java图形几何变换,OpenCV图像几何变换之透视变换

本文实例为大家分享了Android九宫格图片展示的具体代码，供大家参考，具体内容如下

1. 基本原理

透视变换(Perspective Transformation)的本质是将图像投影到一个新的视平面，其通用变换公式为：

(u，v)为原始图像像素坐标，(x=x'/w'，y=y'/w')为变换之后的图像像素坐标。透视变换矩阵图解如下：

仿射变换(Affine Transformation)可以理解为透视变换的特殊形式。透视变换的数学表达式为：

所以，给定透视变换对应的四对像素点坐标，即可求得透视变换矩阵；反之，给定透视变换矩阵，即可对图像或像素点坐标完成透视变换，如下图所示：

2. OpenCV透视变换函数

Mat getPerspectiveTransform(const Point2f* src, const Point2f* dst)

// Calculate a perspective transform from four pairs of the corresponding points.

// src – Coordinates of quadrangle vertices in the source image.

// dst – Coordinates of the corresponding quadrangle vertices in the destination image.

void warpPerspective(InputArray src, OutputArray dst, InputArray M, Size dsize, int flags=INTER_LINEAR, int borderMode=BORDER_CONSTANT, const Scalar& borderValue=Scalar())

// Apply a perspective transform to an image.

// src – Source image.

// dst – Destination image that has the size dsize and the same type as src.

// M – 3*3 transformation matrix.

// dsize – Size of the destination image.

// flags – Combination of interpolation methods and the optional flag WARP_INVERSE_MAP that means that M is the inverse transformation (dstsrc).

// borderMode – Pixel extrapolation method. When borderMode=BORDER_TRANSPARENT, it means that the pixels in the destination image that corresponds to the “outliers” in the source image are not modified by the function.

// borderValue – Value used in case of a constant border. By default, it is 0.

3. 程序

#include

#include "highgui.h"

#include "opencv2/imgproc/imgproc.hpp"

int main()

{

// get original image.

cv::Mat originalImage = cv::imread("road.png");

// perspective image.

cv::Mat perspectiveImage;

// perspective transform

cv::Point2f objectivePoints[4], imagePoints[4];

// original image points.

imagePoints[0].x = 10.0; imagePoints[0].y = 457.0;

imagePoints[1].x = 395.0; imagePoints[1].y = 291.0;

imagePoints[2].x = 624.0; imagePoints[2].y = 291.0;

imagePoints[3].x = 1000.0; imagePoints[3].y = 457.0;

// objective points of perspective image.

// move up the perspective image : objectivePoints.y - value .

// move left the perspective image : objectivePoints.x - value.

double moveValueX = 0.0;

double moveValueY = 0.0;

objectivePoints[0].x = 46.0 + moveValueX; objectivePoints[0].y = 920.0 + moveValueY;

objectivePoints[1].x = 46.0 + moveValueX; objectivePoints[1].y = 100.0 + moveValueY;

objectivePoints[2].x = 600.0 + moveValueX; objectivePoints[2].y = 100.0 + moveValueY;

objectivePoints[3].x = 600.0 + moveValueX; objectivePoints[3].y = 920.0 + moveValueY;

cv::Mat transform = cv::getPerspectiveTransform(objectivePoints, imagePoints);

// perspective.

cv::warpPerspective(originalImage,

perspectiveImage,

transform,

cv::Size(originalImage.rows, originalImage.cols),

cv::INTER_LINEAR | cv::WARP_INVERSE_MAP);

// cv::imshow("perspective image", perspectiveImage);

// cvWaitKey(0);

cv::imwrite("perspectiveImage.png", perspectiveImage);

return 0;

}

原始图像及其透视变换结果：

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。

时间： 2019-05-20