doc/localhost/ALE/download/ale-0.5.1-user/rendering/index.html

   1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
   2 <html>
   3 <head>
   4   <title>ALE User Manual: Rendering</title>
   5
   6 <style type="text/css">
   7   TABLE.ba { max-width: 678; text-align: center; padding-bottom: 15; padding-top: 5}
   8   TABLE.inline { padding-right: 300; clear: left}
   9   TD.text_table {padding-left: 2; padding-right: 2; border-width: 1}
  10   H2 {clear: left}
  11   P {max-width: none; padding-right: 300; clear: left}
  12   BLOCKQUOTE {padding-right: 400 }
  13   LI {max-width: 640; clear: left}
  14   P.footer {max-width: none; width: auto; padding-left: 0}
  15   P.header {max-width: none; width: auto; padding-left: 0}
  16   HR.main {max-width: 640; clear: left; padding-left: 0; margin-left: 0}
  17   HR.footer {clear: both}
  18 </style>
  19 </head><body>
  20
  21
  22
  23 <table align=right valign=top width=160>
  24 <td valign=top height=600 width=160>
  25 <a href="http://auricle.dyndns.org/ALE/">
  26 <big>ALE</big>
  27 <br>
  28 Image Processing Software
  29 <br>
  30 <br>
  31 <small>Deblurring, Anti-aliasing, and Superresolution.</small></a>
  32 <br><br>
  33 <big>
  34 Local Operation
  35 </big>
  36 <hr>
  37 localhost<br>
  38 2684415918<br>
  39 </table>
  40
  41
  42
  43 <p><b>[ <a href="../">Up</a> ]</b></p>
  44 <h1>ALE Rendering</h1>
  45
  46 Rendering determines how an output image is constructed from a series of
  47 aligned input frames.  The incremental renderers, merging and drizzling, update
  48 the output image after reading each new frame from the series, whereas the
  49 non-incremental renderers wait until the last frame has been loaded to produce
  50 output.  More than one renderer can be involved in producing the final output image.
  51 Available rendering options are outlined below.
  52
  53 <h2>Merging</h2>
  54
  55 Merging, the default incremental renderer, works most effectively on images
  56 that have no large changes in scale (e.g. camera zooming).  Since it uses
  57 bilinear interpolation, output images are approximately convolved with the
  58 triangle, or Bartlett, filter, and may appear to have reduced contrast and
  59 resolution in comparison with other renderers.
  60
  61 <h2>Drizzling</h2>
  62
  63 The drizzling renderer is an incremental renderer that can usually produce
  64 better images than merging, but it works most effectively with devices having
  65 very little blur and optical distortion.  Devices sampling very small angles of
  66 the scene at each pixel are ideal; hence, if very fine staircase aliasing is
  67 visible in the input frames, drizzling should work very well.  (For creation of
  68 higher resolution images with drizzling, use also the --scale option described
  69 below.)
  70
  71 <pre>
  72 --drizzle-diam=x  Drizzle with input pixel diameter x (where 0 &lt; x &lt;= 1).
  73 --drizzle-only    If drizzling, output black for pixels with no drizzle data.
  74 </pre>
  75
  76 <p>For more information about drizzling, see the paper by Richard Hook and
  77 Andrew Fruchter, "Variable-Pixel Linear Combination", or the following URL:
  78
  79 <p><a href="http://www.cv.nrao.edu/adass/adassVI/hookr.html">http://www.cv.nrao.edu/adass/adassVI/hookr.html</a>
  80
  81 <h2>High-frequency enhancement</h2>
  82
  83 <p>This renderer uses an unsharp mask to enhance the contrast of high
  84 frequencies.  It can be used to compensate for systematic blurriness introduced
  85 by merging, drizzling, or the image capture device.  However, better results
  86 will generally be achievable by using a separate postprocessing tool, such as
  87 <a href="http://www.gimp.org">the GIMP</a> or <a
  88 href="http://cinepaint.sourceforge.net/">CinePaint</a> (formerly called Film
  89 GIMP).  In addition to the built-in unsharp mask, the GIMP can make use of
  90 Ernest Lippe's <a href="http://refocus.sourceforge.net/">refocus</a> plugin.
  91
  92 <pre>
  93 --hf-enhance=x    Enhance high frequency details by factor x.  (0.0 is default)
  94 </pre>
  95
  96 <h2>Irani-Peleg iterative image reconstruction</h2>
  97
  98 This renderer is by far the most general, and can be used to compensate for
  99 blurring introduced by the image capture device.  In order to use it most
 100 effectively, an approximation of the projection function for the capture device
 101 should be known.  Two general classes of projection functions are supported: box
 102 filters and custom filters.
