From 5a422aba704c375a307a902bafe658342e209906 Mon Sep 17 00:00:00 2001
From: scuri <scuri>
Date: Fri, 17 Oct 2008 06:10:15 +0000
Subject: First commit - moving from LuaForge to SourceForge

---
 src/process/im_canny.cpp | 254 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 254 insertions(+)
 create mode 100644 src/process/im_canny.cpp

(limited to 'src/process/im_canny.cpp')

diff --git a/src/process/im_canny.cpp b/src/process/im_canny.cpp
new file mode 100644
index 0000000..d749fc0
--- /dev/null
+++ b/src/process/im_canny.cpp
@@ -0,0 +1,254 @@
+/** \file
+ * \brief Canny Edge Detector
+ *
+ * See Copyright Notice in im_lib.h
+ * $Id: im_canny.cpp,v 1.1 2008/10/17 06:16:33 scuri Exp $
+ */
+
+#include <im.h>
+
+#include "im_process_loc.h"
+
+#include <math.h>
+#include <stdlib.h>
+#include <memory.h>
+
+/* Scale floating point magnitudes to 8 bits */
+static float MAG_SCALE;
+
+/* Biggest possible filter mask */
+#define MAX_MASK_SIZE 100
+
+static float ** f2d (int nr, int nc);
+static float gauss(float x, float sigma);
+static float dGauss (float x, float sigma);
+static float meanGauss (float x, float sigma);
+static void seperable_convolution (const imImage* im, float *gau, int width, float **smx, float **smy);
+static void dxy_seperable_convolution (float** im, int nr, int nc, float *gau, int width, float **sm, int which);
+static void nonmax_suppress (float **dx, float **dy, imImage* mag);
+
+void imProcessCanny(const imImage* im, imImage* NewImage, float stddev)
+{
+  int width = 1;
+  float **smx,**smy;
+  float **dx,**dy;
+  int i;
+  float gau[MAX_MASK_SIZE], dgau[MAX_MASK_SIZE];
+
+/* Create a Gaussian and a derivative of Gaussian filter mask */
+  for(i=0; i<MAX_MASK_SIZE; i++)
+  {
+    gau[i] = meanGauss ((float)i, stddev);
+    if (gau[i] < 0.005)
+    {
+      width = i;
+      break;
+    }
+    dgau[i] = dGauss ((float)i, stddev);
+  }
+
+  smx = f2d (im->height, im->width);
+  smy = f2d (im->height, im->width);
+
+/* Convolution of source image with a Gaussian in X and Y directions  */
+  seperable_convolution (im, gau, width, smx, smy);
+
+  MAG_SCALE = 0;
+
+/* Now convolve smoothed data with a derivative */
+  dx = f2d (im->height, im->width);
+  dxy_seperable_convolution (smx, im->height, im->width, dgau, width, dx, 1);
+  free(smx[0]); free(smx);
+
+  dy = f2d (im->height, im->width);
+  dxy_seperable_convolution (smy, im->height, im->width, dgau, width, dy, 0);
+  free(smy[0]); free(smy);
+
+  if (MAG_SCALE)
+    MAG_SCALE = 255.0f/(1.4142f*MAG_SCALE);
+
+  /* Non-maximum suppression - edge pixels should be a local max */
+  nonmax_suppress (dx, dy, NewImage);
+
+  free(dx[0]); free(dx);
+  free(dy[0]); free(dy);
+}
+
+static float norm (float x, float y)
+{
+  return (float) sqrt ( (double)(x*x + y*y) );
+}
+
+static float ** f2d (int nr, int nc)
+{
+  float **x, *y;
+  int i;
+
+  x = (float **)calloc ( nr, sizeof (float *) );
+  if (!x)
+    return NULL;
+
+  y = (float *)calloc ( nr*nc, sizeof (float) );
+  if (!y)
+    return NULL;
+
+  for (i=0; i<nr; i++)
+  {  
+    x[i] = y + i*nc;
+  }
+
+  return x;
+}
+
+/*      Gaussian        */
+static float gauss(float x, float sigma)
+{
+  return (float)exp((double) ((-x*x)/(2*sigma*sigma)));
+}
+
+static float meanGauss (float x, float sigma)
+{
+  float z;
+  z = (gauss(x,sigma)+gauss(x+0.5f,sigma)+gauss(x-0.5f,sigma))/3.0f;
+//  z = z/(3.1415f*2.0f*sigma*sigma);
+  return z;
+}
+
+/*      First derivative of Gaussian    */
+static float dGauss (float x, float sigma)
+{
+//  return -x/(sigma*sigma) * gauss(x, sigma);
