官網教程
文章目錄
- 一、翻轉(鏡像)
- 二、仿射扭曲
- 擷取變換矩陣
- 仿射扭曲函數 warpAffine
- 旋轉
- 平移
- 三、仿射變換
- 四、透視變換
- 綜合示例
一、翻轉(鏡像)
頭檔案
quick_opencv.h
:聲明類與公共函數
#pragma once
#include <opencv2\opencv.hpp>
using namespace cv;
class QuickDemo {
public:
...
void flip_Demo(Mat& image);
void rotate_Demo(Mat& image);
void move_Demo(Mat& image);
void Affine_Demo(Mat& image);
void toushi_Demo(Mat& image);
void perspective_detect(Mat& image);
};
主函數調用該類的公共成員函數
#include <opencv2\opencv.hpp>
#include <quick_opencv.h>
#include <iostream>
using namespace cv;
int main(int argc, char** argv) {
Mat src = imread("D:\\Desktop\\pandas.jpg");
if (src.empty()) {
printf("Could not load images...\n");
return -1;
}
namedWindow("input", WINDOW_NORMAL);
imshow("input", src);
QuickDemo qk;
...
qk.Affine_Demo(src);
qk.move_Demo(src);
qk.flip_Demo(src);
qk.toushi_Demo(src);
qk.perspective_detect(src);
waitKey(0);
destroyAllWindows();
return 0;
}
源檔案
quick_demo.cpp
:實作類與公共函數
void QuickDemo::flip_Demo(Mat& image) {
Mat dst0, dst1, dst2;
flip(image, dst0, 0);
flip(image, dst1, 1);
flip(image, dst2, -1);
imshow("dst0_上下翻轉", dst0);
imshow("dst1_左右翻轉", dst1);
imshow("dst2_對角線翻轉", dst2); //旋轉180度
}
![](https://img.laitimes.com/img/_0nNw4CM6IyYiwiM6ICdiwiI0gTMx81dsQWZ4lmZf1GLlpXazVmcvwFciV2dsQXYtJ3bm9CX9s2RkBnVHFmb1clWvB3MaVnRtp1XlBXe0xCMy81dvRWYoNHLwEzX5xCMx8FesU2cfdGLwMzX0xiRGZkRGZ0Xy9GbvNGLpZTY1EmMZVDUSFTU4VFRR9Fd4VGdsYTMfVmepNHLrJXYtJXZ0F2dvwVZnFWbp1zczV2YvJHctM3cv1Ce-cmbw5CMzATNzcTY3IWZ4ADNzEDZyYzXyUTMzcTM1EzLcdDMyIDMy8CXn9Gbi9CXzV2Zh1WavwVbvNmLvR3YxUjLyM3Lc9CX6MHc0RHaiojIsJye.png)
二、仿射扭曲
二維圖像一般情況下的變換矩陣(旋轉+平移),當我們隻需要平移的時候,取 的值為0,a和b的值就代表了圖像沿x軸和y軸移動的距離;其中原圖 Scalar=1(原圖大小,不執行縮放)
擷取變換矩陣
變換矩陣計算:
其中:
Point2f center, 源圖像中旋轉的中心
double angle, 角度以度為機關的旋轉角度。正值表示逆時針旋轉(坐标原點假定為左上角)。
double scale 各向同性比例因子。
)
仿射扭曲函數 warpAffine
函數簽名
InputArray
src, 輸入矩陣
OutputArray
dst, 輸出矩陣
InputArray
M, 2×3 變換矩陣
Size
dsize, 輸出圖像大小
int
flags = INTER_LINEAR, 插值方式:預設線性插值
int
borderMode = BORDER_CONSTANT, 邊緣處理方式
const Scalar&
borderValue = Scalar() 邊緣填充值,預設=0
);
保留所有原圖像素的旋轉,原理:
new_h =
旋轉
void QuickDemo::rotate_Demo(Mat& image) {
Mat dst_0, dst_1, M;
int h = image.rows;
int w = image.cols;
M = getRotationMatrix2D(Point(w / 2, h / 2), 45, 1.0);
warpAffine(image, dst_0, M, image.size());
double cos = abs(M.at<double>(0, 0));
double sin = abs(M.at<double>(0, 1));
int new_w = cos * w + sin * h;
int new_h = cos * h + sin * w;
M.at<double>(0, 2) += (new_w / 2.0 - w / 2);
M.at<double>(1, 2) += (new_h / 2.0 - h / 2);
warpAffine(image, dst_1, M, Size(new_w, new_h), INTER_LINEAR, 0, Scalar(255, 255, 0));
imshow("旋轉示範0", dst_0);
imshow("旋轉示範1", dst_1);
}
依次為:原圖,旋轉45度,保留所有原圖像素的旋轉45度
平移
void QuickDemo::move_Demo(Mat& image) {
Mat dst_move;
Mat move_mat = (Mat_<double>(2, 3) << 1, 0, 10, 0, 1, 30);//沿x軸移動10沿y軸移動30
warpAffine(image, dst_move, move_mat, image.size());
imshow("dst_move", dst_move);
double angle_ = 3.14159265354 / 16.0;
cout << "pi=" << cos(angle_) << endl;
Mat rota_mat = (Mat_<double>(2, 3) << cos(angle_), -sin(angle_), 1, sin(angle_), cos(angle_), 1);
warpAffine(image, rotate_dst, rota_mat, image.size());
