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4 <TITLE>Scaler servlet</TITLE>
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7 <H1>Scaler</H1>
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9 <p>A Servlet for scaling images. (Version 1.9b)</p>
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10
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11 <h2>Web API</h2>
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12
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13 <p>The Scaler servlet takes parameters in the http request format:
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14 <code>Scaler/request_path/?param1=value1¶m2=value2&...</code>
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15 Unknown parameters will be silently ignored.</p>
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16
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17 <p>Recognised parameters:
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18 <ul>
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19 <li><b>request_path</b> path to file or directory.</li>
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20
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21 <li><b>fn</b> path to file or directory below <code>/docuserver/images</code>
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22 (or other configured image directory).
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23 This path will be added to the <code>request_path</code> behind the servlet name.
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24 Either parameter can be empty.</li>
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25
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26 <li><b>pn</b> page number. Index into the (alphabetically sorted) directory
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27 given by the path. Starts with 1. Ignored if the path points to a file.
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28 Default: 1.</li>
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29
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30 <li><b>dw</b> destination image width (pixels).</li>
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31
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32 <li><b>dh</b> destination image height (pixels).</li>
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33
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34 <li><b>wx</b> relative x offset of the image area to be sent (0 <= wx <= 1).
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35 Default: 0.</li>
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36
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37 <li><b>wy</b> relative y offset of the image area to be sent (0 <= wy <= 1).
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38 Default: 0.</li>
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39
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40 <li><b>ww</b> relative width of the image area to be sent (0 <= ww <= 1).
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41 Default: 1.</li>
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42
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43 <li><b>wh</b> relative height of the image area to be sent (0 <= wh <= 1).
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44 Default: 1.</li>
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45
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46 <li><b>ws</b> additional scaling factor. The resulting image will have the size
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47 <code>[ws*dw,ws*dh]</code>. Default: 1.</li>
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48
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49 <li><b>mo</b> flags for the mode of operation separated by ",".
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50 <ul>
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51 <li><b>fit</b>: always scale the image to fit
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52 <code>[dw,dh]</code>.<br>
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53 <b>file</b>: send the file as-is (may
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54 be very large and all sorts of image types!). If configuration
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55 doesn't allow sending files
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56 (<code>sendfile-allowed=false</code>) revert to
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57 <code>clip</code>.<br>
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58 <b>clip</b>: send the file in its
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59 original resolution, cropped to fit <code>[dw,dh]</code>.<br> If
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60 none of these flags is set heuristics is used (send unzoomed GIF
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61 as-is).<br>
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62 <b>osize</b>: scale to original size based on the image resolution
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63 (from the image metadata) and display resolution (from parameter
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64 <code>ddpi</code>)
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65 </li>
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67 <li><b>errtxt</b>: send error response as HTML.<br>
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68 <b>errimg</b>: response as image (default).</li>
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70 <li><b>q0</b>-<b>q2</b>: quality of interpolation in scaling
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71 (<code>q0</code>: worst, default).</li>
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72
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73 <li><b>lores</b>: try to use scaled image (default)<br>
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74 <b>hires</b>: always use unscaled image.<br>
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75 If the image is zoomed (ww, wh < 1) the unscaled image is
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76 used in any case.</li>
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77
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78 <li><b>vmir</b>: mirror image vertically.<br>
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79 <b>hmir</b>: mirror image horizontally.</li>
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80 </ul>
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81 </li>
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83 <li><b>cont</b>: change contrast of the image. Negative value
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84 reduces contrast, positive value enhances contrast. Pixel value is
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85 multiplied by 2^cont. Default: 0</li>
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87 <li><b>brgt</b>: change brightness of image. Negative value reduces
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88 brightness, positive value enhances brightness. The value brgt is
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89 added to the pixel value. Default: 0</li>
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90
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91 <li><b>rot</b>: rotate image. Rotation angle is given in
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92 degrees. Default: 0</li>
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93
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94 <li><b>rgbm</b>: modify color by multiplication. The contrast of the
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95 red green and blue components of the image can be reduced or
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96 enhanced similar to the <code>cont</code> parameter. The factors for
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97 red, green and blue are separated by slashes (for example
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98 0.86/0/-0.5). Default: 0/0/0</li>
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99
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100 <li><b>rgba</b>: modify color by addition. The brightness of the red
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101 green and blue components of the image can be reduced or enhanced
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102 similar to the <code>brgt</code> parameter. The factors for red,
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103 green and blue are separated by slashes (for example
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104 100/0/25). Default: 0/0/0</li>
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105
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106 <li><b>ddpi</b>: resolution of client display for <code>osize</code> mode.
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107 Either <code>ddpi</code> or <code>ddpix</code> and <code>ddpiy</code> must
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108 be set to use <code>osize</code> mode.</li>
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109
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110 <li><b>ddpix</b>: resolution of client display in x direction for
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111 <code>osize</code> mode.</li>
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114 <li><b>ddpiy</b>: resolution of client display in y direction for
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115 <code>osize</code> mode.</li>
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116
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117 </ul>
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118 The image will be scaled equally in horizontal and vertical direction such that
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119 the resulting image does not exceed the rectangle <code>[ww,wh]</code>.
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120 </p>
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122 </BODY>
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123 </HTML>
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