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