imshow("rotate_dst", rotate_dst);
}
三、仿射變換
Mat getAffineTransform( 傳回變換矩陣
const Point2f src[], 變換前三個點的數組
const Point2f dst[] 變換後三個點的數組
);
void QuickDemo::Affine_Demo(Mat& image) {
Mat warp_dst;
Mat warp_mat(2, 3, CV_32FC1);
Point2f srcTri[3];
Point2f dstTri[3];
/// 設定源圖像和目标圖像上的三組點以計算仿射變換
srcTri[0] = Point2f(0, 0);
srcTri[1] = Point2f(image.cols - 1, 0);
srcTri[2] = Point2f(0, image.rows - 1);
for (size_t i = 0; i < 3; i++){
circle(image, srcTri[i], 2, Scalar(0, 0, 255), 5, 8);
}
dstTri[0] = Point2f(image.cols * 0.0, image.rows * 0.13);
dstTri[1] = Point2f(image.cols * 0.95, image.rows * 0.15);
dstTri[2] = Point2f(image.cols * 0.15, image.rows * 0.9);
warp_mat = getAffineTransform(srcTri, dstTri);
warpAffine(image, warp_dst, warp_mat, warp_dst.size());
imshow("warp_dst", warp_dst);
}
四、透視變換
擷取透射變換的矩陣:
Mat getPerspectiveTransform( 傳回變換矩陣
const Point2f src[], 透視變換前四個點的
數組
const Point2f dst[], 透視變換後四個點的
數組
int solveMethod = DECOMP_LU
)
透射變換
InputArray src, 原圖像
OutputArray dst, 傳回圖像
InputArray M, 透視變換矩陣
Size dsize, 傳回圖像的大小(寬,高)
int flags = INTER_LINEAR, 插值方法
int borderMode = BORDER_CONSTANT, 邊界處理
const Scalar& borderValue = Scalar() 縮放處理
)
void QuickDemo::toushi_Demo(Mat& image) {
Mat toushi_dst, toushi_mat;
Point2f toushi_before[4];
toushi_before[0] = Point2f(122, 220);
toushi_before[1] = Point2f(397, 121);
toushi_before[2] = Point2f(133, 339);
toushi_before[3] = Point2f(397, 218);
int width_0 = toushi_before[1].x - toushi_before[0].x;
int height_0 = toushi_before[1].y - toushi_before[0].y;
int width_1 = toushi_before[2].x - toushi_before[0].x;
int height_1 = toushi_before[2].y - toushi_before[0].y;
int width = (int)sqrt(width_0 * width_0 + height_0 * height_0);
int height = (int)sqrt(width_1 * width_1 + height_1 * height_1);
Point2f toushi_after[4];
toushi_after[0] = Point2f(2, 2); // x0, y0
toushi_after[1] = Point2f(width+2, 2); // x1, y0
toushi_after[2] = Point2f(2, height+2); // x0, y1
toushi_after[3] = Point2f(width + 2, height + 2); // x1, y1
for (size_t i = 0; i < 4; i++){
cout << toushi_after[i] << endl;
}
toushi_mat = getPerspectiveTransform(toushi_before, toushi_after);
warpPerspective(image, toushi_dst, toushi_mat, Size(width, height));
imshow("toushi_dst", toushi_dst);
}
綜合示例
自動化透視矯正圖像:
流程:
- 灰階化二值化
- 形态學去除噪點
- 擷取輪廓
- 檢測直線
- 計算直線交點
- 擷取四個透視頂點
- 透視變換
inline void Intersection(Point2i& interPoint, Vec4i& line1, Vec4i& line2) {
// x1, y1, x2, y2 = line1[0], line1[1], line1[2], line1[3]
int A1 = line1[3] - line1[1];
int B1 = line1[0] - line1[2];
int C1 = line1[1] * line1[2] - line1[0] * line1[3];
int A2 = line2[3] - line2[1];
int B2 = line2[0] - line2[2];
int C2 = line2[1] * line2[2] - line2[0] * line2[3];
interPoint.x = static_cast<int>((B1 * C2 - B2 * C1) / (A1 * B2 - A2 * B1));
interPoint.y = static_cast<int>((C1 * A2 - A1 * C2) / (A1 * B2 - A2 * B1));
}
void QuickDemo::perspective_detect(Mat& image) {
Mat gray_dst, binary_dst, morph_dst;
// 二值化
cvtColor(image, gray_dst, COLOR_BGR2GRAY);
threshold(gray_dst, binary_dst, 0, 255, THRESH_BINARY_INV | THRESH_OTSU);
//形态學操作
