Esempio n. 1
0
  public void run(ImageProcessor image) {
    /**
     * ********************************************************************************* Initial
     * phase *********************************************************************************
     */
    int width = image.getWidth();
    int heigh = image.getHeight();
    ByteProcessor bp = Service.getByteProcessor(image);

    /**
     * ********************************************************************************* Convolve
     * with LoG kernel
     * *********************************************************************************
     */
    Convolver convolver = new Convolver();
    convolver.setNormalize(false);
    convolver.convolve(bp, log, (int) Math.sqrt(log.length), (int) Math.sqrt(log.length));
    ImagePlus outImg = new ImagePlus("Later Log kernel", bp);
    outImg.show();

    /**
     * ********************************************************************************* threshold
     * *********************************************************************************
     */
    ByteProcessor bpThreshold = Service.getByteProcessor(bp);
    int lut[] = new int[256];
    int i = 0;
    for (; i < threshold; i++) lut[i] = 0;
    for (int j = i; j < lut.length; j++) lut[j] = 255;
    bpThreshold.applyTable(lut);
    ImagePlus outImg1 = new ImagePlus("Later threshold phase", bpThreshold);
    outImg1.show();

    /**
     * ********************************************************************************* Find Zero
     * crossing *********************************************************************************
     */
    ByteProcessor out = new ByteProcessor(width, heigh);
    for (i = 0; i < width; i++) for (int j = 0; j < heigh; j++) out.set(i, j, 255);
    for (int x = 0; x < width - 1; x++) {
      for (int y = 0; y < heigh - 1; y++) {
        if (bpThreshold.get(x, y) != bpThreshold.get(x, y + 1)) out.set(x, y, 0);
        if (bpThreshold.get(x, y) != bpThreshold.get(x + 1, y)) out.set(x, y, 0);
        if (bpThreshold.get(x, y) != bpThreshold.get(x + 1, y + 1)) out.set(x, y, 0);
      }
    }
    ImagePlus outImg2 = new ImagePlus("Edge Find", out);
    outImg2.show();
  }
  public void run(ImageProcessor ip) {
    int w = ip.getWidth(); // Get width of image
    int h = ip.getHeight(); // Get height of image

    /**
     * ------------------------------------------------------------------ BEGIN PRELIMINARY STEPS
     * ------------------------------------------------------------------*
     */

    /**
     * ----------------------------------- BEGIN: CREATE IMAGES THAT WILL BE USED IN COMPUTATIONS
     * -----------------------------------*
     */
    // Create the smoothed image to be used for the different edge images
    ImageProcessor Smoothed_Ip_xf = new FloatProcessor(w, h);
    ImageProcessor Smoothed_Ip_yf = new FloatProcessor(w, h);
    ImageProcessor Smoothed_Ip_45f = new FloatProcessor(w, h);
    ImageProcessor Smoothed_Ip_135f = new FloatProcessor(w, h);

    // Create the edge image detecting vertical edges
    ImageProcessor G_xf_Ip = new FloatProcessor(w, h);

    // Create the edge image detecting horizontal edges
    ImageProcessor G_yf_Ip = new FloatProcessor(w, h);

    // Create the edge image detecting 135 degree edges
    ImageProcessor G_45f_Ip = new FloatProcessor(w, h);

    // Create the edge image detecting 45 degree edges
    ImageProcessor G_135f_Ip = new FloatProcessor(w, h);

    // Create the gradient magnitude image
    ImageProcessor GMag_Ip = new ByteProcessor(w, h); // Byte version
    ImageProcessor GMagf_Ip = new FloatProcessor(w, h); // Floating point version

    // Create the gradient direction image
    ImageProcessor GDir_Ip = new ByteProcessor(w, h); // Byte version
    ImageProcessor GDirf_Ip = new FloatProcessor(w, h); // Floating point version

    // Create the edge image (output from non-maximal suppression)
    ImageProcessor Edge_Ip = new ByteProcessor(w, h); // Byte Version
    Edge_Ip.setValue(0); // 0 = Black
    Edge_Ip.fill(); // Fill Edge_Ip all black

    ImageProcessor Copy_Edge_Ip = new ByteProcessor(w, h); // Byte Version
    Copy_Edge_Ip.setValue(0); // 0 = Black
    Copy_Edge_Ip.fill(); // Fill Edge_Ip all black

