DetectPlates.cpp

// DetectPlates.cpp

#include "DetectPlates.h"

///////////////////////////////////////////////////////////////////////////////////////////////////
std::vector<PossiblePlate> detectPlatesInScene(cv::Mat &imgOriginalScene) {
    std::vector<PossiblePlate> vectorOfPossiblePlates;			// this will be the return value

    cv::Mat imgGrayscaleScene;
    cv::Mat imgThreshScene;
    cv::Mat imgContours(imgOriginalScene.size(), CV_8UC3, SCALAR_BLACK);

    cv::RNG rng;

    cv::destroyAllWindows();

#ifdef SHOW_STEPS
    cv::imshow("0", imgOriginalScene);
#endif	// SHOW_STEPS

    preprocess(imgOriginalScene, imgGrayscaleScene, imgThreshScene);        // preprocess to get grayscale and threshold images

#ifdef SHOW_STEPS
    cv::imshow("1a", imgGrayscaleScene);
    cv::imshow("1b", imgThreshScene);
#endif	// SHOW_STEPS

    // find all possible chars in the scene,
    // this function first finds all contours, then only includes contours that could be chars (without comparison to other chars yet)
    std::vector<PossibleChar> vectorOfPossibleCharsInScene = findPossibleCharsInScene(imgThreshScene);

#ifdef SHOW_STEPS
    std::cout << "step 2 - vectorOfPossibleCharsInScene.Count = " << vectorOfPossibleCharsInScene.size() << std::endl;        // 131 with MCLRNF1 image

    imgContours = cv::Mat(imgOriginalScene.size(), CV_8UC3, SCALAR_BLACK);
    std::vector<std::vector<cv::Point> > contours;

    for (auto &possibleChar : vectorOfPossibleCharsInScene) {
        contours.push_back(possibleChar.contour);
    }
    cv::drawContours(imgContours, contours, -1, SCALAR_WHITE);
    cv::imshow("2b", imgContours);
#endif	// SHOW_STEPS

    // given a vector of all possible chars, find groups of matching chars
    // in the next steps each group of matching chars will attempt to be recognized as a plate
    std::vector<std::vector<PossibleChar> > vectorOfVectorsOfMatchingCharsInScene = findVectorOfVectorsOfMatchingChars(vectorOfPossibleCharsInScene);

#ifdef SHOW_STEPS
    std::cout << "step 3 - vectorOfVectorsOfMatchingCharsInScene.size() = " << vectorOfVectorsOfMatchingCharsInScene.size() << std::endl;        // 13 with MCLRNF1 image

    imgContours = cv::Mat(imgOriginalScene.size(), CV_8UC3, SCALAR_BLACK);

    for (auto &vectorOfMatchingChars : vectorOfVectorsOfMatchingCharsInScene) {
        int intRandomBlue = rng.uniform(0, 256);
        int intRandomGreen = rng.uniform(0, 256);
        int intRandomRed = rng.uniform(0, 256);

        std::vector<std::vector<cv::Point> > contours;

        for (auto &matchingChar : vectorOfMatchingChars) {
            contours.push_back(matchingChar.contour);
        }
        cv::drawContours(imgContours, contours, -1, cv::Scalar((double)intRandomBlue, (double)intRandomGreen, (double)intRandomRed));
    }
    cv::imshow("3", imgContours);
#endif	// SHOW_STEPS

    for (auto &vectorOfMatchingChars : vectorOfVectorsOfMatchingCharsInScene) {                     // for each group of matching chars
        PossiblePlate possiblePlate = extractPlate(imgOriginalScene, vectorOfMatchingChars);        // attempt to extract plate

        if (possiblePlate.imgPlate.empty() == false) {                                              // if plate was found
            vectorOfPossiblePlates.push_back(possiblePlate);                                        // add to vector of possible plates
        }
    }

    std::cout << std::endl << vectorOfPossiblePlates.size() << " possible plates found" << std::endl;       // 13 with MCLRNF1 image

#ifdef SHOW_STEPS
    std::cout << std::endl;
    cv::imshow("4a", imgContours);

    for (unsigned int i = 0; i < vectorOfPossiblePlates.size(); i++) {
        cv::Point2f p2fRectPoints[4];

        vectorOfPossiblePlates[i].rrLocationOfPlateInScene.points(p2fRectPoints);

        for (int j = 0; j < 4; j++) {
            cv::line(imgContours, p2fRectPoints[j], p2fRectPoints[(j + 1) % 4], SCALAR_RED, 2);
        }
        cv::imshow("4a", imgContours);

        std::cout << "possible plate " << i << ", click on any image and press a key to continue . . ." << std::endl;

        cv::imshow("4b", vectorOfPossiblePlates[i].imgPlate);
        cv::waitKey(0);
    }
    std::cout << std::endl << "plate detection complete, click on any image and press a key to begin char recognition . . ." << std::endl << std::endl;
    cv::waitKey(0);
#endif	// SHOW_STEPS

