mask.
cv::Point faceCenter = cv::Point(desiredFaceWidth / 2, cvRound(desiredFaceHeight * FACE_ELLIPSE_CY));
cv::Size size = cv::Size(cvRound(desiredFaceWidth * FACE_ELLIPSE_W), cvRound(desiredFaceHeight * FACE_ELLIPSE_H));
ellipse(mask, faceCenter, size, 0, 0, 360, cv::Scalar(255), CV_FILLED);
//imshow("mask", mask);
// Use the mask, to remove outside pixels.
cv::Mat dstImg = cv::Mat(warped.size(), CV_8U, cv::Scalar(128)); // Clear the output image to a default gray.
/*
namedWindow("filtered");
imshow("filtered", filtered);
namedWindow("dstImg");
imshow("dstImg", dstImg);
namedWindow("mask");
imshow("mask", mask);
*/
// Apply the elliptical mask on the face.
filtered.copyTo(dstImg, mask); // Copies non-masked pixels from filtered to dstImg.
//imshow("dstImg", dstImg);
/*if (leftEye.x >= 0 && rightEye.x >= 0)
{
eyeRegion.x = 0;
eyeRegion.y = searchedLeftEye.y;
eyeRegion.width = preprocessedFace.rows;
eyeRegion.height = 30;
cv::rectangle(frame, eyeRegion, CV_RGB(255, 255, 0), 3);
}*/
if (needResults)
{
writeResults(srcImg, gray, dstImg);
}
return dstImg;
}
/*
else {
// Since no eyes were found, just do a generic image resize.
resize(gray, tmpImg, Size(w,h));
}
*/
}
return cv::Mat();
}