 103
 104 <p>If rendering with the box filter option, manual experimentation can be used
 105 to find a diameter that works well.  Alternatively, ALE includes a script that
 106 calibrates custom filters for devices, based on images captured from known
 107 scenes.
 108
 109 <p>Two custom filter options are included: one for the IBM PC Camera Pro
 110 (XVP610) in 320x240 mode, and one for interactive filter specification.
 111
 112 <p>Note that this option can take a long time to produce output, especially on
 113 large images.  If incremental output is enabled (see below), output is written after
 114 each iteration is complete.  Using more iterations will generally improve
 115 output, up to the point of convergence, when additional iterations have no
 116 effect.  A dot is displayed to indicate the completion of each iteration.
 117
 118 <pre>
 119 --ip &lt;d> &lt;i>      Solve for a box filter with diameter &lt;d> over &lt;i> iterations.
 120 --ipc &lt;c> &lt;i>     Solve for device config &lt;c> over &lt;i> iterations.
 121 </pre>
 122
 123 The available device configurations are as follows:
 124
 125 <pre>
 126 xvp610_320x240
 127 stdin
 128 </pre>
 129
 130 <p>For more information on the backprojection technique of Michal Irani and Shmuel
 131 Peleg, see their paper, "Improving Resolution by Image Registration", at
 132
 133 <p><a href="ftp://ftp.wisdom.weizmann.ac.il/pub/irani/PAPERS/SR_CVGIP91.pdf">ftp://ftp.wisdom.weizmann.ac.il/pub/irani/PAPERS/SR_CVGIP91.pdf</a>
 134
 135 <h2>Scale factor</h2>
 136
 137 Rendering with a larger scale factor causes internal data structures to store
 138 more information, resulting in image output of the specified larger scale.
 139 Larger scales can improve alignment precision and output image quality, but can
 140 also increase alignment and rendering times.
 141
 142 <pre>
 143 --scale=x         Scale images by the factor x (where x is at least 1.0)
 144 </pre>
 145
 146 <h2>Image extents</h2>
 147
 148 The --extend option records pixel data that falls outside of the region of the
 149 first frame in the sequence.  This can be useful for providing additional
 150 alignment constraints or creating panoramic image mosaics.  (See also the
 151 description of the --follow option in the <a href="../alignment">alignment</a>
 152 section.)
 153
 154 <pre>
 155 --extend          Increase image extents to accommodate all pixel data.
 156 --no-extend       Don't increase extents; crop to original frame. [default]
 157 </pre>
 158
 159 <h2>Incremental output</h2>
 160
 161 By default, the output file is written every time a renderer completes an
 162 update cycle.  In order to suppress output until the final image is rendered,
 163 specify the --no-inc option.
 164
 165 <pre>
 166 --inc             Produce incremental output.  [default]
 167 --no-inc          Don't produce incremental output.
 168 </pre>
 169
 170 <h2>Pixel replacement</h2>
 171
 172 <p>When using the merging renderer, --replace indicates that each new frame
 173 should replace the corresponding region of the rendering, instead of being
 174 merged with data from previous frames.  This option was originally suggested by
 175 Jeff Treece for use in stabilization of video streams.  His approach to
 176 stabilization is outlined below.
 177
 178 <h3>Video Stabilization</h3>
 179
 180 <p>If the files
 181
 182 <pre>0.ppm, 1.ppm, ..., 9.ppm</pre>
 183
 184 represent frames from an unstabilized video stream, then the following sequence
 185 of commands may result in a stabilized sequence:
 186
 187 <pre>
 188 ale --replace         0.ppm 1.ppm 1.stable.ppm
 189 ale --replace  1.stable.ppm 2.ppm 2.stable.ppm
 190 ale --replace  2.stable.ppm 3.ppm 3.stable.ppm
 191 .
 192 .
 193 .
 194 ale --replace  8.stable.ppm 9.ppm 9.stable.ppm
 195 </pre>
 196
 197 <p>The resulting stabilized sequence would be:
 198
 199 <pre>0.ppm, 1.stable.ppm, 2.stable.ppm, ..., 9.stable.ppm</pre>
 200
 201 <h3>Option Syntax</h3>
 202
 203 <pre>
 204 --replace         Replace overlapping areas rather than merging.
 205 --no-replace      Do not replace.  [default]
 206 </pre>
 207
 208
 209 <br>
 210 <hr>
 211 <i>Copyright 2003 <a href="mailto:dhilvert@auricle.dyndns.org">David Hilvert</a></i>
 212 <p>Verbatim copying and distribution of this entire article is permitted in any medium, provided this notice is preserved.
 213
 214
 215 </body>
 216 </html>