    ImageProcessor Edgef_Ip = new FloatProcessor(w, h); // Floating Point version
    Edgef_Ip.setValue(0); // 0 = Black
    Edgef_Ip.fill(); // Fill Edge_Ip all black

    ImageProcessor Copy_Edgef_Ip = new FloatProcessor(w, h); // Floating Point version
    Copy_Edgef_Ip.setValue(0); // 0 = Black
    Copy_Edgef_Ip.fill(); // Fill Edge_Ip all black

    // Create the Threshold with Hysteresis image
    ImageProcessor Threshold_Ip = new ByteProcessor(w, h);
    Threshold_Ip.setValue(0); // 0 = Black
    Threshold_Ip.fill(); // Fill Edge_Ip all black
    /**
     * ----------------------------------- END: CREATE IMAGES THAT WILL BE USED IN COMPUTATIONS
     * -----------------------------------*
     */

    /**
     * ----------------------------------------------------- BEGIN: USER INPUT
     * -----------------------------------------------------*
     */
    double STDDev = 0,
        TLow = 0,
        THigh =
            0; // Declare and initialize variables for the standard deviation, low threshold, and
               // high threshold
    int Size = 0; // Initialize size of Gaussian Filter
    boolean EdgeStrengthImage; // specifies whether edge strength image should be shown
    GenericDialog gd = new GenericDialog("User Inputs");
    gd.addNumericField(
        "Size of Gaussian Filter (Odd Integer)", Size, 0); // Field for Size of Gaussian Filter
    gd.addNumericField("Standard Deviation", STDDev, 0); // Field for Standard Deviation
    gd.addNumericField("Low Threshold (1 - 255)", TLow, 0); // Field for Low Threshold
    gd.addNumericField("High Threshold (1 - 255)", THigh, 0); // Field for High Threshold
    gd.showDialog();
    if (gd.wasCanceled()) {
      return;
    } else {
      Size =
          (int)
              gd
                  .getNextNumber(); // Set Size variable from user input. This allows the user to
                                    // set the size of the Gaussian Filter
      STDDev = gd.getNextNumber(); // Set STDDev variable from user input
      TLow = gd.getNextNumber(); // Set TLow variable from user input
      THigh = gd.getNextNumber(); // Set THigh variable from user input
    }

    /**
     * ----------------------------------------------------- END: USER INPUT
     * -----------------------------------------------------*
     */

    /**
     * ------------------------------------------------------------------ END PRELIMINARY STEPS
     * ------------------------------------------------------------------*
     */

    /**
     * ------------------------------------------------------------------ BEGIN CANNY EDGE DETECTION
     * ------------------------------------------------------------------*
     */

    /**
     * ----------------------------------------------------- BEGIN STEP 1: NOISE REDUCTION VIA
     * GAUSSIAN ----------------------------------------------------- *
     */
    ImageProcessor ipf = ip.convertToFloat(); // Convert original image to floating point
    int SizeSquared = (int) Math.pow(Size, 2); // Square the size of Gaussian Kernel
    int HalfSize = (Size - 1) / 2; // Cut the size of the Gaussian Kernel almost in half
    float pix; // Temporary storage to be used throughout code to store pixel values
    float[] GaussianFilter =
        new float[SizeSquared]; // Initialize Gaussian Filter to be used in the convolution
    double[] GaussianFilterD =
        new double
            [SizeSquared]; // Initialize Gaussian Filter to be used...this filter will be composed
                           // of numbers of type double
    double Constant = 1 / (2 * Math.PI * Math.pow(STDDev, 2)); // Compute 1/(2*pi*sigma^2)
    double ExponentDenom = 2 * Math.pow(STDDev, 2); // Compute 2*sigma^2
    double Value; // Temporary storage to store the computations that will form the Gaussian Filter

    // FOR LOOP TO FORM GaussianFilterD
    for (int i = 0; i < Size; i++) {
      for (int j = 0; j < Size; j++) {
        Value =
            Math.exp(
                -1
                    * (Math.pow(j - HalfSize, 2) + Math.pow(i - HalfSize, 2))
                    / (ExponentDenom)); // Set Value = e^(-(i^2 + j^2)/(2*sigma^2))
        GaussianFilterD[Size * i + j] = Constant * Value; // Place Value in GaussianFilterD
      }
    }

