Seeking the shortest path of the picture 2 Detailed explanation of the Dijkstra algorithm Eric

2023-03-14  

CvMemStorage
CvMemStorage *storage=cvCreateMemStorage(block_size);
Use to create a memory memory to uniformly manage the memory of various dynamic objects.

The

function returns a newly created memory memory pointer.

The

parameter block_size corresponds to the size of each memory block in the memory device, and the default size of the memory block is 64K.
strcmp
extern int strcmp(const char *s1，const char * s2)；
When S1 <s2, return to the negative number is not -1
When S1 == S2, the return value = 0
When S1> S2, return to the positive number is not 1
cvFindContours
Retrieves the contour from the dual -value image and returns the number of outline detected. The value of the first_contour is returned by the function, and its value will be the first outer contour
pointer
, null when the outline was detected. Other outlines can be connected to H_next and v_next to reach the first_contour.

int cvFindContours(          CvArr* image,      CvMemStorage* storage,       CvSeq** first_contour,
                                            int header_size=sizeof(CvContour),              int mode=CV_RETR_LIST,
                                            int method=CV_CHAIN_APPROX_SIMPLE,        CvPoint offset=cvPoint(0,0)          );
image
8 BitSingle -channel source dual -value image. Non -zero pixels are treated as 1, 0 pixel preservation remains unchanged. From a
gray image
The function of the second -value image is:
cvThreshold
, CVADAPTIVETHRSHOLD and
cvCanny
。
storage
Return to container.
first_contour
output parameters are used to store the first external contour.
header_size
The size of the sequence of the sequence. If you select the method = cv_chain_code, the header_size> = sizeof (cvchain);

The

header_size >= sizeof(CvContour)。
mode
retrieval mode can be taken as follows:
cv_retr_external: only retrieve the outermost contour;
cv_retr_list: retrieve all outlines and put them in list;
cv_retr_ccomp: Retrieve all outlines and organize them into two layers: the top layer is the external boundary of each part, and the second layer is the empty boundary;
cv_retr_tree: Retrieve all outlines and reconstruct the entire level of nested outline.
blue indicates v_next, green represents h_next
method
Edge approximation method (except that CV_RETR_RUNS uses built -in approximation, other modes use the approximate algorithm of this setting). The value can be taken as follows:
cv_chain_code: with freeman
chain code

The
method outputs outline, and all other methods output polygon (sequence of the vertex).

cv_chain_approx_none: Convert all the consecutive codes into points.
cv_chain_approx_simple: The compressed level, vertical, and oblique parts, that is, the function only retains their end point.
cv_chain_approx_tc89_L1, CV_Chain_APPROX_TC89_KCOS: Use The Flavors of Teh-Chin Chain

One of

.
CV_LINK_RUNS: By connecting the horizontal segment 1, use a completely different edge extraction algorithm. This method can be used using the CV_RETR_LIST search mode.
offset
offset
, used to move all outline points. When the contour is from
image

The
ROI extraction and need to be analyzed in the entire image. This parameter will be useful.

cvDrawContours：
CVDRAWCONTORS inimageDraw external and internal contour on the inside. When Thickness> = 0, draw the contour line; otherwise the part surrounded by the contour is filled.
void cvDrawContours(     CvArr *img,           CvSeq* contour,
                                                 CvScalar external_color,       CvScalar hole_color,
                                                 int max_level,            int thickness=1,
                                                 int line_type=8,         CvPoint offset=cvPoint(0,0)   );
img
The image of the contour is drawn on it. As in other drawing functions, the contour is the pruning result of ROI.
contour
point to the first outlinepointer。
external_color
outer contour color.
hole_color
Inner contour color.
max_level
Draw the maximum number of outlines. If it is 0, only draw Contour; if it is 1, all outlines of the same layer as Contour will be drawn; if it is 2, all the same layer and low -layer outlines after drawing are drawn, and so on; if the value is negative value, the value is negative value. The function does not draw the contour after the contour is drawn, but it will draw the subtitle until the ABS (MAX_LEVEL) -1 layer.
thickness
Draw the width of the contour line. If it is negative (for example, equal to cv_filled), the contour will be drawn inside.

The type of

line_type
contour segment, specifically check the description of CVLINE.
offset
Move all points at the given value to all points
Example results:
Program:

#include “cv.h”
#include “cxcore.h”
#include “highgui.h”
 
int main( int argc, char** argv )
{

// State the iPLIMAGE pointer
  IplImage* pImg = NULL;
  IplImage* pContourImg = NULL;
 
 
CVMEMSTORAGE * Storage = cvcreateMemstorage (0); // Create memory block size is 64K
  CvSeq * contour = 0;
 int mode = CV_RETR_EXTERNAL;

if( argc == 3)
    if(strcmp(argv[2], “all”) == 0)
mode = cv_retr_ccomp; // Internal and external outlines are detected
 
 
// Create a window
  cvNamedWindow(“src”, 1);
  cvNamedWindow(“contour”,1);
 
 
// Load the image and force the transformation to Gray
 if( (pImg = cvLoadImage( “E:\\Lena.jpg”, 0)) != 0 )
    {

      cvShowImage( “src”, pImg );
// For the outline display image application space

// 3 channel images in order to display in color
      pContourImg = cvCreateImage(cvGetSize(pImg),IPL_DEPTH_8U,3);
// Copy the original image and convert it to BGR image
      cvCvtColor(pImg, pContourImg, CV_GRAY2BGR);
 
// Find Contour
      cvFindContours( pImg, storage, &contour, sizeof(CvContour),
    mode, CV_CHAIN_APPROX_SIMPLE, cvPoint(0,0));
 
    }
  else
    {

// Destruction window
      cvDestroyWindow( “src” );
      cvDestroyWindow( “contour” );
      cvReleaseMemStorage(&storage);
 
      return -1;
    }
 
// Draw out outline
CVDRAWCONTOURS (PContourimg, Contour, // The former is an image, the latter is a pointer pointed to the first outline
CV_RGB (0,0,255), CV_RGB (255, 0, 0), // outer contour blue, inner contour red
2, 2, 8, CVPOINT (0,0)); // All the same layer and low -level outline after drawing contour, so on, the line width is 2, the line segment type is 8, the offset coordinates are (the offset coordinates ( 0, 0)
// Display images
  cvShowImage( “contour”, pContourImg );
 
  cvWaitKey(0);
 
// Destruction window
  cvDestroyWindow( “src” );
  cvDestroyWindow( “contour” );
// Release images
  cvReleaseImage( &pImg );
  cvReleaseImage( &pContourImg );
  cvReleaseMemStorage(&storage);
  return 0;
}

source

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