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=== Assignment #2 ===
== Subversion ==
[http://homepages.inf.ed.ac.uk/rbf/HIPR2/sobel.htm Description of Sobel's Algorithm] - This is a great website teachs us how it works, and it also provide some examples, which help us to implement in C code.
You can checkout the source for our projects using the subversion repository below.  Use your ISU NetID as both your username and password:
svn co http://svn.chaddington.com/cpre584


Compiler:
== Updating the UserApp for Sobel ==
 
[[Team Gryffindor - Sobel Source Code]]
gcc -O -lm sobel.c -o sobel
 
./sobel
 
Sobel edge detection algorithm code with C (''Since the code is very long, I just show key part of algorithm''):
 
  int sobel(double threshold) {
  unsigned int  x, y, i, v, u;            // for loop counter
  unsigned char R, G, B;        // color of R, G, B
  double val[MASK_N] = {0.0};
  int adjustX, adjustY, xBound, yBound;
  double total;
  for(y = 0; y != height; ++y) {
    for(x = 0; x != width; ++x) {
      for(i = 0; i != MASK_N; ++i) {
        adjustX = (MASK_X % 2) ? 1 : 0;
                adjustY = (MASK_Y % 2) ? 1 : 0;
                xBound = MASK_X / 2;
                yBound = MASK_Y / 2;
           
        val[i] = 0.0;
        for(v = -yBound; v != yBound + adjustY; ++v) {
                    for (u = -xBound; u != xBound + adjustX; ++u) {
            if (x + u >= 0 && x + u < width && y + v >= 0 && y + v < height) {
              R = *(image_s + byte_per_pixel * (width * (y+v) + (x+u)) + 2);
              G = *(image_s + byte_per_pixel * (width * (y+v) + (x+u)) + 1);
              B = *(image_s + byte_per_pixel * (width * (y+v) + (x+u)) + 0);
             
                  val[i] +=    color_to_int(R, G, B) * mask[i][u + xBound][v + yBound];
            }
                    }
        }
      }
      total = 0.0;
      for (i = 0; i != MASK_N; ++i) {
              total += val[i] * val[i];
      }
          total = sqrt(total);
         
      if (total - threshold >= 0) {
        // black
        *(image_t + byte_per_pixel * (width * y + x) + 2) = BLACK;
        *(image_t + byte_per_pixel * (width * y + x) + 1) = BLACK;
        *(image_t + byte_per_pixel * (width * y + x) + 0) = BLACK;
      }
            else {
              // white
        *(image_t + byte_per_pixel * (width * y + x) + 2) = WHITE;
        *(image_t + byte_per_pixel * (width * y + x) + 1) = WHITE;
        *(image_t + byte_per_pixel * (width * y + x) + 0) = WHITE;
      }
    }
  }
 
  return 0;
}
 
We use color lena with 24bit bmp file
[[Image:lena.jpg|200px|thumb|left|alt text]]
 
[[Image:Lena_sobel.jpg|200px|thumb|left|alt text]]
 
== Profiling Sobel edge detection algorithm  ==
 
This command will generate a test file:
gcc -lm -pg sobel.c
./a.out
gprof a.out > test
 
test file:
 
%      cumulative  self            self    total         
   
'''80.80'''      0.15    0.15        1  145.44  175.53  sobel
16.72      0.18    0.03  4706312    0.00    0.00  color_to_int
0.00      0.18    0.00        1    0.00    0.00  read_bmp
0.00      0.18    0.00        1    0.00    0.00  write_bmp
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
=== Assignment #2 (New Algorithm)===
Compiler:
 
gcc -O -lm sobel.c -o sobel
 
./sobel
 
Sobel edge detection algorithm code with C
 
void sobel_filtering( )
    /* Spatial filtering of image data */
    /* Sobel filter (horizontal differentiation */
    /* Input: image1[y][x] ---- Outout: image2[y][x] */
{
  /* Definition of Sobel filter in horizontal direction */
  int maskx[3][3] = {{-1,0,1},{-2,0,2},{-1,0,1}};
  int masky[3][3] = {{1,2,1},{0,0,0},{-1,-2,-1}};
  double pixel_value_x, pixel_value_y, pixel_value;
  double min, max;
  int x, y, i, j;  /* Loop variable */
  /* Initialization of image2[y][x] */
  x_size2 = x_size1;
  y_size2 = y_size1;
  for (y = 0; y < y_size2; y++) {
    for (x = 0; x < x_size2; x++) {
      image2[y][x] = 0;
    }
  }
  /* Generation of image2 after linear transformtion */
  for (y = 1; y < y_size1 - 1; y++) {
    for (x = 1; x < x_size1 - 1; x++) {
      pixel_value_x = 0.0;
      pixel_value_y = 0.0;
      for (j = -1; j <= 1; j++) {
    for (i = -1; i <= 1; i++) {
              pixel_value_x += image1[y+j][x+i] * maskx[j+1][i+1];// do x-convolution
              pixel_value_y += image1[y+j][x+i] * masky[j+1][i+1];// do y-convolution
    }     
      pixel_value = (abs(pixel_value_x)+abs(pixel_value_y)); // easier to implement on hardware 
      if (pixel_value >= 255)pixel_value=255;
      if (pixel_value <= 0)pixel_value=0;   
      image2[y][x] = (unsigned char)pixel_value;
    }
  }
}
}
main( )
{
  load_image_data( );  /* Input of image1 */
  sobel_filtering( );  /* Sobel filter is applied to image1 */
  save_image_data( );  /* Output of image2 */
  return 0;
}

Latest revision as of 17:45, 27 February 2012

Team Gryffindor
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Gryffindor Team Logo
Team Members
Chad Nelson - cnel711
Mihir Awatramani - mihir
Mengduo Ma - marinama
Kuan-Hsing Ho - pm429015

Subversion

You can checkout the source for our projects using the subversion repository below. Use your ISU NetID as both your username and password:

svn co http://svn.chaddington.com/cpre584

Updating the UserApp for Sobel

Team Gryffindor - Sobel Source Code