    // FOR LOOP TO FORM GaussianFilter using GaussianFilterD
    for (int i = 0; i < Math.pow(Size, 2); i++) {
      GaussianFilter[i] = (float) GaussianFilterD[i]; // Convert double values to float one by one
    }

    // CONVOLVE IMAGE WITH GAUSSIAN
    Convolver cv = new Convolver(); // Create the convolver
    cv.setNormalize(true); // Normalize the filter
    cv.convolve(
        ipf,
        GaussianFilter,
        Size,
        Size); // Apply the GaussianFilter using convolution on the image ipf

    // For loop to create 4 smoothed images to be used in detecting the 4 edges: 0 deg, 45 deg, 90
    // deg, 135 deg
    for (int i = 0; i < w; i++) {
      for (int j = 0; j < h; j++) {
        pix = ipf.getf(i, j);
        Smoothed_Ip_xf.setf(
            i, j,
            pix); // Smoothed image to convolve with Sobel filter in x-direction (detects vertical
                  // edges)
        Smoothed_Ip_yf.setf(
            i, j,
            pix); // Smoothed image to convolve with Sobel filter in y-direction (detects horizontal
                  // edges)
        Smoothed_Ip_45f.setf(
            i, j,
            pix); // Smoothed image to convolve with Sobel filter in 45 degree direction (detects
                  // 135 degree edges)
        Smoothed_Ip_135f.setf(
            i, j,
            pix); // Smoothed image to convolve with Sobel filter in 135 degree direction (detects
                  // 45 degree edges)
      }
    }

    /**
     * ----------------------------------------------------- END STEP 1: NOISE REDUCTION VIA
     * GAUSSIAN ----------------------------------------------------- *
     */

    /**
     * ----------------------------------------------------- BEGIN STEP 2: COMPUTE GRADIENT
     * MAGNITUDE AND DIRECTION IMAGES ----------------------------------------------------- *
     */

    // Sobel Filters to detect edges
    float[] G_x = {-1, 0, 1, -2, 0, 2, -1, 0, 1}; // Sobel operator in x direction
    float[] G_y = {-1, -2, -1, 0, 0, 0, 1, 2, 1}; // Sobel operator in y direction
    float[] G_135 = {2, 1, 0, 1, 0, -1, 0, -1, -2}; // Sobel operator in 135 degree direction
    float[] G_45 = {0, 1, 2, -1, 0, 1, -2, -1, 0}; // Sobel operator in 45 degree direction

    // CONVOLVE IMAGE USING SOBEL FILTERS
    cv.convolve(
        Smoothed_Ip_xf,
        G_x,
        3,
        3); // Apply the Sobel filter in x-direction using convolution on the smoothed image
    cv.convolve(
        Smoothed_Ip_yf,
        G_y,
        3,
        3); // Apply the Sobel filter in y-direction using convolution on the smoothed image
    cv.convolve(
        Smoothed_Ip_45f,
        G_45,
        3,
        3); // Apply the Sobel filter in 45 degree direction using convolution on the smoothed image
    cv.convolve(
        Smoothed_Ip_135f,
        G_135,
        3,
        3); // Apply the Sobel filter in 135 degree direction using convolution on the smoothed
            // image

    // For loop to define the 4 floating point images G_xf_Ip, G_yf_Ip, G_45f_Ip, G_135f_Ip
    for (int i = 0; i < w; i++) {
      for (int j = 0; j < h; j++) {
        pix = Smoothed_Ip_xf.getf(i, j);
        G_xf_Ip.setf(i, j, pix);
        pix = Smoothed_Ip_yf.getf(i, j);
        G_yf_Ip.setf(i, j, pix);
        pix = Smoothed_Ip_45f.getf(i, j);
        G_45f_Ip.setf(i, j, pix);
        pix = Smoothed_Ip_135f.getf(i, j);
        G_135f_Ip.setf(i, j, pix);
      }
    }

    // COMPUTE THE GRADIENT MAGNITUDE IMAGE GMagf_Ip
    float pix1, pix2; // Variables to store pixel values of G_xf_Ip and G_yf_Ip
    for (int i = 0; i < w; i++) {
      for (int j = 0; j < h; j++) {
        pix1 = G_xf_Ip.getf(i, j); // Get pixel value
        pix2 = G_yf_Ip.getf(i, j); // Get Pixel Value
        pix =
            (float)
                Math.sqrt(
                    pix1 * pix1
                        + pix2
                            * pix2); // Take the square root of the sum of the squares of both pixel
                                     // values
        GMagf_Ip.setf(
            i, j, 255 * pix); // Place in (i,j) position of GMagf_Ip and scale by 255 to view
      }
    }

