--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Meerwald-dir/wm_cox_e.c	Fri Dec 20 13:08:59 2024 +0100
@@ -0,0 +1,165 @@
+#include "wm.h"
+#include "dct.h"
+#include "netpbm/pgm.h"
+#include "sort.h"
+
+char *progname;
+
+void usage(void) {
+  fprintf(stderr, "usage: %s [-a n] [-h] [-o file] -s file file\n\n", progname);
+  fprintf(stderr, "\t-a n\t\talpha factor/embedding strength\n");
+  fprintf(stderr, "\t-h\t\tprint usage\n");
+  fprintf(stderr, "\t-o file\t\toutput (watermarked) file\n");
+  fprintf(stderr, "\t-s file\t\tsignature to embed in input image\n");
+  exit(0);
+}
+
+int main(int argc, char *argv[]) {
+
+  FILE *in = stdin;
+  FILE *out = stdout;
+  FILE *sig = NULL;
+
+  char output_name[MAXPATHLEN] = "(stdout)";
+  char input_name[MAXPATHLEN] = "(stdin)";
+  char signature_name[MAXPATHLEN];
+
+  int c;
+  int row;
+  int i,j;
+
+  int n;
+
+  double alpha = 0.0;
+  double threshold;
+
+  double *largest;
+  gray **input_image;
+  gray **output_image;
+  double **dcts;
+
+  gray maxval;
+  int rows, cols, format;
+
+  progname = argv[0];
+
+  pgm_init(&argc, argv); wm_init();
+
+  while ((c = getopt(argc, argv, "a:h?o:s:")) != EOF) {
+    switch (c) {
+      case 'a':
+        alpha = atof(optarg);
+        if (alpha <= 0.0) {
+          fprintf(stderr, "%s: alpha factor %f out of range\n", progname, alpha);
+          exit(1);
+        }
+        break;
+      case 'h':
+      case '?':
+        usage();
+        break;
+      case 'o':
+        if ((out = fopen(optarg, "wb")) == NULL) {
+          fprintf(stderr, "%s: unable to open output file %s\n", progname, optarg);
+          exit(1);
+        }
+        strcpy(output_name, optarg);
+        break;
+      case 's':
+        if ((sig = fopen(optarg, "r")) == NULL) {
+          fprintf(stderr, "%s: unable to open signature file %s\n", progname, optarg);
+          exit(1);
+        }
+        strcpy(signature_name, optarg);
+        break;
+    }
+  }
+
+  argc -= optind;
+  argv += optind;
+
+  if (argc > 1) {
+    usage();
+    exit(1);
+  }
+
+  if (argc == 1 && *argv[0] != '-') {
+    if ((in = fopen(argv[0], "rb")) == NULL) {
+      fprintf(stderr, "%s: unable to open input file %s\n", progname, argv[0]);
+      exit(1);
+    }
+    else
+      strcpy(input_name, argv[0]);
+  }
+  
+  if (sig) {
+    char line[32];
+    fgets(line, sizeof(line), sig);
+    if (strspn(line, "CXSG") >= 4) {
+      fscanf(sig, "%d\n", &n);
+      if (alpha == 0.0)
+        fscanf(sig, "%lf\n", &alpha);
+      else
+        fscanf(sig, "%*f\n");
+      fscanf(sig, "%*f\n");
+      fscanf(sig, "%*f\n");
+    }
+    else {
+      fprintf(stderr, "%s: invalid signature file %s\n", progname, signature_name);
+      exit(1);
+    }
+  }
+  else {
+    fprintf(stderr, "%s: signature file not specified, use -s file option\n", progname);
+    exit(1);
+  }
+
+  pgm_readpgminit(in, &cols, &rows, &maxval, &format);
+
+  init_dct_NxN(cols, rows);
+
+  dcts = alloc_coeffs(cols, rows);
+  input_image = pgm_allocarray(cols, rows);
+
+  for (row = 0; row < rows; row++)
+    pgm_readpgmrow(in, input_image[row], cols, maxval, format);
+
+  fclose(in);
+
+  output_image = pgm_allocarray(cols, rows);
+
+  fdct_NxN(input_image, dcts);
+
+  largest = malloc((n + 1) * sizeof(double));
+  select_largest_coeffs(dcts[0], cols * rows, n+1, largest);
+  threshold = largest[0];
+  free(largest);
+
+  j = 0;
+  for (i = 0; i < n; i++) {
+    double v;
+
+    while (dcts[j / cols][j % cols] < threshold) j++;
+
+    fscanf(sig, "%lf\n", &v);
+    dcts[j / cols][j % cols] *= (1.0 + alpha * v);
+    j++;
+  }
+
+  idct_NxN(dcts, output_image);
+  free_coeffs(dcts);
+
+  pgm_writepgminit(out, cols, rows, maxval, 0);
+
+  for (row = 0; row < rows; row++)
+    pgm_writepgmrow(out, output_image[row], cols, maxval, 0);
+
+  fclose(out);
+
+  fclose(sig);
+
+  pgm_freearray(output_image, rows);
+  pgm_freearray(input_image, rows);
+
+  exit(0);
+}