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1 @c Copyright (C) 1996, 1997 John W. Eaton |
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2 @c This is part of the Octave manual. |
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3 @c For copying conditions, see the file gpl.texi. |
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4 |
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5 @node Image Processing, Audio Processing, Signal Processing, Top |
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6 @chapter Image Processing |
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7 |
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8 Octave can display images with the X Window System using the |
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9 @code{xloadimage} program. You do not need to be running X in order to |
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10 manipulate images, however, so some of these functions may be useful |
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11 even if you are not able to view the results. |
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12 |
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13 Loading images only works with Octave's image format (a file with a |
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14 matrix containing the image data, and a matrix containing the |
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15 colormap). Contributions of robust, well-written functions to read |
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16 other image formats are welcome. If you can provide them, or would like |
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17 to improve Octave's image processing capabilities in other ways, please |
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18 contact @email{bug-octave@@bevo.che.wisc.edu}. |
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19 |
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20 @deftypefn {Function File} {} colormap (@var{map}) |
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21 @deftypefnx {Function File} {} colormap ("default") |
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22 Set the current colormap. |
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23 |
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24 @code{colormap (@var{map})} sets the current colormap to @var{map}. The |
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25 color map should be an @var{n} row by 3 column matrix. The columns |
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26 contain red, green, and blue intensities respectively. All entries |
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27 should be between 0 and 1 inclusive. The new colormap is returned. |
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28 |
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29 @code{colormap ("default")} restores the default colormap (a gray scale |
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30 colormap with 64 entries). The default colormap is returned. |
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31 |
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32 With no arguments, @code{colormap} returns the current color map. |
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33 @end deftypefn |
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34 |
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35 @deftypefn {Function File} {} gray (@var{n}) |
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36 Return a gray colormap with @var{n} entries corresponding to values from |
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37 0 to @var{n}-1. The argument @var{n} should be a scalar. If it is |
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38 omitted, 64 is assumed. |
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39 @end deftypefn |
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40 |
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41 @deftypefn {Function File} {[@var{img}, @var{map}] =} gray2ind (@var{}) |
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42 Convert a gray scale intensity image to an Octave indexed image. |
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43 @end deftypefn |
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44 |
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45 @deftypefn {Function File} {} image (@var{x}, @var{zoom}) |
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46 Display a matrix as a color image. The elements of @var{x} are indices |
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47 into the current colormap and should have values between 1 and the |
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48 length of the colormap. If @var{zoom} is omitted, a value of 4 is |
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49 assumed. |
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50 @end deftypefn |
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51 |
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52 @deftypefn {Function File} {} imagesc (@var{x}, @var{zoom}) |
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53 Display a scaled version of the matrix @var{x} as a color image. The |
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54 matrix is scaled so that its entries are indices into the current |
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55 colormap. The scaled matrix is returned. If @var{zoom} is omitted, a |
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56 value of 4 is assumed. |
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57 @end deftypefn |
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58 |
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59 @deftypefn {Function File} {} imshow (@var{x}, @var{map}) |
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60 @deftypefnx {Function File} {} imshow (@var{x}, @var{n}) |
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61 @deftypefnx {Function File} {} imshow (@var{i}, @var{n}) |
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62 @deftypefnx {Function File} {} imshow (@var{r}, @var{g}, @var{b}) |
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63 Display images. |
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64 |
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65 @code{imshow (@var{x})} displays an indexed image using the current |
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66 colormap. |
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67 |
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68 @code{imshow (@var{x}, @var{map})} displays an indexed image using the |
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69 specified colormap. |
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70 |
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71 @code{imshow (@var{i}, @var{n})} displays a gray scale intensity image. |
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72 |
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73 @code{imshow (@var{r}, @var{g}, @var{b})} displays an RGB image. |
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74 @end deftypefn |
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75 |
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76 @deftypefn {Function File} {} ind2gray (@var{x}, @var{map}) |
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77 Convert an Octave indexed image to a gray scale intensity image. |
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78 If @var{map} is omitted, the current colormap is used to determine the |
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79 intensities. |
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80 @end deftypefn |
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81 |
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82 @deftypefn {Function File} {[@var{r}, @var{g}, @var{b}] =} ind2rgb (@var{x}, @var{map}) |
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83 Convert an indexed image to red, green, and blue color components. |
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84 If @var{map} is omitted, the current colormap is used for the conversion. |
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85 @end deftypefn |
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86 |
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87 @deftypefn {Function File} {[@var{x}, @var{map}] =} loadimage (@var{file}) |
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88 Load an image file and it's associated color map from the specified |
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89 @var{file}. The image must be stored in Octave's image format. |
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90 @end deftypefn |
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91 |
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92 @deftypefn {Function File} {} rgb2ntsc (@var{rgb}) |
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93 Image format conversion. |
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94 @end deftypefn |
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95 |
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96 @deftypefn {Function File} {} ntsc2rgb (@var{yiq}) |
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97 Image format conversion. |
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98 @end deftypefn |
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99 |
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100 @deftypefn {Function File} {} ocean (@var{n}) |
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101 Create color colormap. The argument @var{n} should be a scalar. If it |
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102 is omitted, 64 is assumed. |
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103 @end deftypefn |
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104 |
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105 @deftypefn {Function File} {[@var{x}, @var{map}] =} rgb2ind (@var{r}, @var{g}, @var{b}) |
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106 Convert and RGB image to an Octave indexed image. |
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107 @end deftypefn |
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108 |
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109 @deftypefn {Function File} {} saveimage (@var{file}, @var{x}, @var{fmt}, @var{map}) |
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110 Save the matrix @var{x} to @var{file} in image format @var{fmt}. Valid |
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111 values for @var{fmt} are |
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112 |
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113 @table @code |
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114 @item "img" |
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115 Octave's image format. The current colormap is also saved in the file. |
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116 |
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117 @item "ppm" |
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118 Portable pixmap format. |
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119 |
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120 @item "ps" |
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121 PostScript format. Note that images saved in PostScript format can not |
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122 be read back into Octave with loadimage. |
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123 @end table |
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124 |
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125 If the fourth argument is supplied, the specified colormap will also be |
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126 saved along with the image. |
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127 |
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128 Note: if the colormap contains only two entries and these entries are |
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129 black and white, the bitmap ppm and PostScript formats are used. If the |
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130 image is a gray scale image (the entries within each row of the colormap |
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131 are equal) the gray scale ppm and PostScript image formats are used, |
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132 otherwise the full color formats are used. |
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133 @end deftypefn |
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134 |
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135 @defvr {Built-in Variable} IMAGEPATH |
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136 A colon separated list of directories in which to search for image |
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137 files. |
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138 @end defvr |