    // COMPUTE THE GRADIENT DIRECTION IMAGE
    double v1, v2, v3, v4; // Temporary storage for the abs. value of pixel vlaues
    int pixi; // Temporary storage for pixel values
    double[][] GDir =
        new double[h]
            [w]; // Define 2D Array to store gradient direction values. Will use this during Step 3
                 // Non-Maximal Suppression instead of the gradient direction image

    // For loop to compute gradient direction image
    for (int i = 0; i < w; i++) {
      for (int j = 0; j < h; j++) {
        // Obtain the absolute value of each pixel in the following four floating point images
        v1 = Math.abs(G_xf_Ip.getf(i, j));
        v2 = Math.abs(G_yf_Ip.getf(i, j));
        v3 = Math.abs(G_45f_Ip.getf(i, j));
        v4 = Math.abs(G_135f_Ip.getf(i, j));

        // If statements to find the maximal response (strongest edge direction)

        if (v1 > v2 && v1 > v3 && v1 > v4) // Vertical edge orientation
        {
          GDir_Ip.putPixel(i, j, 0);
          GDir[j][i] = 0; // 0 stands for vertical edge orientation
        } else if (v3 > v1 && v3 > v2 && v3 > v4) // 45 degree edge orientation
        {
          GDir_Ip.putPixel(i, j, 1);
          GDir[j][i] = 1; // 1 stands for 45 degree edge orientation
        } else if (v2 > v1 && v2 > v3 && v2 > v4) // Horizontal edge orientation
        {
          GDir_Ip.putPixel(i, j, 2);
          GDir[j][i] = 2; // 2 stands for horizontal edge orientation
        } else if (v4 > v1 && v4 > v2 && v4 > v3) // 135 degree edge orientation
        {
          GDir_Ip.putPixel(i, j, 3);
          GDir[j][i] = 3; // 3 stands for 135 degree edge orientation
        }

        pixi =
            (int) (255.0 / 3.0)
                * GDir_Ip.getPixel(
                    i, j); // Scale the gradient direction image so we can actually see it
        GDir_Ip.putPixel(
            i, j,
            pixi); // Place pixi in the (i,j) location of GDir_Ip...we can now view the gradient
                   // direction image
      }
    }

    // OUTPUT GRADIENT DIRECTION IMAGE
    String DirTitle = "Gradient Direction";
    ImagePlus GDir_Im = new ImagePlus(DirTitle, GDir_Ip);
    GDir_Im.show();

    // OUTPUT GRADIENT MAGNITUDE IMAGE (need to convert to ByteProcessor to view first)
    GMagf_Ip.resetMinAndMax();
    GMag_Ip.insert(GMagf_Ip.convertToByte(true), 0, 0);

    String MagTitle = "Gradient Magnitude";
    ImagePlus GMag_Im = new ImagePlus(MagTitle, GMag_Ip);
    GMag_Im.show();

    /**
     * ----------------------------------------------------- BEGIN STEP 2: COMPUTE GRADIENT
     * MAGNITUDE AND DIRECTION IMAGES ----------------------------------------------------- *
     */

    /**
     * ----------------------------------------------------- BEGIN STEP 3: NON-MAXIMAL SUPPRESSION
     * -----------------------------------------------------*
     */
    // Ignoring boundaries for convenience
    float Magnitude; // Storage for magnitude
    double Direction; // Storage for direction

    // FOR LOOP TO COMPUTE NON-MAXIMAL SUPPRESSION IMAGE
    for (int i = 1; i < w - 1; i++) {
      for (int j = 1; j < h - 1; j++) {
        Magnitude =
            GMagf_Ip.getf(
                i, j); // Get the magnitude in the (i,j) position of the gradient magnitude image

        if (Magnitude != 0) // If the magnitude is non-zero then we find the direction of the edge
        {
          Direction = GDir[j][i]; // Obtain the direction
          float n1GradMag = 0,
              n2GradMag = 0; // Initialize storage for the magnitude of the 2 neighboring pixels

