--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Meerwald-dir/wm_koch_e.c	Fri Dec 20 13:08:59 2024 +0100
@@ -0,0 +1,354 @@
+#include "wm.h"
+#include "dct.h"
+#include "signature.h"
+#include "coord.h"
+#include "gray.h"
+#include "netpbm/pgm.h"
+
+char *progname;
+
+double sign(double x) {
+    if (x >= 0.0) return 1.0;
+    else return -1.0;
+}
+
+double try_modif(gray **image_block, double **dcts, int c1, int c2, double w1, double w2) {
+    int i, j;
+    gray **altered_block;
+    double **altered_dcts;
+    double sum;
+
+    altered_block = alloc_grays_8x8();
+    altered_dcts = alloc_coeffs_8x8();
+
+    for (i = 0; i < 8; i++) {
+        memcpy(altered_dcts[i], dcts[i], sizeof(double) * 8);
+    }
+        
+    // put the changed coefficients back to black
+    altered_dcts[c1 / NJPEG][c1 % NJPEG] = w1;
+    altered_dcts[c2 / NJPEG][c2 % NJPEG] = w2;
+
+    dequantize_8x8(altered_dcts);
+
+    idct_block_8x8(altered_dcts, altered_block, 0, 0);
+    
+    // compute MSE
+    sum = 0.0;
+    for (i = 0; i < 8; i++) {
+        for (j = 0; j < 8; j++) {  
+            double ib = image_block[i][j];
+            double ab = altered_block[i][j];
+            sum += (ib - ab) * (ib - ab);
+        }
+    }
+    sum /= 64.0;
+    
+    free(altered_block);
+    free(altered_dcts);
+    
+    return sum;
+}
+
+void usage(void) {
+  fprintf(stderr, "usage: %s [-h] [-l n] [-o file] [-q n] [-v n] -s file file\n", progname);
+  fprintf(stderr, "\t-h\t\tprint usage\n");
+  fprintf(stderr, "\t-l n\t\tsignature robustness factor\n");
+  fprintf(stderr, "\t-o file\t\toutput (watermarked) file\n");
+  fprintf(stderr, "\t-q n\t\tquantization (JPEG quality) factor\n");
+  fprintf(stderr, "\t-s file\t\tsignature to embed in input image\n");
+  fprintf(stderr, "\t-v n\t\tverbosity level\n");
+  exit(0);
+}
+
+int main(int argc, char *argv[]) {
+
+  FILE *in = stdin;
+  FILE *out = stdout;
+  FILE *sig = NULL;
+
+  char signature_name[MAXPATHLEN];
+  char input_name[MAXPATHLEN] = "(stdin)";
+  char output_name[MAXPATHLEN] = "(stdout)";
+
+  int c;
+  int n;
+
+  int seed;
+  int verbose = 0;
+
+  int rows, cols, format;
+  gray maxval;
+  int row;
+
+  int quantization = 0;
+  double quality = 0.0;
+
+  struct coords *coords;
+
+  gray **image;
+  double **dcts;
+  gray **image_block;
+
+  progname = argv[0]; 
+
+  pgm_init(&argc, argv); wm_init();
+
+  while ((c = getopt(argc, argv, "h?i:l:o:q:s:v:")) != EOF) {
+    switch (c) {
+      case 'h':
+      case '?':
+        usage();
+        break;
+      case 'l':
+        quality = atof(optarg);
+        if (quality <= 0.0) {
+          fprintf(stderr, "%s: signature strength factor %f out of range\n", progname, quality);
+          exit(1);
+        }
+        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 'q':
+        quantization = atoi(optarg);
+        if (quantization <= 0 || quantization > 100) {
+          fprintf(stderr, "%s: quantization factor %d out of range\n", progname, quantization);
+          exit(1);
+        }
+        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;
+      case 'v':
+        verbose = atoi(optarg);
+        if (verbose < 0) {
+          fprintf(stderr, "%s: verbosity level %d out of range\n", progname, verbose);
+          exit(1);
+        }
+        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[128];
+    fgets(line, sizeof(line), sig);
+    if (strspn(line, "KCSG") >= 4) {
+      fscanf(sig, "%d\n", &nbit_signature);
+      if (quality == 0.0)
+        fscanf(sig, "%lf\n", &quality);
+      else
+        fscanf(sig, "%*f\n");
+      if (quantization == 0)
+        fscanf(sig, "%d\n", &quantization);
+      else
+        fscanf(sig, "%*d\n");
+      fscanf(sig, "%d\n", &seed);
+      n_signature = NBITSTOBYTES(nbit_signature);
+      fread(signature, sizeof(char), n_signature, sig);
+      fscanf(sig, "\n");
+      srandom(seed);
+    }
+    else {
+      fprintf(stderr, "%s: invalid signature file %s\n", progname, signature_name);
+      exit(1);
+    }
+    fclose(sig);
+  }
+  else {
+    fprintf(stderr, "%s: signature file not specified, use -s file option\n", progname);
+    exit(1);
+  }
+
+  pgm_readpgminit(in, &cols, &rows, &maxval, &format);
+
+  if (cols % NJPEG) {
+    fprintf(stderr, "%s: image width %d not a multiple of %d\n", progname, cols, NJPEG);
+    exit(1);
+  }
+
+  if (rows % NJPEG) {
+    fprintf(stderr, "%s: image height %d not a multiple of %d\n", progname, rows, NJPEG);
+    exit(1);
+  }
+
