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1 ## Copyright (C) 2012 Pantxo Diribarne |
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2 ## |
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3 ## This program is free software; you can redistribute it and/or modify |
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4 ## it under the terms of the GNU General Public License as published by |
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5 ## the Free Software Foundation; either version 3 of the License, or |
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6 ## (at your option) any later version. |
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7 ## |
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8 ## This program is distributed in the hope that it will be useful, |
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9 ## but WITHOUT ANY WARRANTY; without even the implied warranty of |
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10 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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11 ## GNU General Public License for more details. |
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12 ## |
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13 ## You should have received a copy of the GNU General Public License |
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14 ## along with Octave; see the file COPYING. If not, see |
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15 ## <http://www.gnu.org/licenses/>. |
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16 |
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17 ## -*- texinfo -*- |
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18 ## @deftypefn {Function File} {@var{B} =} imtransform (@var{A}, @var{T}) |
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19 ## @deftypefnx {Function File} {@var{B} =} imtransform (@var{A}, @var{T}, @var{interp}) |
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20 ## @deftypefnx {Function File} {@var{B} =} imtransform (@dots{}, @var{prop}, @var{val}) |
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21 ## Transform image. |
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22 ## |
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23 ## Given an image @var{A} in one space, returns an image @var{B} |
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24 ## resulting from the forward transform defined in the transformation |
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25 ## structure @var{T}. An additionnal input argument @var{interp}, |
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26 ## 'bicubic', 'bilinear' (default) or 'nearest', |
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27 ## specifies the interpolation method to be used. Finally, the |
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28 ## transformation can be tuned using @var{prop}/@var{val} pairs. The |
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29 ## following properties are supported: |
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30 ## |
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31 ## @table @asis |
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32 ## @item "udata" |
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33 ## Specifies the input space horizontal limits. Value must be a two |
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34 ## elements vector [minval maxval]. Default: [1 columns(@var{A})] |
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35 ## |
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36 ## @item "vdata" |
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37 ## Specifies the input space vertical limits. Value must be a two |
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38 ## elements vector [minval maxval]. Default: [1 rows(@var{A})] |
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39 ## |
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40 ## @item "xdata" |
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41 ## Specifies the requiered output space horizontal limits. Value must |
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42 ## be a two elements vector [minval maxval]. Default: estimated using |
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43 ## udata, vdata and findbounds function. |
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44 ## |
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45 ## @item "ydata" |
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46 ## Specifies the requiered output space vertical limits. Value must |
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47 ## be a two elements vector [minval maxval]. Default: estimated using |
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48 ## udata, vdata and findbounds function. |
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49 ## |
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50 ## @item "xyscale" |
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51 ## Specifies the output scale in outputspace_units/pixel. If a scalar |
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52 ## is provided, both vertical and horizontal dimensions are scaled the |
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53 ## same way. If @var{val} is a two element vector, it must indicate |
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54 ## consecutively horizontal and vertical scales. Default value is |
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55 ## computed using the input space scale provided |
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56 ## that the number of pixel of any dimension of the output image does |
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57 ## not exceed 20000. |
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58 ## |
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59 ## @item "size" |
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60 ## Size of the output image (1-by-2 vector). Overrides the effect of |
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61 ## "xyscale" property. |
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62 ## |
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63 ## @item "fillvalues" |
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64 ## Color of the areas where no interpolation where possible, e.g. when |
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65 ## coorfinates of points in the output space are out of the limits of |
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66 ## the input space. @var{val} must be coherent with the input image |
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67 ## format: for grayscale and indexed images (2D) @var{val} must be |
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68 ## scalar, for RGB (n-by-m-by-3) @var{val} must be a 3 element vector. |
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69 ## e.g.: |
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70 ## |
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71 ## @end table |
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72 ## |
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73 ## @seealso{maketform, cp2tform, tforminv, tformfwd, findbounds} |
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74 ## @end deftypefn |
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75 |
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76 ## Author: Pantxo Diribarne <pantxo@dibona> |
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77 |
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78 function [varargout] = imtransform (im, T, varargin) |
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79 |
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80 if (nargin < 2) |