          if (Direction
              == 0) // If Direction is 0 get the magnitude in the columns to the left and right
          {
            n1GradMag = GMagf_Ip.getf(i - 1, j);
            n2GradMag = GMagf_Ip.getf(i + 1, j);
          } else if (Direction
              == 1) // If Direction is 45 degree get the magnitude in adjacent pixels
          {
            n1GradMag = GMagf_Ip.getf(i + 1, j - 1);
            n2GradMag = GMagf_Ip.getf(i - 1, j + 1);
          } else if (Direction
              == 2) // If Direction is 2 get the magnitude in the rows above and below
          {
            n1GradMag = GMagf_Ip.getf(i, j - 1);
            n2GradMag = GMagf_Ip.getf(i, j + 1);
          } else if (Direction
              == 3) // If Direction is 135 degrees get the magnitude in adjacent pixels
          {
            n1GradMag = GMagf_Ip.getf(i - 1, j - 1);
            n2GradMag = GMagf_Ip.getf(i + 1, j + 1);
          }

          if (Magnitude > n1GradMag
              && Magnitude
                  > n2GradMag) // Check to see if the magnitude of pixel under inspection is the
                               // largest relative to its adjacent pixels
          {
            pix = GMagf_Ip.getf(i, j); // Store magnitude in (i,j) position in pix variable
            Edgef_Ip.setf(
                i, j,
                pix); // Place this pixel value in the (i,j) position of Edge Image (Edge Image is
                      // output from non-maximal suppression)
            Copy_Edgef_Ip.setf(
                i, j,
                pix); // Place this pixel value in the (i,j) position of Copy Edge Image (this will
                      // be used for thresholding with hysteresis)

          } else {
          } // Else do nothing since edge image was already filled with 0's at beginning of code
        } else {
        } // Do nothing if magnitude is 0
      }
    }

    Copy_Edgef_Ip.resetMinAndMax();
    Copy_Edge_Ip.insert(Copy_Edgef_Ip.convertToByte(true), 0, 0);

    // Display edge magnitude image but we need to convert to ByteProcessor first
    Edgef_Ip.resetMinAndMax();
    Edge_Ip.insert(Edgef_Ip.convertToByte(true), 0, 0);

    String cTitle = "Non-Maximal Suppression";
    ImagePlus Edge_Im = new ImagePlus(cTitle, Edge_Ip);
    Edge_Im.show();
    /**
     * ----------------------------------------------------- END STEP 3: NON-MAXIMAL SUPPRESSION
     * -----------------------------------------------------*
     */

    /**
     * ----------------------------------------------------- BEGIN STEP 4: THRESHOLDING WITH
     * HYSTERESIS -----------------------------------------------------*
     */
    int count = 0; // Initialize counter to be used in while loop
    int IterationCount = 500; // Number of iterations to perform

    // Scan through all pixels in the edge image and mark all edges with magnitude above the high
    // threshold as a true edge otherwise if the magnitude is below the low threshold
    // then we delete that pixel (set it to zero)
    for (int i = 0; i < w; i++) {
      for (int j = 0; j < h; j++) {
        Magnitude = Copy_Edge_Ip.getPixel(i, j); // Obtain magnitude in edge image

        if (Magnitude
            > THigh) // If Magnitude is larger than the high threshold then make pixel white
        {
          Threshold_Ip.putPixel(i, j, 255); // True edge (Updates Threshold image to be output)
          Copy_Edge_Ip.putPixel(
              i, j,
              255); // True edge (Updates edge image which will be used in the iterative
                    // thresholding)
        } else if (Magnitude
            < TLow) // Else if magnitude is below the low threshold then make pixel black
        {
          Threshold_Ip.putPixel(i, j, 0); // Not an edge (Updates Threshold image to be output)
          Copy_Edge_Ip.putPixel(
              i, j,
              0); // Not an edge (Updates edge image which will be used in the iterative
                  // thresholding)
        }
      }
    }