+  if ((cols * rows) / (NJPEG * NJPEG) < nbit_signature) {
+    fprintf(stderr, "%s: image not large enough to embed %d bits of signature\n", progname, nbit_signature);
+    exit(1);
+  }
+
+  init_dct_8x8();
+  init_quantum_JPEG_lumin(quantization);
+
+  dcts = alloc_coeffs_8x8();
+  image_block = alloc_grays_8x8();
+
+  if ((coords = alloc_coords(nbit_signature)) == NULL) {
+    fprintf(stderr, "%s: unable to allocate memory\n", progname);
+    exit(1);
+  }
+
+  image = pgm_allocarray(cols, rows);
+
+  for (row = 0; row < rows; row++)
+    pgm_readpgmrow(in, image[row], cols, maxval, format);
+
+  fclose(in);
+
+  // embedding signature bits by modifying two coefficient relationship,
+  // one bit for each block
+  n = 0;
+  while (n < nbit_signature) {
+    int xb;
+    int yb;
+    int c1, c2;
+    double v1, v2;
+    double w1, w2;
+    double best_w1, best_w2;
+    double diff;
+    double mod;
+    double try;
+    double best_mse;
+    int no_mse_opt = 0;
+
+    // randomly select a block, check to get distinct blocks
+    // (don't watermark a block twice)
+    do {
+      xb = random() % (cols / NJPEG);
+      yb = random() % (rows / NJPEG);
+    } while (add_coord(coords, xb, yb) < 0);
+
+    // do the forward 8x8 DCT of that block
+    fdct_block_8x8(image, xb * NJPEG, yb * NJPEG, dcts);
+
+    copy_grays_to_block(image_block, image, xb*NJPEG, yb*NJPEG, NJPEG, NJPEG);
+
+    // randomly select two distinct coefficients from block
+    // only accept coefficients in the middle frequency range
+    do {
+      c1 = (random() % (NJPEG * NJPEG - 2)) + 1;
+      c2 = (random() % (NJPEG * NJPEG - 2)) + 1;
+    } while (c1 == c2 || !is_middle_frequency_coeff_8x8(c1) || !is_middle_frequency_coeff_8x8(c2));
+
+    // quantize block according to quantization quality parameter
+    quantize_8x8(dcts);
+
+    if (verbose > 0)
+      fprintf(stderr, "%d: quantized DCT block (x %d/y %d), modifying (x %d/y %d), (x %d/y %d) for %s\n", n, xb * NJPEG, yb * NJPEG, c1 % NJPEG, c1 / NJPEG, c2 % NJPEG, c2 / NJPEG, get_signature_bit(n) ? "HIGH" : "LOW");
+    if (verbose > 5)
+      print_coeffs_8x8(dcts);
+
+    v1 = dcts[c1 / NJPEG][c1 % NJPEG];
+    v2 = dcts[c2 / NJPEG][c2 % NJPEG];
+
+    best_w1 = DBL_MAX, best_w2 = DBL_MAX;
+    try = 0.0;
+    best_mse = DBL_MAX;
+
+    diff = fabs(v1) - fabs(v2);
+
+    if (get_signature_bit(n)) 
+      mod = fabs(quality - ( fabs(v1) - fabs(v2) ));
+    else
+      mod = fabs(quality -  (fabs(v2) - fabs(v1)));
+    
+    if (verbose > 2)
+        fprintf(stderr, "%d / %d: %.2f %.2f %.2f | %d\n", xb, yb, diff, v1, v2, get_signature_bit(n));    
+    
+    while (try <= mod) {
+        w1 = v1;
+        w2 = v2;
+
+        // modify coefficient's relationship to embed signature bit
+        // using mean square error to minimize error
+        if (get_signature_bit(n)) {
+          if (diff < quality) {
+            // we have to impose the relationship, does not occur naturally
+            w1 = sign(v1)*(fabs(v1) + mod - try);
+            w2 = sign(v2)*(fabs(v2) - try);
+          }
+        }
+        else {
+          if (diff > -quality) {
+            // force the relationship
+            w2 = sign(v2)*(fabs(v2) + mod - try);
+            w1 = sign(v1)*(fabs(v1) - try);
+          }
+        }
+
+        double mse = try_modif(image_block, dcts, c1, c2, w1, w2);
+        if (mse < best_mse) {
+            best_w1 = w1;
+            best_w2 = w2;
+            best_mse = mse;
+        }
+        
+        if (verbose > 2)
+            fprintf(stderr, "%d / %d: MSE %.2f %.2f; %.2f: %.2f %.2f\n", xb, yb, mse, best_mse, try, w1, w2);
+        
+        if (fabs(mse) == 1e-3)
+            break;
+        
+        if (fabs(fabs(w1) - fabs(w2) + quality) > 1e-3)
+            break;
+
+        if (no_mse_opt)
+            break;
+
+        try += 0.05;
+    }
+
+    if (verbose > 1)
+      fprintf(stderr, "  %f -> %f, %f -> %f\n", v1, best_w1, v2, best_w2);
+
+    // put the changed coefficients back to black
+    dcts[c1 / NJPEG][c1 % NJPEG] = best_w1;
+    dcts[c2 / NJPEG][c2 % NJPEG] = best_w2;
+
+    // the obvious :-)
+    dequantize_8x8(dcts);
+
+    // do the inverse DCT on the modified 8x8 block
+    idct_block_8x8(dcts, image, xb * NJPEG, yb * NJPEG);
+
+    n++;
+  }
+
+  free_grays(image_block);
+  free_coeffs(dcts);
+
+  pgm_writepgminit(out, cols, rows, maxval, 0);
+  for (row = 0; row < rows; row++)
+    pgm_writepgmrow(out, image[row], cols, maxval, 0);
+
+  fclose(out);
+
+  pgm_freearray(image, rows);
+
+  exit(0);
+}