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  1. /* sobel operatorで輝度のみ */
  2.  
  3. #include <stdlib.h>
  4. #include <math.h>
  5.  
  6. char *sobel_mask(char *src, int width, int height, int pitch)
  7. {
  8.     const int sobel_h[] = {1, 0, -1, 2, 0, -2, 1, 0, -1};
  9.     const int sobel_v[] = {1, 2, 1, 0, 0, 0, -1, -2, -1};
  10.  
  11.     char *dst = calloc(width * height, 1);
  12.     if (!dst) {
  13.         return NULL;
  14.     }
  15.  
  16.     char *srcp = src;
  17.     char *dstp = dst;
  18.     /* 画像端の処理は省略 */
  19.     for (int y = 1; y < width - 1; y++) {
  20.         char *top = srcp;
  21.         srcp += pitch;
  22.         char *bottom = srcp + pitch;
  23.         dstp += width;
  24.         for (int x = 1; x < width -1; x++) {
  25.             char array[] = {
  26.                 top[x - 1], top[x], top[x + 1],
  27.                 srcp[x - 1], srcp[x], srcp[x + 1],
  28.                 bottom[x - 1], bottom[x], bottom[x + 1]
  29.             }
  30.             int val_h = 0;
  31.             int val_v = 0;
  32.             for (int i = 0; i < 9; i++) {
  33.                 val_h += array[i] * sobel_h[i];
  34.                 val_v += array[i] * sobel_v[i];
  35.             }
  36.             dstp[x] = (char)(sqrt((double)(val_h * val_h + val_v * val_v)) / 8);
  37.         }
  38.     }
  39.  
  40.     return dst;
  41. }
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin 
Standard input is empty
compilation info 
prog.c: In function ‘sobel_mask’:
prog.c:30: error: expected ‘,’ or ‘;’ before ‘int’
prog.c:33: error: ‘val_h’ undeclared (first use in this function)
prog.c:33: error: (Each undeclared identifier is reported only once
prog.c:33: error: for each function it appears in.)
stdout 
Standard output is empty
https://ideone.com/PsP2Y
language:
C99 (gcc 8.3)
created:
12 years ago
visibility:
public

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