1 | /* file: localmax.c |
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2 | ** author: Andrea Vedaldi |
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3 | ** description: Find local maximizer of multi-dimensional array. |
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4 | **/ |
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5 | |
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6 | /* AUTORIGHTS |
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7 | Copyright (C) 2006 Andrea Vedaldi |
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8 | |
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9 | This file is part of VLUtil. |
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10 | |
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11 | VLUtil is free software; you can redistribute it and/or modify |
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12 | it under the terms of the GNU General Public License as published by |
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13 | the Free Software Foundation; either version 2, or (at your option) |
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14 | any later version. |
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15 | |
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16 | This program is distributed in the hope that it will be useful, |
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17 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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18 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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19 | GNU General Public License for more details. |
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20 | |
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21 | You should have received a copy of the GNU General Public License |
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22 | along with this program; if not, write to the Free Software Foundation, |
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23 | Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
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24 | */ |
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25 | |
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26 | #include"mex.h" |
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27 | #include<mexutils.c> |
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28 | #include<stdlib.h> |
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29 | |
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30 | /** Matlab driver. |
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31 | **/ |
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32 | #define greater(a,b) ((a) > (b)+threshold) |
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33 | |
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34 | void |
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35 | mexFunction(int nout, mxArray *out[], |
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36 | int nin, const mxArray *in[]) |
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37 | { |
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38 | int M, N ; |
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39 | const double* F_pt ; |
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40 | int ndims ; |
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41 | int pdims = -1 ; |
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42 | int* offsets ; |
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43 | int* midx ; |
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44 | int* neighbors ; |
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45 | int nneighbors ; |
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46 | int* dims ; |
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47 | enum {F=0,THRESHOLD,P} ; |
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48 | enum {MAXIMA=0} ; |
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49 | double threshold = - mxGetInf() ; |
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50 | |
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51 | /* ------------------------------------------------------------------ |
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52 | * Check the arguments |
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53 | * --------------------------------------------------------------- */ |
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54 | if (nin < 1) { |
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55 | mexErrMsgTxt("At least one input argument is required."); |
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56 | } else if (nin > 3) { |
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57 | mexErrMsgTxt("At most three arguments are allowed.") ; |
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58 | } else if (nout > 1) { |
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59 | mexErrMsgTxt("Too many output arguments"); |
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60 | } |
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61 | |
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62 | /* The input must be a real matrix. */ |
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63 | if (!mxIsDouble(in[F]) || mxIsComplex(in[F])) { |
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64 | mexErrMsgTxt("Input must be real matrix."); |
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65 | } |
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66 | |
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67 | if(nin > 1) { |
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68 | if(!uIsRealScalar(in[THRESHOLD])) { |
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69 | mexErrMsgTxt("THRESHOLD must be a real scalar.") ; |
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70 | } |
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71 | threshold = *mxGetPr(in[THRESHOLD]) ; |
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72 | } |
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73 | |
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74 | if(nin > 2) { |
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75 | if(!uIsRealScalar(in[P])) |
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76 | mexErrMsgTxt("P must be a non-negative integer") ; |
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77 | pdims = (int) *mxGetPr(in[P]) ; |
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78 | if(pdims < 0) |
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79 | mexErrMsgTxt("P must be a non-negative integer") ; |
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80 | } |
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81 | |
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82 | ndims = mxGetNumberOfDimensions(in[F]) ; |
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83 | { |
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84 | /* We need to make a copy because in one special case (see below) |
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85 | we need to adjust dims[]. |
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86 | */ |
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87 | int d ; |
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88 | dims = mxMalloc(sizeof(int)*ndims) ; |
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89 | const int* const_dims = mxGetDimensions(in[F]) ; |
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90 | for(d=0 ; d < ndims ; ++d) dims[d] = const_dims[d] ; |
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91 | } |
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92 | M = dims[0] ; |
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93 | N = dims[1] ; |
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94 | F_pt = mxGetPr(in[F]) ; |
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95 | |
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96 | /* |
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97 | If there are only two dimensions and if one is singleton, then |
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98 | assume that a vector has been provided as input (and treat this |
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99 | as a COLUMN matrix with p=1). We do this because Matlab does not |
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100 | distinguish between vectors and 1xN or Mx1 matrices and because |
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101 | the cases 1xN and Mx1 are trivial (the result is alway empty). |
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102 | */ |
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103 | if((ndims == 2) && (pdims < 0) && (M == 1 || N == 1)) { |
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104 | pdims = 1 ; |
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105 | M = (M>N)?M:N ; |
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106 | N = 1 ; |
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107 | dims[0]=M ; |
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108 | dims[1]=N ; |
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109 | } |
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110 | |
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111 | /* search the local maxima along the first p dimensions only */ |
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112 | if(pdims < 0) |
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113 | pdims = ndims ; |
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114 | |
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115 | if(pdims > ndims) { |
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116 | mxFree(dims) ; |
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117 | mexErrMsgTxt("P must not be greater than the number of dimensions") ; |
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118 | } |
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119 | |
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120 | /* ------------------------------------------------------------------ |
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121 | * Do the job |
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122 | * --------------------------------------------------------------- */ |
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123 | { |
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124 | int maxima_size = M*N ; |
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125 | int* maxima_start = mxMalloc(sizeof(int) * maxima_size) ; |
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126 | int* maxima_iterator = maxima_start ; |
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127 | int* maxima_end = maxima_start + maxima_size ; |
