Changeset 2123


Ignore:
Timestamp:
Dec 6, 2007, 11:46:22 PM (12 years ago)
Author:
Sam Hocevar
Message:
  • A few additions to the ordered dithering. Started talking about void and cluster method.
File:
1 edited

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  • www/study/part2.html

    r2121 r2123  
    282282</p>
    283283
    284 <h3> 2.6. Recursive generation of dither matrices </h3>
     284<h3> 2.6. Supercell dithering </h3>
     285
     286<p> Supercell dithering consists in creating bigger dithering tiles
     287(supercells) from base tiles. One example is Victor Ostromoukhov’s
     288<b>CombiScreen</b> method. </p>
    285289
    286290<p> Just like Bayer matrices, non-rectangular tiles can be used to recursively
     
    316320</p>
    317321
    318 <p> Victor Ostromoukhov created a method called <b>CombiScreen</b> allowing
    319 for unlimited recursive tile creation. </p>
    320 
    321322<p> This example shows a tile resembling a Davis-Knuth dragon curve. Though
    322 the tile itself is beautiful, the results are not very different from a
    323 classic Bayer dither matrix: </p>
     323the tile itself is beautiful, due to the disposition of the cell values is
     324such that the resulting image is exactly the same as with a classic 8×8 Bayer
     325dither matrix: </p>
    324326
    325327<p style="text-align: center;">
     
    333335
    334336<p> Here are two consecutive iterations of the hexagonal tiling shown
    335 above: </p>
     337above. Since the area of the original tile is 10 cells, the first iteration
     338could display 11 different shades of grey. These iterations can display
     339respectively 31 and 91 shades: </p>
    336340
    337341<p style="text-align: center;">
     
    353357</p>
    354358
     359<h3> 2.7. Void and cluster method </h3>
     360
     361<p> Robert A. Ulichney’s <b>void and cluster method</b> is a very generic
     362method for dither array generation. It mainly targets huge matrices in order
     363to reduce artifacts caused by tiling. </p>
     364
     365<p> <b>FIXME</b>: efficient void and cluster (with Voronoï tesselation) is
     366hard to implement in Python, so no example yet. </p>
     367
    355368<div style="float: left;">
    356369   <a href="part1.html">Colour quantisation &lt;&lt;&lt;</a>
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