Changes between Version 1 and Version 2 of libcaca/study/7


Ignore:
Timestamp:
12/22/2009 09:23:17 PM (14 years ago)
Author:
Sam Hocevar
Comment:

fix image links

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  • libcaca/study/7

    v1 v2  
    55Since we don’t have many images at our disposal, we will simply cut Lena into small chunks (called '''tiles''') and use these parts to create mosaics.  This is our '''tile database''':
    66
    7 [[Image(source:/web/trunk/static/study/out/lena7-0-1.png,class="inline",alt="Patterns taken from Lena")]]
     7[[Image(source:/web/trunk/www/study/out/lena7-0-1.png,class="inline",alt="Patterns taken from Lena")]]
    88
    99Generating a photomosaic consists in subdividing the original picture into ''x'' rectangular cells and find ''x'' tiles in the database (with or without duplicates, depending on the set of rules that is decided) so that when recombined the resulting image resembles the original picture.  By the way, this technique is covered by Runaway Technology Inc.’s [http://www.freepatentsonline.com/6137498.html U.S. patent 6137498] ![9].
    … …  
    1515One of the simplest image classification techniques is the storage of each tile’s '''average colour''' into a separate database that is used for best match lookups. Of course, this computation should be gamma-corrected:
    1616
    17 [[Image(source:/web/trunk/static/study/out/lena7-1-1.png,class="inline",alt="1 feature extracted from Lena patterns")]]
     17[[Image(source:/web/trunk/www/study/out/lena7-1-1.png,class="inline",alt="1 feature extracted from Lena patterns")]]
    1818
    1919When creating the mosaic, we then only need to check the average colour instead of comparing each pixel one by one. Below is the result of the technique applied on a portion of the Lena picture:
    2020
    21 [[Image(source:/web/trunk/static/study/out/lena7-1-2.png,class="inlinetop",alt="Lena (detail)")]]
    22 [[Image(source:/web/trunk/static/study/out/lena7-1-3.png,class="inline",alt="Mosaic created from Lena’s detail")]]
     21[[Image(source:/web/trunk/www/study/out/lena7-1-2.png,class="inlinetop",alt="Lena (detail)")]]
     22[[Image(source:/web/trunk/www/study/out/lena7-1-3.png,class="inline",alt="Mosaic created from Lena’s detail")]]
    2323
    2424Better results can be achieved by storing '''four colour values''', one for each corner of the tile:
    2525
    26 [[Image(source:/web/trunk/static/study/out/lena7-1-4.png,class="inline",alt="4 features extracted from Lena patterns")]]
     26[[Image(source:/web/trunk/www/study/out/lena7-1-4.png,class="inline",alt="4 features extracted from Lena patterns")]]
    2727
    2828Having 12 values per tile (4 RGB triplets) is still a lot less than the original count of 3072 (for 32×32 tiles), and the results show clear improvement. For instance the feathers-hat frontier is now a lot smoother:
    2929
    30 [[Image(source:/web/trunk/static/study/out/lena7-1-2.png,class="inlinetop",alt="Lena (detail)")]]
    31 [[Image(source:/web/trunk/static/study/out/lena7-1-5.png,class="inline",alt="Mosaic created from Lena’s detail")]]
     30[[Image(source:/web/trunk/www/study/out/lena7-1-2.png,class="inlinetop",alt="Lena (detail)")]]
     31[[Image(source:/web/trunk/www/study/out/lena7-1-5.png,class="inline",alt="Mosaic created from Lena’s detail")]]
    3232
    3333== 7.2. Error diffusion ==
    … …  
    3939TODO
    4040
    41 [[Image(source:/web/trunk/static/study/fig7-3-1.png,class="matrix",alt="ASCII art tiles")]]
     41[[Image(source:/web/trunk/www/study/fig7-3-1.png,class="matrix",alt="ASCII art tiles")]]