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1 #include "wm.h"
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2 #include "kim_common.h"
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3
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4
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5 // find the largest absolute coefficient of a subband
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6 double find_subband_largest_coeff(Image_tree s, int subband, int verbose) {
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7 int i, j;
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8 double max;
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9
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10 max = 0.0;
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11 for (i = 5; i < s->image->height-5; i++)
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12 for (j = 5; j < s->image->width-5; j++) {
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13 double coeff;
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14
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15 coeff = fabs(get_pixel(s->image, i, j));
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16 if (coeff > max)
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17 max = coeff;
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18 }
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19
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20 if (verbose > 8)
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21 fprintf(stderr, " subband %f\n", max);
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22
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23 return max;
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24 }
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25
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26 // find largest absolute coefficient of the detail subbands (LH, HL, HH) of
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27 // a decomposition level
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28 double find_level_largest_coeff(Image_tree p, int verbose) {
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29 double h, v, d;
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30
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31 h = find_subband_largest_coeff(p->horizontal, HORIZONTAL, verbose);
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32 v = find_subband_largest_coeff(p->vertical, VERTICAL, verbose);
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33 d = find_subband_largest_coeff(p->diagonal, DIAGONAL, verbose);
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34
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35 return MAX(h, MAX(v, d));
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36 }
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37
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38 // calculate the significance threshold given the maximum absolute
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39 // coefficient at a decomposition level
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40 double calc_level_threshold(double max_coeff, int verbose) {
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41 double threshold;
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42
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43 threshold = pow(2.0, floor(log(max_coeff) / log(2.0)) - 1.0);
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44
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45 if (verbose > 7)
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46 fprintf(stderr, " max %f, threshold %f\n", max_coeff, threshold);
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47
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48 return threshold;
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49 }
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50
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51 // calculate an appropriate embedding strength for a given decomposition level
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52 // and a base alpha strength
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53 double calc_level_alpha_detail(double alpha, int maxlevels, int level, int verbose) {
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54 double level_alpha;
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55
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56 level_alpha = alpha / pow(2.0, level - 1);
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57
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58 return level_alpha;
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59 }
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60
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