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81 print_usage (); |
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82 elseif (! istform (T)) |
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83 error ("imtransform: T must be a transformation structure (see `maketform')"); |
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84 endif |
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85 |
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86 ## Parameters |
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87 interp = "linear"; |
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88 imdepth = size (im, 3); |
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89 maximsize = [20000 20000]; |
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90 |
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91 udata = [1; columns(im)]; |
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92 vdata = [1; rows(im)]; |
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93 xdata = ydata = []; |
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94 xyscale = []; |
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95 imsize = []; |
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96 fillvalues = ones (1, imdepth) * NaN; |
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97 |
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98 if (isempty (varargin)) |
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99 xydata = findbounds (T, [udata vdata]); |
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100 xdata = xydata(:,1); |
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101 ydata = xydata(:,2); |
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102 else |
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103 ## interp |
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104 if (floor (numel (varargin)/2) != numel (varargin)/2) |
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105 allowed = {"bicubic", "bilinear", "nearest"}; |
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106 tst = strcmp (varargin{1}, allowed); |
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107 if (!any (tst)) |
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108 error ("imtransform: expect one of %s as interp method", disp (allowed)); |
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109 else |
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110 interp = {"pchip", "linear", "nearest"}{find (tst)}; |
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111 endif |
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112 varargin = varargin(2:end); |
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113 endif |
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114 |
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115 ## options |
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116 allowed = {"udata", "vdata", "xdata", "ydata", ... |
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117 "xyscale", "size", "fillvalues"}; |
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118 props = varargin(1:2:end); |
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119 vals = varargin(2:2:end); |
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120 np = numel (props); |
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121 if (!all (cellfun (@ischar, props))) |
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122 error ("imtransform: expect property/value pairs."); |
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123 endif |
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124 |
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125 props = tolower (props); |
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126 tst = cellfun (@(x) any (strcmp (x, allowed)), props); |
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127 if (!all (tst)) |
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128 error ("imtransform: unknown property %s", disp (props{!tst})); |
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129 endif |
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130 |
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131 ## u(vxy)data |
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132 iolims = allowed(1:4); |
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133 for ii = 1:numel (iolims) |
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134 tst = cellfun (@(x) any (strcmp (x, iolims{ii})), props); |
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135 if (any (tst)) |
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136 prop = props{find (tst)(1)}; |
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137 val = vals{find (tst)(1)}; |
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138 if (isnumeric (val) && numel (val) == 2) |
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139 if (isrow (val)) |
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140 val = val'; |
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141 endif |
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142 eval (sprintf ("%s = val;", prop), |
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143 "error (\"imtransform: %s\n\", lasterr ());"); |
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144 else |
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145 error ("imtransform: expect 2 elements real vector for %s", prop) |
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146 endif |
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147 endif |
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148 endfor |
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149 if (isempty (xdata) && isempty (ydata)) |
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150 xydata = findbounds (T, [udata vdata]); |
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151 xdata = xydata(:,1); |
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152 ydata = xydata(:,2); |
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153 elseif (isempty (xdata)) |
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154 xydata = findbounds (T, [udata vdata]); |
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155 xdata = xydata(:,1); |
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156 elseif (isempty (ydata)) |
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157 xydata = findbounds (T, [udata vdata]); |
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158 ydata = xydata(:,2); |
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159 endif |
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160 |
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161 ## size and xyscale |
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162 tst = strcmp ("size", props); |
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163 if (any (tst)) |
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164 val = vals{find (tst)(1)}; |
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165 if (isnumeric (val) && numel (val) == 2 && |
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166 all (val > 0)) |
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167 imsize = val; |
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168 else |
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169 error ("imtransform: expect 2 elements real vector for size"); |
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170 endif |
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171 elseif (any (tst = strcmp ("xyscale", props))) |
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172 val = vals{find (tst)(1)}; |
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173 if (isnumeric (val) && all (val > 0)) |
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174 if (numel (val) == 1) |
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175 xyscale(1:2) = val; |
