Fast Contour-Tracing Algorithm c#

LOVE love me answered on May 16, 2022 Popularity 1/10 Helpfulness 1/10

answer Fast Contour-Tracing Algorithm c#

Fast Contour-Tracing Algorithm c#

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pixel * mooreNeighborTracing(pixel * image, int width, int height)
{
  bool inside = false;
  int pos = 0;
 
  // Need to start by padding the image by 1 pixel
  pixel * paddedImage = padImage(image, width, height, WHITE);
 
  // Allocate new image as a 1D array
  pixel * borderImage = (pixel *)malloc(sizeof(pixel) * (height+2) * (width+2));
 
  // Set entire image to WHITE
  for(int y = 0; y < (height+2); y ++)
  {
    for(int x = 0; x < (width+2); x ++)
    {
      borderImage[x + y*(width+2)] = WHITE;
    }
  }
 
  for(int y = 0; y < (height+2); y ++)
  {
    for(int x = 0; x < (width+2); x ++)
    {
      pos = x + y*(width+2);
 
      // Scan for BLACK pixel
      if(borderImage[pos] == BLACK && !inside)    // Entering an already discovered border
      {
        inside = true;
      }
      else if(paddedImage[pos] == BLACK && inside)  // Already discovered border point
      {
        continue;
      }
      else if(paddedImage[pos] == WHITE && inside)  // Leaving a border
      {
        inside = false;
      }
      else if(paddedImage[pos] == BLACK && !inside)  // Undiscovered border point
      {
        borderImage[pos] = BLACK;   // Mark the start pixel
        int checkLocationNr = 1;  // The neighbor number of the location we want to check for a new border point
        int checkPosition;      // The corresponding absolute array address of checkLocationNr
        int newCheckLocationNr;   // Variable that holds the neighborhood position we want to check if we find a new border at checkLocationNr
        int startPos = pos;      // Set start position
        int counter = 0;       // Counter is used for the jacobi stop criterion
        int counter2 = 0;       // Counter2 is used to determine if the point we have discovered is one single point
 
        // Defines the neighborhood offset position from current position and the neighborhood
        // position we want to check next if we find a new border at checkLocationNr
        int neighborhood[8][2] = {
            {-1,7},
            {-3-width,7},
            {-width-2,1},
            {-1-width,1},
            {1,3},
            {3+width,3},
            {width+2,5},
            {1+width,5}
          };
        // Trace around the neighborhood
        while(true)
        {
          checkPosition = pos + neighborhood[checkLocationNr-1][0];
          newCheckLocationNr = neighborhood[checkLocationNr-1][1];
 
          if(paddedImage[checkPosition] == BLACK) // Next border point found
          {
            if(checkPosition == startPos)
            {
              counter ++;
 
              // Stopping criterion (jacob)
              if(newCheckLocationNr == 1 || counter >= 3)
              {
                // Close loop
                inside = true; // Since we are starting the search at were we first started we must set inside to true
                break;
              }
            }
 
            checkLocationNr = newCheckLocationNr; // Update which neighborhood position we should check next
            pos = checkPosition;
            counter2 = 0;             // Reset the counter that keeps track of how many neighbors we have visited
            borderImage[checkPosition] = BLACK; // Set the border pixel
          }
          else
          {
            // Rotate clockwise in the neighborhood
            checkLocationNr = 1 + (checkLocationNr % 8);
            if(counter2 > 8)
            {
              // If counter2 is above 8 we have traced around the neighborhood and
              // therefor the border is a single black pixel and we can exit
              counter2 = 0;
              break;
            }
            else
            {
              counter2 ++;
            }
          }
        }
      }
    }
  }
 
  // Remove white padding and return it
  pixel * clippedBorderImage = (pixel *)malloc(sizeof(pixel) * (height) * (width));
  for(int x = 0; x < width; x ++)
  {
    for(int y = 0; y < height; y ++)
    {
      clippedBorderImage[x+y*width] = borderImage[x+1+(y+1)*(width+2)];
    }
  }
  return clippedBorderImage;
}

Popularity 1/10 Helpfulness 1/10 Language csharp

Source: www.eriksmistad.no

Tags: algorithm c#

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Contributed on May 16 2022

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Fast Contour-Tracing Algorithm c#

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