|
|
| (6 intermediate revisions by 3 users not shown) |
| Line 9: |
Line 9: |
| }} | | }} |
|
| |
|
| === 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
| |
| | |
| * files
| |
| ** mypgm.h - header file
| |
| ** sobel.c - sobel algorithm
| |
| ** Lena.pgm - image files
| |
| | |
| 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;
| |
| }
| |
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
