使用Opencv调整大小/裁剪图像

Question

I'm new to OpenCV and was hoping to get help on a project I'm working on. I want to separate the foreground from the background and resizing / cropping the original image so that the foreground fits.

I have this sample, and i would like to be able to get an optimal result like this:

Before

After

Answer 1

a simple code just to give an idea. it works fine for images like yours.

(note: i used this code partly)

#include "opencv2/opencv.hpp"

using namespace cv;
using namespace std;

int main( int argc, char** argv )
{
    int largest_area=0;
    int largest_contour_index=0;
    cv::Rect bounding_rect;

    Mat src = imread(argv[1]);
    Mat edges;

    cvtColor( src, edges, COLOR_BGR2GRAY ); //Convert to gray
    GaussianBlur(edges, edges, Size(7,7), 1.5, 1.5);
    Canny(edges, edges, 0, 50, 3);
    dilate(edges,edges,Mat(),Point(-1,-1),3);
    erode(edges,edges,Mat(),Point(-1,-1),3);

    vector<vector<cv::Point> > contours; // Vector for storing contour

    findContours( edges, contours,CV_RETR_CCOMP, CV_CHAIN_APPROX_SIMPLE ); // Find the contours in the image

    for( int i = 0; i< contours.size(); i++ ) // iterate through each contour.
    {
        double a=contourArea( contours[i],false);  //  Find the area of contour
        if(a>largest_area)
        {
            largest_area=a;
            largest_contour_index=i;                //Store the index of largest contour
            bounding_rect=boundingRect(contours[i]); // Find the bounding rectangle for biggest contour
        }
    }

    // ------------
    // makes border
    bounding_rect.x -= 10;
    bounding_rect.y -= 10;
    bounding_rect.width += 20;
    bounding_rect.height += 20;
    bounding_rect = Rect(0,0,src.cols,src.rows) & bounding_rect;
    // ------------

    Mat biggest_contour_rect = src( bounding_rect ).clone();
    imshow("biggest_contour_rect", biggest_contour_rect );
    waitKey(0);
    return 0;
}