+  return -x * gauss(x, sigma);
+}
+
+static void seperable_convolution (const imImage* im, float *gau, int width, float **smx, float **smy)
+{
+  int i,j,k, I1, I2, nr, nc;
+  float x, y;
+  unsigned char* im_data = (unsigned char*)im->data[0];
+
+  nr = im->height;
+  nc = im->width;
+
+  for (i=0; i<nr; i++)
+  {
+    for (j=0; j<nc; j++)
+    {
+      x = gau[0] * im_data[i*im->width + j]; y = gau[0] * im_data[i*im->width + j];
+      for (k=1; k<width; k++)
+      {
+        I1 = (i+k)%nr; I2 = (i-k+nr)%nr;
+        y += gau[k]*im_data[I1*im->width + j] + gau[k]*im_data[I2*im->width + j];
+        I1 = (j+k)%nc; I2 = (j-k+nc)%nc;
+        x += gau[k]*im_data[i*im->width + I1] + gau[k]*im_data[i*im->width + I2];
+      }
+      smx[i][j] = x; smy[i][j] = y;
+    }
+  }
+}
+
+static void dxy_seperable_convolution (float** im, int nr, int nc,  float *gau, int width, float **sm, int which)
+{
+  int i,j,k, I1, I2;
+  float x;
+
+  for (i=0; i<nr; i++)
+  {
+    for (j=0; j<nc; j++)
+    {
+      x = 0.0;
+      for (k=1; k<width; k++)
+      {
+        if (which == 0)
+        {
+          I1 = (i+k)%nr; I2 = (i-k+nr)%nr;
+          x += -gau[k]*im[I1][j] + gau[k]*im[I2][j];
+        }
+        else
+        {
+          I1 = (j+k)%nc; I2 = (j-k+nc)%nc;
+          x += -gau[k]*im[i][I1] + gau[k]*im[i][I2];
+        }
+      }
+      sm[i][j] = x;
+
+      if (x > MAG_SCALE)
+        MAG_SCALE = x;
+    }
+  }
+}
+
+static unsigned char tobyte(float x)
+{
+  if (x > 255) return 255;
+  return (unsigned char)x;
+}
+
+static void nonmax_suppress (float **dx, float **dy, imImage* mag)
+{
+  int i,j;
+  float xx, yy, g2, g1, g3, g4, g, xc, yc;
+  unsigned char* mag_data = (unsigned char*)mag->data[0];
+
+  for (i=1; i<mag->height-1; i++)
+  {
+    for (j=1; j<mag->width-1; j++)
+    {
+      /* Treat the x and y derivatives as components of a vector */
+      xc = dx[i][j];
+      yc = dy[i][j];
+      if (fabs(xc)<0.01 && fabs(yc)<0.01) continue;
+
+      g  = norm (xc, yc);
+
+      /* Follow the gradient direction, as indicated by the direction of
+        the vector (xc, yc); retain pixels that are a local maximum. */
+
+      if (fabs(yc) > fabs(xc))
+      {
+        /* The Y component is biggest, so gradient direction is basically UP/DOWN */
+        xx = (float)(fabs(xc)/fabs(yc));
+        yy = 1.0;
+
+        g2 = norm (dx[i-1][j], dy[i-1][j]);
+        g4 = norm (dx[i+1][j], dy[i+1][j]);
+        if (xc*yc > 0.0)
+        {
+          g3 = norm (dx[i+1][j+1], dy[i+1][j+1]);
+          g1 = norm (dx[i-1][j-1], dy[i-1][j-1]);
+        } 
+        else
+        {
+          g3 = norm (dx[i+1][j-1], dy[i+1][j-1]);
+          g1 = norm (dx[i-1][j+1], dy[i-1][j+1]);
+        }
+
+      } 
+      else
+      {
+        /* The X component is biggest, so gradient direction is basically LEFT/RIGHT */
+        xx = (float)(fabs(yc)/fabs(xc));
+        yy = 1.0;
+
+        g2 = norm (dx[i][j+1], dy[i][j+1]);
+        g4 = norm (dx[i][j-1], dy[i][j-1]);
+        if (xc*yc > 0.0)
+        {
+          g3 = norm (dx[i-1][j-1], dy[i-1][j-1]);
+          g1 = norm (dx[i+1][j+1], dy[i+1][j+1]);
+        }
+        else
+        {
+          g1 = norm (dx[i-1][j+1], dy[i-1][j+1]);
+          g3 = norm (dx[i+1][j-1], dy[i+1][j-1]);
+        }
+      }
+
+      /* Compute the interpolated value of the gradient magnitude */
+      if ( (g > (xx*g1 + (yy-xx)*g2)) && (g > (xx*g3 + (yy-xx)*g4)) )
+      {
+        mag_data[i*mag->width + j] = tobyte(g*MAG_SCALE);
+      } 
+    }
+  }
+}
-- 
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