Mat kernel = getStructuringElement(MORPH_RECT, Size(5, 5));
morphologyEx(binary_dst, morph_dst, MORPH_CLOSE, kernel, Point(-1, -1), 3);
bitwise_not(morph_dst, morph_dst);
imshow("morph_dst2", morph_dst);
//輪廓查找與可視化
vector<vector<Point>> contours;
vector<Vec4i> hierarches;
int height = image.rows;
int width = image.cols;
Mat contours_Img = Mat::zeros(image.size(), CV_8UC3);
findContours(morph_dst, contours, hierarches, RETR_TREE, CHAIN_APPROX_SIMPLE);
for (size_t i = 0; i < contours.size(); i++){
Rect rect = boundingRect(contours[i]);
if (rect.width > width / 2 && rect.width < width - 5) {
drawContours(contours_Img, contours, i, Scalar(0, 0, 255), 2, 8, hierarches, 0, Point());
}
}
imshow("contours_Img", contours_Img);
vector<Vec4i> lines;
Mat houghImg;
int accu = min(width * 0.5, height * 0.5);
cvtColor(contours_Img, houghImg, COLOR_BGR2GRAY);
HoughLinesP(houghImg, lines, 1, CV_PI / 180, accu, accu*0.6, 0);
Mat lineImg = Mat::zeros(image.size(), CV_8UC3);
for (size_t i = 0; i < lines.size(); i++){
Vec4i ln = lines[i];
line(lineImg, Point(ln[0], ln[1]), Point(ln[2], ln[3]), Scalar(0, 0, 255), 2, 8, 0);
}
// 尋找與定位上下左右四條直線
int delta = 0;
Vec4i topline = { 0, 0, 0, 0 };
Vec4i bottomline;
Vec4i leftline, rightline;
for (size_t i = 0; i < lines.size(); i++) {
Vec4i ln = lines[i];
delta = abs(ln[3] - ln[1]); // y2-y1
//topline
if (ln[3] < height / 2.0 && ln[1] < height / 2.0 && delta < accu - 1) {
if (topline[3] > ln[3] && topline[3] > 0) {
topline = lines[i];
}
else {
topline = lines[i];
}
}
if (ln[3] > height / 2.0 && ln[1] > height / 2.0 && delta < accu - 1) {
bottomline = lines[i];
}
if (ln[0] < width / 2.0 && ln[2] < width / 2.0) {
leftline = lines[i];
}
if (ln[0] > width / 2.0 && ln[2] > width / 2.0) {
rightline = lines[i];
}
}
cout << "topline: " << topline << endl;
cout << "bottomline: " << bottomline << endl;
cout << "leftline: " << leftline << endl;
cout << "rightline: " << rightline << endl;
// 計算上述四條直線交點(兩條線的交點:依次為左上,右上,左下,右下)
Point2i p0, p1, p2, p3;
Intersection(p0, topline, leftline);
Intersection(p1, topline, rightline);
Intersection(p2, bottomline, leftline);
Intersection(p3, bottomline, rightline);
circle(lineImg, p0, 2, Scalar(255, 0, 0), 2, 8, 0);
circle(lineImg, p1, 2, Scalar(255, 0, 0), 2, 8, 0);
circle(lineImg, p2, 2, Scalar(255, 0, 0), 2, 8, 0);
circle(lineImg, p3, 2, Scalar(255, 0, 0), 2, 8, 0);
imshow("Intersection", lineImg);
//透視變換
vector<Point2f> src_point(4);
src_point[0] = p0;
src_point[1] = p1;
src_point[2] = p2;
src_point[3] = p3;
int new_height = max(abs(p2.y - p0.y), abs(p3.y - p1.y));
int new_width = max(abs(p1.x - p0.x), abs(p3.x - p2.x));
cout << "new_height = " << new_height << endl;
cout << "new_width = " << new_width << endl;
vector<Point2f> dst_point(4);
dst_point[0] = Point(0,0);
dst_point[1] = Point(new_width, 0);
dst_point[2] = Point(0, new_height);
dst_point[3] = Point(new_width, new_height);
Mat resultImg;
Mat wrap_mat = getPerspectiveTransform(src_point, dst_point);
warpPerspective(image, resultImg, wrap_mat, Size(new_width, new_height));
imshow("resultImg", resultImg);
}
關鍵步驟可視化