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128 | int i,h,o ; |
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129 | const double* pt = F_pt ; |
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130 | |
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131 | /* Compute the offsets between dimensions. */ |
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132 | offsets = mxMalloc(sizeof(int) * ndims) ; |
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133 | offsets[0] = 1 ; |
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134 | for(h = 1 ; h < ndims ; ++h) |
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135 | offsets[h] = offsets[h-1]*dims[h-1] ; |
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136 | |
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137 | /* Multi-index. */ |
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138 | midx = mxMalloc(sizeof(int) * ndims) ; |
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139 | for(h = 0 ; h < ndims ; ++h) |
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140 | midx[h] = 1 ; |
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141 | |
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142 | /* Neighbors. */ |
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143 | nneighbors = 1 ; |
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144 | o=0 ; |
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145 | for(h = 0 ; h < pdims ; ++h) { |
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146 | nneighbors *= 3 ; |
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147 | midx[h] = -1 ; |
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148 | o -= offsets[h] ; |
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149 | } |
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150 | nneighbors -= 1 ; |
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151 | neighbors = mxMalloc(sizeof(int) * nneighbors) ; |
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152 | i = 0 ; |
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153 | |
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154 | while(true) { |
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155 | if(o != 0 ) |
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156 | neighbors[i++] = o ; |
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157 | h = 0 ; |
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158 | while( o += offsets[h], (++midx[h]) > 1 ) { |
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159 | o -= 3*offsets[h] ; |
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160 | midx[h] = -1 ; |
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161 | if(++h >= pdims) |
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162 | goto stop ; |
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163 | } |
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164 | } |
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165 | stop: ; |
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166 | |
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167 | /* Starts at the corner (1,1,...,1,0,0,...0) */ |
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168 | for(h = 0 ; h < pdims ; ++h) { |
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169 | midx[h] = 1 ; |
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170 | pt += offsets[h] ; |
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171 | } |
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172 | for(h = pdims ; h < ndims ; ++h) { |
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173 | midx[h] = 0 ; |
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174 | } |
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175 | |
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176 | /* --------------------------------------------------------------- |
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177 | * Loop |
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178 | * ------------------------------------------------------------ */ |
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179 | |
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180 | /* |
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181 | If any dimension in the first P is less than 3 elements wide |
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182 | then just return the empty matrix (if we proceed without doing |
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183 | anything we break the carry reporting algorithm below). |
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184 | */ |
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185 | for(h=0 ; h < pdims ; ++h) |
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186 | if(dims[h] < 3) goto end ; |
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187 | |
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188 | while(true) { |
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189 | |
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190 | /* Propagate carry along multi index midx */ |
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191 | h = 0 ; |
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192 | while((midx[h]) >= dims[h] - 1) { |
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193 | pt += 2*offsets[h] ; /* skip first and last el. */ |
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194 | midx[h] = 1 ; |
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195 | if(++h >= pdims) |
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196 | goto next_layer ; |
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197 | ++midx[h] ; |
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198 | } |
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199 | |
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200 | /* |
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201 | for(h = 0 ; h < ndims ; ++h ) |
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202 | mexPrintf("%d ", midx[h]) ; |
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203 | mexPrintf(" -- %d -- pdims %d \n", pt - F_pt,pdims) ; |
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204 | */ |
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205 | |
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206 | /* Scan neighbors */ |
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207 | double v = *pt ; |
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208 | bool is_greater = (v >= threshold) ; |
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209 | i = 0 ; |
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210 | while(is_greater && i < nneighbors) |
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211 | is_greater &= v > *(pt + neighbors[i++]) ; |
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212 | |
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213 | /* Add the local maximum */ |
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214 | if(is_greater) { |
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215 | /* Need more space? */ |
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216 | if(maxima_iterator == maxima_end) { |
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217 | maxima_size += M*N ; |
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218 | maxima_start = mxRealloc(maxima_start, |
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219 | maxima_size*sizeof(int)) ; |
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220 | maxima_end = maxima_start + maxima_size ; |
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221 | maxima_iterator = maxima_end - M*N ; |
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222 | } |
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223 | |
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224 | *maxima_iterator++ = pt - F_pt + 1 ; |
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225 | } |
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226 | |
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227 | /* Go to next element */ |
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228 | pt += 1 ; |
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229 | ++midx[0] ; |
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230 | continue ; |
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231 | |
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232 | next_layer: ; |
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233 | if( h >= ndims ) |
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234 | goto end ; |
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235 | |
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236 | while((++midx[h]) >= dims[h]) { |
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237 | midx[h] = 0 ; |
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238 | if(++h >= ndims) |
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239 | goto end ; |
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240 | } |
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241 | } |
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242 | end:; |
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243 | /* Return. */ |
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244 | { |
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245 | double* M_pt ; |
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246 | out[MAXIMA] = mxCreateDoubleMatrix |
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247 | (1, maxima_iterator-maxima_start, mxREAL) ; |
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248 | maxima_end = maxima_iterator ; |
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249 | maxima_iterator = maxima_start ; |
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250 | M_pt = mxGetPr(out[MAXIMA]) ; |
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251 | while(maxima_iterator != maxima_end) { |
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252 | *M_pt++ = *maxima_iterator++ ; |
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253 | } |
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254 | } |
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255 | |
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256 | /* Release space. */ |
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257 | mxFree(offsets) ; |
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258 | mxFree(neighbors) ; |
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259 | mxFree(midx) ; |
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260 | mxFree(maxima_start) ; |
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261 | } |
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262 | mxFree(dims) ; |
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263 | } |
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