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176 elseif (numel (val) == 2) |
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177 xyscale = val; |
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178 else |
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179 error ("imtransform: expect 1 or 2 element(s) real vector for xyscale"); |
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180 endif |
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181 else |
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182 error ("imtransform: expect 1 or 2 elements real vector for xyscale"); |
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183 endif |
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184 else |
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185 xyscale = [(diff (udata) / columns (im)) (diff (vdata) / rows (im))]; |
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186 endif |
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187 |
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188 ## Fillvalues |
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189 tst = strcmp ("fillvalues", props); |
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190 if (any (tst)) |
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191 val = vals{find (tst)(1)}; |
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192 if (isnumeric (val) && numel (val) == 1) |
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193 fillvalues(1:end) = val; |
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194 elseif (isnumeric (val) && numel (val) == 3) |
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195 fillvalues = val; |
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196 else |
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197 error ("imtransform: expect 1 or 3 elements real vector for `fillvalues'"); |
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198 endif |
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199 endif |
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200 endif |
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201 |
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202 ## Ouput/Input pixels |
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203 if (isempty (imsize)) |
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204 if (isempty (xyscale)) |
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205 xyscale = [(diff (udata) / columns (im)) (diff (vdata) / rows (im))]; |
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206 endif |
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207 xscale = xyscale(1); |
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208 yscale = xyscale(2); |
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209 xsize = floor (diff (xdata) / xscale); |
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210 ysize = floor (diff (ydata) / yscale); |
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211 if (xsize > maximsize(2) || ysize > maximsize(1)) |
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212 if (xsize >= ysize) |
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213 scalefactor = (diff (xdata) / maximsize(2)) / xscale; |
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214 else |
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215 scalefactor = (diff (ydata) / maximsize(1)) / yscale; |
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216 endif |
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217 xscale *= scalefactor |
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218 yscale *= scalefactor |
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219 xsize = floor (diff (xdata) / xscale); |
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220 ysize = floor (diff (ydata) / yscale); |
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221 warning ("imtransform: output image two large, adjusting the largest dimension to %d", maximsize); |
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222 endif |
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223 imsize = [ysize xsize]; |
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224 endif |
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225 [xx yy] = meshgrid (linspace (xdata(1), xdata(2), imsize(2)), |
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226 linspace (ydata(1), ydata(2), imsize(1))); |
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227 |
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228 [uu vv] = meshgrid (linspace (udata(1), udata(2), size(im)(2)), |
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229 linspace (vdata(1), vdata(2), size(im)(1))); |
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230 |
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231 ## Input coordinates |
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232 [uui, vvi] = tforminv (T, reshape (xx, numel (xx), 1), |
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233 reshape (yy, numel (yy), 1)); |
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234 uui = reshape (uui, size (xx)); |
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235 vvi = reshape (vvi, size (yy)); |
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236 ## Interpolation |
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237 for layer = 1:imdepth |
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238 imout(:,:,layer) = interp2 (uu, vv, im(:,:,layer), ... |
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239 uui, vvi, interp, fillvalues(layer)); |
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240 endfor |
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241 if (nargout == 1) |
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242 varargout{1} = imout; |
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243 else |
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244 varargout = {imout, xdata, ydata}; |
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245 endif |
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246 endfunction |
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247 |
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248 %!demo |
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249 %! ## Various linear transforms |
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250 %! figure (); |
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251 %! im = [checkerboard(20, 2, 4); checkerboard(40, 1, 2)]; |
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252 %! %input space corners |
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253 %! incp = [1 1; 160 1; 160 160; 1 160]; |
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254 %! udata = [min(incp(:,1)) max(incp(:,1))]; |
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255 %! vdata = [min(incp(:,2)) max(incp(:,2))]; |
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256 %! subplot (2,3,1); |
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257 %! imshow (im) |
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258 %! hold on |
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259 %! plot (incp(:,1), incp(:,2), 'ob') |
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260 %! axis on |
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261 %! xlabel ('Original') |
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262 %! |
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263 %! % Translation and scaling |
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264 %! outcp = incp * 2; |
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265 %! outcp(:,1) += 200; |
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266 %! outcp(:,2) += 500; |
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267 %! T = maketform ('affine', incp(1:3,:), outcp(1:3,:)); |
