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<h1>Scaler</h1>

<p>A Servlet for scaling images. (Version 1.5.2)</p>

<h2>Web API</h2>

<p>The Scaler servlet takes parameters in the http request format:
<code>Scaler/request_path/?param1=value1&amp;param2=value2&amp;...</code>
Unknown parameters will be silently ignored.</p>

<p>Recognised parameters:</p>
<ul>
  <li><b>request_path</b> path to file or directory.</li>

  <li><b>fn</b> path to file or directory below <code>/docuserver/images</code>
    (or other configured image directory).
    This path will be added to the <code>request_path</code> behind the servlet name.
    Either parameter can be empty.</li>

  <li><b>pn</b> page number. Index into the (alphabetically sorted) directory
    given by the path. Starts with 1. Ignored if the path points to a file.
    Default: 1.</li>

  <li><b>dw</b> destination image width (pixels). If omitted the image is scaled to fit
    dh.</li>

  <li><b>dh</b> destination image height (pixels). If omitted the image is scaled to fit
    dw.</li>

  <li><b>wx</b> relative x offset of the image area to be sent (0 &lt;= wx &lt;= 1).
    Default: 0.</li>

  <li><b>wy</b> relative y offset of the image area to be sent (0 &lt;= wy &lt;= 1).
    Default: 0.</li>

  <li><b>ww</b> relative width of the image area to be sent (0 &lt;= ww &lt;= 1).
    Default: 1.</li>

  <li><b>wh</b> relative height of the image area to be sent (0 &lt;= wh &lt;= 1).
    Default: 1.</li>

  <li><b>ws</b> additional scaling factor. The resulting image will have the size
    <code>[ws*dw,ws*dh]</code>. Default: 1.</li>

    <li><b>mo</b> flags for the mode of operation separated by ",".
    <ul>
      <li><b>fit</b>: always scale the image to fit
      <code>[dw,dh]</code> (default).<br>

      <b>clip</b>: send the file in its
      original resolution, cropped to fit <code>[dw,dh]</code>.
      <br>

      <b>osize</b>: scale to original size based on the image resolution
      (from the image metadata) and display resolution (from parameter
      <code>ddpi</code>). Fails if either resolution is unknown.
      </li>

      <li>
      <b>file</b>: send the file as-is (may
      be very large and all sorts of image types!). If configuration
      doesn't allow sending files
      (<code>sendfile-allowed=false</code>) revert to
      <code>clip</code>.<br>

      <b>rawfile</b>: send the file as-is with a mime-type of
      <code>application/octet-stream</code> so it can be downloaded with
      the browser.
      </li>

      <li><b>errtxt</b>: send error response as HTML.<br>
      <b>errimg</b>: response as image (default).</li>

      <li><b>q0</b>-<b>q2</b>: quality of interpolation in scaling
      (<code>q0</code>: worst, default).</li>

      <li><b>lores</b>: try to use scaled image (default)<br>

      <b>hires</b>: always use unscaled image.<br>

      If the image is zoomed (ww, wh &lt; 1) the use of the scaled
      image files depends on the requested resolution.</li>

      <li><b>vmir</b>: mirror image vertically.<br>

      <b>hmir</b>: mirror image horizontally.</li>

      <li><b>jpg</b>: the resulting image is always sent as JPEG
      (otherwise TIFF and PNG images are sent as PNG).
      </li>
    </ul>
  </li>

  <li><b>cont</b>: change contrast of the image. Negative value
  reduces contrast, positive value enhances contrast. Pixel value is
  multiplied by 2^cont. Default: 0</li>

  <li><b>brgt</b>: change brightness of image. Negative value reduces
  brightness, positive value enhances brightness. The value brgt is
  added to the pixel value. Default: 0</li>

  <li><b>rot</b>: rotate image. Rotation angle is given in
  degrees. Default: 0</li>

  <li><b>rgbm</b>: modify color by multiplication. The contrast of the
  red green and blue components of the image can be reduced or
  enhanced similar to the <code>cont</code> parameter. The factors for
  red, green and blue are separated by slashes (for example
  0.86/0/-0.5). Default: 0/0/0</li>

  <li><b>rgba</b>: modify color by addition. The brightness of the red
  green and blue components of the image can be reduced or enhanced
  similar to the <code>brgt</code> parameter. The factors for red,
  green and blue are separated by slashes (for example
  100/0/25). Default: 0/0/0</li>

  <li><b>ddpi</b>: resolution of client display for <code>osize</code> mode.
  Either <code>ddpi</code> or <code>ddpix</code> and <code>ddpiy</code> must
  be set to use <code>osize</code> mode.</li>

  <li><b>ddpix</b>: resolution of client display in x direction for
  <code>osize</code> mode.</li>

  <li><b>ddpiy</b>: resolution of client display in y direction for
  <code>osize</code> mode.</li>

</ul>

  <p>The image to be loaded can be specified by the
  <code>request_path</code> (deprecated) or the <code>fn</code>
   (preferred) parameter and the optional index <code>pn</code></p>
  <ul>
      <li> if <code>fn</code> points to a directory then the file with
      the index <code>pn</code> (in alphabetical order according to
      ASCII) will be loaded</li>

      <li>if <code>fn</code> points to a file (with or without
      extension) then this file will be loaded</li>
  </ul>

  <p>The image will be scaled equally in horizontal and vertical
  direction such that the resulting image does not exceed the rectangle
  <code>[dw,dh]</code>. If only either height or width is given the
  image is scaled to match only the given parameter. The size of the
  resulting image in the other parameter is determined by the aspect
  ratio of the image.
  </p>

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author	robcast
date	Fri, 09 Nov 2012 19:48:04 +0100
parents	7779b37d1d05
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