    while (count < IterationCount) // Iterate again and again
    {
      // Ignore boundary pixels for convenience
      for (int i = 1; i < w - 1; i++) {
        for (int j = 1; j < h - 1; j++) {
          Magnitude = Copy_Edge_Ip.getPixel(i, j); // Obtain magnitude in edge image
          if (Magnitude == 255) // If we reach a true edge then we look at its 8 neighbors
          {
            // Obtain the magnitude in the 8 neighbors
            int n1, n2, n3, n4, n5, n6, n7, n8;
            n1 = Copy_Edge_Ip.getPixel(i - 1, j);
            n2 = Copy_Edge_Ip.getPixel(i - 1, j - 1);
            n3 = Copy_Edge_Ip.getPixel(i, j - 1);
            n4 = Copy_Edge_Ip.getPixel(i + 1, j - 1);
            n5 = Copy_Edge_Ip.getPixel(i + 1, j);
            n6 = Copy_Edge_Ip.getPixel(i + 1, j + 1);
            n7 = Copy_Edge_Ip.getPixel(i, j + 1);
            n8 = Copy_Edge_Ip.getPixel(i - 1, j + 1);
            if (n1
                >= TLow) // If n1 is greater than or equal to the low threshold then we mark it as
                         // an edge
            {
              Copy_Edge_Ip.putPixel(i - 1, j, 255); // Update edge image
              Threshold_Ip.putPixel(
                  i - 1, j,
                  255); // Update threshold image (This is the output image from thresholding with
                        // hysteresis)
            }
            if (n2
                >= TLow) // If n2 is greater than or equal to the low threshold then we mark it as
                         // an edge
            {
              Copy_Edge_Ip.putPixel(i - 1, j - 1, 255); // Update edge image
              Threshold_Ip.putPixel(
                  i - 1, j - 1,
                  255); // Update threshold image (This is the output image from thresholding with
                        // hysteresis)
            }
            if (n3
                >= TLow) // If n3 is greater than or equal to the low threshold then we mark it as
                         // an edge
            {
              Copy_Edge_Ip.putPixel(i, j - 1, 255); // Update edge image
              Threshold_Ip.putPixel(
                  i, j - 1,
                  255); // Update threshold image (This is the output image from thresholding with
                        // hysteresis)
            }
            if (n4
                >= TLow) // If n4 is greater than or equal to the low threshold then we mark it as
                         // an edge
            {
              Copy_Edge_Ip.putPixel(i + 1, j - 1, 255); // Update edge image
              Threshold_Ip.putPixel(
                  i + 1, j - 1,
                  255); // Update threshold image (This is the output image from thresholding with
                        // hysteresis)
            }
            if (n5
                >= TLow) // If n5 is greater than or equal to the low threshold then we mark it as
                         // an edge
            {
              Copy_Edge_Ip.putPixel(i + 1, j, 255); // Update edge image
              Threshold_Ip.putPixel(
                  i + 1, j,
                  255); // Update threshold image (This is the output image from thresholding with
                        // hysteresis)
            }
            if (n6
                >= TLow) // If n6 is greater than or equal to the low threshold then we mark it as
                         // an edge
            {
              Copy_Edge_Ip.putPixel(i + 1, j + 1, 255); // Update edge image
              Threshold_Ip.putPixel(
                  i + 1, j + 1,
                  255); // Update threshold image (This is the output image from thresholding with
                        // hysteresis)
            }
            if (n7
                >= TLow) // If n7 is greater than or equal to the low threshold then we mark it as
                         // an edge
            {
              Copy_Edge_Ip.putPixel(i, j + 1, 255); // Update edge image
              Threshold_Ip.putPixel(
                  i, j + 1,
                  255); // Update threshold image (This is the output image from thresholding with
                        // hysteresis)
            }
            if (n8
                >= TLow) // If n8 is greater than or equal to the low threshold then we mark it as
                         // an edge
            {
              Copy_Edge_Ip.putPixel(i - 1, j + 1, 255); // Update edge image
              Threshold_Ip.putPixel(
                  i - 1, j + 1,
                  255); // Update threshold image (This is the output image from thresholding with
                        // hysteresis)
            }
          }
        }
      }
      count++; // Update counter and continue iterations
    }

    // Display the threshold with hysteresis image.
    String ThreshTitle = "Threshold with Hysteresis";
    ImagePlus Threshold_Im = new ImagePlus(ThreshTitle, Threshold_Ip);
    Threshold_Im.show();
    /**
     * ----------------------------------------------------- END STEP 4: THRESHOLDING WITH
     * HYSTERESIS -----------------------------------------------------*
     */

    /**
     * ------------------------------------------------------------------ END CANNY EDGE DETECTION
     * ------------------------------------------------------------------*
     */
  }