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268 %! subplot (2,3,2); |
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269 %! [im2 xdata ydata] = imtransform (im, T, 'udata', udata, |
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270 %! 'vdata', vdata, 'fillvalues', 1); |
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271 %! imh = imshow (im2); set (imh, 'xdata', xdata, 'ydata', ydata) |
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272 %! set (gca, 'xlim', xdata, 'ylim', ydata) |
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273 %! axis on, hold on, xlabel ('Translation / Scaling'); |
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274 %! plot (outcp(:,1), outcp(:,2), 'or') |
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275 %! |
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276 %! % Shear |
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277 %! outcp = [1 1; 160 1; 140 160; -19 160]; % affine only needs 3 control points |
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278 %! T = maketform ('affine', incp(1:3,:), outcp(1:3,:)); |
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279 %! subplot (2,3,3); |
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280 %! [im2 xdata ydata] = imtransform (im, T, 'udata', udata, |
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281 %! 'vdata', vdata, 'fillvalues', 1); |
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282 %! imh = imshow (im2); set (imh, 'xdata', xdata, 'ydata', ydata) |
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283 %! set (gca, 'xlim', xdata, 'ylim', ydata) |
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284 %! axis on, hold on, xlabel ('Shear'); |
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285 %! plot (outcp(:,1), outcp(:,2), 'or') |
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286 %! |
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287 %! % Rotation |
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288 %! theta = pi/4; |
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289 %! T = maketform ('affine', [cos(theta) -sin(theta); ... |
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290 %! sin(theta) cos(theta); 0 0]); |
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291 %! outcp = tformfwd (T, incp); |
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292 %! subplot (2,3,4); |
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293 %! [im2 xdata ydata] = imtransform (im, T, 'udata', udata, |
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294 %! 'vdata', vdata, 'fillvalues', 1 ); |
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295 %! imh = imshow (im2); set (imh, 'xdata', xdata, 'ydata', ydata) |
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296 %! set (gca, 'xlim', xdata, 'ylim', ydata) |
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297 %! axis on, hold on, xlabel ('Rotation'); |
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298 %! plot (outcp(:,1), outcp(:,2), 'or') |
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299 %! |
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300 %! % Reflection around x axis |
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301 %! outcp = incp; |
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302 %! outcp(:,2) *= -1; |
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303 %! T = cp2tform (incp, outcp, 'similarity'); |
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304 %! subplot (2,3,5); |
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305 %! [im2 xdata ydata] = imtransform (im, T, 'udata', udata, |
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306 %! 'vdata', vdata, 'fillvalues', 1 ); |
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307 %! imh = imshow (im2); set (imh, 'xdata', xdata, 'ydata', ydata) |
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308 %! set (gca, 'xlim', xdata, 'ylim', ydata) |
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309 %! axis on, hold on, xlabel ('Reflection'); |
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310 %! plot (outcp(:,1), outcp(:,2), 'or') |
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311 %! |
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312 %! % Projection |
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313 %! outcp = [1 1; 160 -40; 220 220; 12 140]; |
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314 %! T = maketform ('projective', incp, outcp); |
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315 %! subplot (2,3,6); |
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316 %! [im2 xdata ydata] = imtransform (im, T, 'udata', udata, |
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317 %! 'vdata', vdata, 'fillvalues', 1 ); |
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318 %! imh = imshow (im2); set (imh, 'xdata', xdata, 'ydata', ydata) |
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319 %! set (gca, 'xlim', xdata, 'ylim', ydata) |
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320 %! axis on, hold on, xlabel ('Projection'); |
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321 %! plot (outcp(:,1), outcp(:,2), 'or') |
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322 |
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323 %!demo |
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324 %! ## Streched image |
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325 %! rad = 2; % minimum value: 4/pi |
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326 %! [uu vv] = meshgrid ((-2:2)/rad, (-2:2)/rad); |
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327 %! rescfactor = sin ((uu.^2 + vv.^2).^.5); |
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328 %! inpts = [(reshape (uu, numel (uu), 1)), (reshape (vv, numel (uu), 1))]; |
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329 %! xx = rescfactor .* sign(uu); |
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330 %! yy = rescfactor .* sign(vv); |
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331 %! outpts = [reshape(xx, numel (xx), 1) reshape(yy, numel (yy), 1)]; |
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332 %! |
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333 %! T = cp2tform (inpts, outpts, "polynomial", 4); |
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334 %! figure; |
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335 %! subplot (1,2,1) |
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336 %! im = zeros (800, 800, 3); |
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337 %! im(:,:,1) = checkerboard (100) > 0.2; |
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338 %! im(:,:,3) = checkerboard (100) < 0.2; |
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339 %! [im2 xdata ydata] = imtransform (im, T, 'udata', [-2 2], |
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340 %! 'vdata', [-2 2], 'fillvalues', |
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341 %! [0 1 0]); |
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342 %! imh = imshow (im2); |
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343 %! set (imh, 'xdata', xdata, 'ydata', ydata) |
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344 %! set (gca, 'xlim', xdata, 'ylim', ydata) |
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345 %! [im cmap] = imread ('default.img'); |
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346 %! subplot (1,2,2) |
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347 %! [im2 xdata ydata] = imtransform (im, T, 'udata', [-1 1], |
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348 %! 'vdata', [-1 1], 'fillvalues', |
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349 %! round (length (cmap) / 2)); |
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350 %! imh = imshow (im2, cmap); |
