如何用OpenCV实现的文档矫正？
摘要：使用 OpenCV 进行文档矫正 本文只发布于博客园与pchar博客 std::vector<std::vector<cv::Point>> cvhel
使用 OpenCV 进行文档矫正
本文只发布于博客园与pchar博客
std::vector<std::vector<cv::Point>> cvhelper::findCorners(const cv::Mat &image) {
cv::Mat gaussImage;
cv::GaussianBlur(image, gaussImage, cv::Size(5, 5), 0);
cv::threshold(gaussImage, gaussImage, 0, 255, cv::THRESH_BINARY | cv::THRESH_OTSU);
cv::Canny(gaussImage, gaussImage, 50, 200);
cv::morphologyEx(gaussImage, gaussImage, cv::MORPH_CLOSE,
cv::Mat::ones(5, 5, CV_32F));
std::vector<std::vector<cv::Point>> contours;
std::vector<cv::Vec4i> hierarchy;
cv::findContours(gaussImage, contours, hierarchy, cv::RETR_LIST, cv::CHAIN_APPROX_SIMPLE);
std::vector<std::vector<cv::Point>> ret;
for (auto &contour: contours) {
double peri = cv::arcLength(contour, true);
std::vector<cv::Point> approx;
cv::approxPolyDP(contour, approx, 0.05 * peri, true);
if (approx.size() == 4 && cv::isContourConvex(approx) && cv::contourArea(approx) > 1000) {
ret.push_back(approx);
}
}
return ret;
}
void cvhelper::GetDocumentRect(cv::Mat &src, std::vector<cv::Point> &ret_points) {
int shrunkImageHeight = 500;
cv::Mat shrunkImage;
cv::resize(src, shrunkImage, cv::Size(shrunkImageHeight * src.cols / src.rows, shrunkImageHeight));
cv::cvtColor(shrunkImage, shrunkImage, cv::COLOR_BGR2Luv);
std::vector<cv::Mat> channels;
cv::split(shrunkImage, channels);
std::vector<std::vector<cv::Point>> documentCorners;
for (const auto &channel: channels) {
std::vector<std::vector<cv::Point>> corners = findCorners(channel);
if (!corners.empty()) {
double maxArea = 0.0;
std::vector<cv::Point> maxAreaContourIt;
for (const auto &contour: corners) {
double area = cv::contourArea(contour);
if (area > maxArea) {
maxArea = area;
maxAreaContourIt = contour;
}
}
if (maxArea > 0) {
std::vector<cv::Point> scaledContour;
for (const auto &point: maxAreaContourIt) {
cv::Point scaledPoint;
scaledPoint.x = static_cast<int>(point.x * static_cast<double>(src.rows) /
shrunkImageHeight);
scaledPoint.y = static_cast<int>(point.y * static_cast<double>(src.rows) /
shrunkImageHeight);
scaledContour.push_back(scaledPoint);
}
documentCorners.push_back(scaledContour);
}
}
}
if (documentCorners.size() == 0) {
return;
}
std::vector<cv::Point> maxDocumentCorners;
double maxDocumentArea = 0.0;
for (const auto &documentCorner: documentCorners) {
double area = cv::contourArea(documentCorner);
if (area > maxDocumentArea) {
maxDocumentArea = area;
maxDocumentCorners = documentCorner;
}
}
ret_points = maxDocumentCorners;
}
cv::Mat cvhelper::CutKeyPosition(cv::Mat &src, std::vector<cv::Point2f> &src_points) {
// 透视变换
cv::Point2f dst_points[4];
dst_points[0] = cv::Point2f(src.cols, 0);
dst_points[1] = cv::Point2f(0, 0);
dst_points[2] = cv::Point2f(0, src.rows);
dst_points[3] = cv::Point2f(src.cols, src.rows);
cv::Point2f tL = src_points[1];
cv::Point2f tR = src_points[0];
cv::Point2f bR = src_points[3];
cv::Point2f bL = src_points[2];
int width = (std::min)(cv::norm(tR - tL), cv::norm(bR - bL));
int height = (std::min)(cv::norm(tR - bR), cv::norm(tL - bL));
cv::Mat M = cv::getPerspectiveTransform(src_points.data(), dst_points);
cv::Mat dst;
cv::warpPerspective(src, dst, M, src.size());
// 缩放图像
cv::resize(dst, dst, cv::Size(width, height));
return dst;
}
效果展示