- objective: create a simple edge detection program using sobel edge detection.
- chess picture images
- download sobel.c
- run sobel.c using "face05.pgm"
- add code to make sobel.c use thresholds (Hi threshold, Lo threshold)
- add three lines of code to generate header for .pgm viewer
- run program to get three outputs;
- magnitude image
- output due to hi threshold
- output due to low threshold
- run on chess image (garb34.pgm) and get three output images which should approximately match output from www.cs.ucf.edu/courses/cap4453/outputpics
- magnitude image (sobelmag.pgm)
- output due to hi threshold (sobelout1.pgm)
- output due to low threshold (sobelout2.pgm)
- header info: details image file type (P5), image size (width/height, 256 each), max intensity value (255).
- body: 2D array holding the integer (stored as char) pixel values representing intensity (or color) for each row/col in image
- 0 value for intesity: black
- 255 value for intensity: white
- everything inbetween is a tone of gray
- each pixel value is a single 1-byte integer stored as a char
- command-line args
- argc: number of args passed
- argv[]: pointer array pointing to each arg passed to program (argv[0] == name of program itself)
$ ./program.out argv[1] argv[2] .... argv[argc] // argv[0] == 'program.out' - compiling C program
# compile with gcc gcc program_name.c -o program_name # execute ./program_name argv[1] argv[2]
- command-line arg for running program:
# sobel.c with single threshold
./sobel input_img.pgm output_img.pgm threshold
# sobel.c with low/high threshold
./sobel input_img.pgm output_img.pgm low_threshold high_threshold
# sobel.c with three outputs + low/high threshold
./sobel input_img.pgm mag_out.pgm low_out.pgm hi_out.pgm low_threshold high_threshold
# output for face05.pgm
./sobel face05.pgm sobelmag.pgm sobelout1.pgm sobelout2.pgm 40 110
# output for garb34.pgm
./sobel garb34.pgm sobel_out.pgm sobel_low.pgm sobel_hi.pgm 40 110