    return vectorOfPossiblePlates;
}

///////////////////////////////////////////////////////////////////////////////////////////////////
std::vector<PossibleChar> findPossibleCharsInScene(cv::Mat &imgThresh) {
    std::vector<PossibleChar> vectorOfPossibleChars;            // this will be the return value

    cv::Mat imgContours(imgThresh.size(), CV_8UC3, SCALAR_BLACK);
    int intCountOfPossibleChars = 0;

    cv::Mat imgThreshCopy = imgThresh.clone();

    std::vector<std::vector<cv::Point> > contours;

    cv::findContours(imgThreshCopy, contours, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);        // find all contours

    for (unsigned int i = 0; i < contours.size(); i++) {                // for each contour
#ifdef SHOW_STEPS
        cv::drawContours(imgContours, contours, i, SCALAR_WHITE);
#endif	// SHOW_STEPS
        PossibleChar possibleChar(contours[i]);

        if (checkIfPossibleChar(possibleChar)) {                // if contour is a possible char, note this does not compare to other chars (yet) . . .
            intCountOfPossibleChars++;                          // increment count of possible chars
            vectorOfPossibleChars.push_back(possibleChar);      // and add to vector of possible chars
        }
    }

#ifdef SHOW_STEPS
    std::cout << std::endl << "contours.size() = " << contours.size() << std::endl;                         // 2362 with MCLRNF1 image
    std::cout << "step 2 - intCountOfValidPossibleChars = " << intCountOfPossibleChars << std::endl;        // 131 with MCLRNF1 image
    cv::imshow("2a", imgContours);
#endif	// SHOW_STEPS

    return(vectorOfPossibleChars);
}

///////////////////////////////////////////////////////////////////////////////////////////////////
PossiblePlate extractPlate(cv::Mat &imgOriginal, std::vector<PossibleChar> &vectorOfMatchingChars) {
    PossiblePlate possiblePlate;            // this will be the return value

                                            // sort chars from left to right based on x position
    std::sort(vectorOfMatchingChars.begin(), vectorOfMatchingChars.end(), PossibleChar::sortCharsLeftToRight);

    // calculate the center point of the plate
    double dblPlateCenterX = (double)(vectorOfMatchingChars[0].intCenterX + vectorOfMatchingChars[vectorOfMatchingChars.size() - 1].intCenterX) / 2.0;
    double dblPlateCenterY = (double)(vectorOfMatchingChars[0].intCenterY + vectorOfMatchingChars[vectorOfMatchingChars.size() - 1].intCenterY) / 2.0;
    cv::Point2d p2dPlateCenter(dblPlateCenterX, dblPlateCenterY);

    // calculate plate width and height
    int intPlateWidth = (int)((vectorOfMatchingChars[vectorOfMatchingChars.size() - 1].boundingRect.x + vectorOfMatchingChars[vectorOfMatchingChars.size() - 1].boundingRect.width - vectorOfMatchingChars[0].boundingRect.x) * PLATE_WIDTH_PADDING_FACTOR);

    double intTotalOfCharHeights = 0;

    for (auto &matchingChar : vectorOfMatchingChars) {
        intTotalOfCharHeights = intTotalOfCharHeights + matchingChar.boundingRect.height;
    }

    double dblAverageCharHeight = (double)intTotalOfCharHeights / vectorOfMatchingChars.size();

    int intPlateHeight = (int)(dblAverageCharHeight * PLATE_HEIGHT_PADDING_FACTOR);

    // calculate correction angle of plate region
    double dblOpposite = vectorOfMatchingChars[vectorOfMatchingChars.size() - 1].intCenterY - vectorOfMatchingChars[0].intCenterY;
    double dblHypotenuse = distanceBetweenChars(vectorOfMatchingChars[0], vectorOfMatchingChars[vectorOfMatchingChars.size() - 1]);
    double dblCorrectionAngleInRad = asin(dblOpposite / dblHypotenuse);
    double dblCorrectionAngleInDeg = dblCorrectionAngleInRad * (180.0 / CV_PI);

    // assign rotated rect member variable of possible plate
    possiblePlate.rrLocationOfPlateInScene = cv::RotatedRect(p2dPlateCenter, cv::Size2f((float)intPlateWidth, (float)intPlateHeight), (float)dblCorrectionAngleInDeg);

    cv::Mat rotationMatrix;             // final steps are to perform the actual rotation
    cv::Mat imgRotated;
    cv::Mat imgCropped;

    rotationMatrix = cv::getRotationMatrix2D(p2dPlateCenter, dblCorrectionAngleInDeg, 1.0);         // get the rotation matrix for our calculated correction angle

    cv::warpAffine(imgOriginal, imgRotated, rotationMatrix, imgOriginal.size());            // rotate the entire image

                                                                                            // crop out the actual plate portion of the rotated image
    cv::getRectSubPix(imgRotated, possiblePlate.rrLocationOfPlateInScene.size, possiblePlate.rrLocationOfPlateInScene.center, imgCropped);

    possiblePlate.imgPlate = imgCropped;            // copy the cropped plate image into the applicable member variable of the possible plate

    return(possiblePlate);
}