Changes between Version 1 and Version 2 of libcaca/study/4


Ignore:
Timestamp:
12/22/2009 09:19:36 PM (16 years ago)
Author:
Sam Hocevar
Comment:

fix image links

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  • libcaca/study/4

    v1 v2  
    1111Here are the results of applying a gaussian HVS to an 8×8 Bayer dithered image, simply by convoluting the image with a gaussian blur filter. This process is also known as '''inverse halftoning'''. Different values of ''σ'' simulate what the eye sees from different distances. On the left ''σ = 1'', on the right ''σ = 2'':
    1212
    13 [[Image(source:/web/trunk/static/study/out/lena4-1-1.png,class="inline",alt="8×8 Bayer dither, gaussian HVS, σ = 1")]]
    14 [[Image(source:/web/trunk/static/study/out/grad4-1-1.png,class="inline",alt="8×8 Bayer dither, gaussian HVS, σ = 1 gradient")]]
    15 [[Image(source:/web/trunk/static/study/out/lena4-1-2.png,class="inline",alt="8×8 Bayer dither, gaussian HVS, σ = 2")]]
    16 [[Image(source:/web/trunk/static/study/out/grad4-1-2.png,class="inline",alt="8×8 Bayer dither, gaussian HVS, σ = 2 gradient")]]
     13[[Image(source:/web/trunk/www/study/out/lena4-1-1.png,class="inline",alt="8×8 Bayer dither, gaussian HVS, σ = 1")]]
     14[[Image(source:/web/trunk/www/study/out/grad4-1-1.png,class="inline",alt="8×8 Bayer dither, gaussian HVS, σ = 1 gradient")]]
     15[[Image(source:/web/trunk/www/study/out/lena4-1-2.png,class="inline",alt="8×8 Bayer dither, gaussian HVS, σ = 2")]]
     16[[Image(source:/web/trunk/www/study/out/grad4-1-2.png,class="inline",alt="8×8 Bayer dither, gaussian HVS, σ = 2 gradient")]]
    1717
    1818== 4.2. Direct binary search ==
    … …  
    3232Below is an example of the algorithm results. The HVS uses a 11×11 convolution kernel of the ''e<small><sup> -sqrt(x²+y²)</sup></small>'' function. The initial image is randomly thresholded, and pixels are processed in raster order. Iterations 1, 2 and 5 are shown:
    3333
    34 [[Image(source:/web/trunk/static/study/out/lena4-2-1.png,class="inline",alt="direct binary search, iteration 0")]]
    35 [[Image(source:/web/trunk/static/study/out/grad4-2-1.png,class="inline",alt="direct binary search, iteration 0 gradient")]]
    36 [[Image(source:/web/trunk/static/study/out/lena4-2-2.png,class="inline",alt="direct binary search, iteration 1")]]
    37 [[Image(source:/web/trunk/static/study/out/grad4-2-2.png,class="inline",alt="direct binary search, iteration 1 gradient")]]
    38 
    39 [[Image(source:/web/trunk/static/study/out/lena4-2-3.png,class="inline",alt="direct binary search, iteration 2")]]
    40 [[Image(source:/web/trunk/static/study/out/grad4-2-3.png,class="inline",alt="direct binary search, iteration 2 gradient")]]
    41 [[Image(source:/web/trunk/static/study/out/lena4-2-4.png,class="inline",alt="direct binary search, iteration 5")]]
    42 [[Image(source:/web/trunk/static/study/out/grad4-2-4.png,class="inline",alt="direct binary search, iteration 5 gradient")]]
     34[[Image(source:/web/trunk/www/study/out/lena4-2-1.png,class="inline",alt="direct binary search, iteration 0")]]
     35[[Image(source:/web/trunk/www/study/out/grad4-2-1.png,class="inline",alt="direct binary search, iteration 0 gradient")]]
     36[[Image(source:/web/trunk/www/study/out/lena4-2-2.png,class="inline",alt="direct binary search, iteration 1")]]
     37[[Image(source:/web/trunk/www/study/out/grad4-2-2.png,class="inline",alt="direct binary search, iteration 1 gradient")]]
     38
     39[[Image(source:/web/trunk/www/study/out/lena4-2-3.png,class="inline",alt="direct binary search, iteration 2")]]
     40[[Image(source:/web/trunk/www/study/out/grad4-2-3.png,class="inline",alt="direct binary search, iteration 2 gradient")]]
     41[[Image(source:/web/trunk/www/study/out/lena4-2-4.png,class="inline",alt="direct binary search, iteration 5")]]
     42[[Image(source:/web/trunk/www/study/out/grad4-2-4.png,class="inline",alt="direct binary search, iteration 5 gradient")]]
    4343
    4444Other HVS models can be used, giving very high quality results. Below are the results of DBS with the following HVS functions:
    … …  
    5757The iteration shown is number 5. More iterations would have improved the results even slightly more, but that would have been at the expense of performance:
    5858
    59 [[Image(source:/web/trunk/static/study/out/lena4-2-5.png,class="inline",alt="direct binary search, sigma = 1, iteration 5")]]
    60 [[Image(source:/web/trunk/static/study/out/grad4-2-5.png,class="inline",alt="direct binary search, sigma = 1, iteration 5 gradient")]]
    61 [[Image(source:/web/trunk/static/study/out/lena4-2-6.png,class="inline",alt="direct binary search, sigma = 1.5, iteration 5")]]
    62 [[Image(source:/web/trunk/static/study/out/grad4-2-6.png,class="inline",alt="direct binary search, sigma = 1.5, iteration 5 gradient")]]
    63 
    64 [[Image(source:/web/trunk/static/study/out/lena4-2-7.png,class="inline",alt="direct binary search, sigma = 2, iteration 5")]]
    65 [[Image(source:/web/trunk/static/study/out/grad4-2-7.png,class="inline",alt="direct binary search, sigma = 2, iteration 5 gradient")]]
    66 [[Image(source:/web/trunk/static/study/out/lena4-2-8.png,class="inline",alt="direct binary search, best HVS, iteration 5")]]
    67 [[Image(source:/web/trunk/static/study/out/grad4-2-8.png,class="inline",alt="direct binary search, best HVS, iteration 5 gradient")]]
     59[[Image(source:/web/trunk/www/study/out/lena4-2-5.png,class="inline",alt="direct binary search, sigma = 1, iteration 5")]]
     60[[Image(source:/web/trunk/www/study/out/grad4-2-5.png,class="inline",alt="direct binary search, sigma = 1, iteration 5 gradient")]]
     61[[Image(source:/web/trunk/www/study/out/lena4-2-6.png,class="inline",alt="direct binary search, sigma = 1.5, iteration 5")]]
     62[[Image(source:/web/trunk/www/study/out/grad4-2-6.png,class="inline",alt="direct binary search, sigma = 1.5, iteration 5 gradient")]]
     63
     64[[Image(source:/web/trunk/www/study/out/lena4-2-7.png,class="inline",alt="direct binary search, sigma = 2, iteration 5")]]
     65[[Image(source:/web/trunk/www/study/out/grad4-2-7.png,class="inline",alt="direct binary search, sigma = 2, iteration 5 gradient")]]
     66[[Image(source:/web/trunk/www/study/out/lena4-2-8.png,class="inline",alt="direct binary search, best HVS, iteration 5")]]
     67[[Image(source:/web/trunk/www/study/out/grad4-2-8.png,class="inline",alt="direct binary search, best HVS, iteration 5 gradient")]]
    6868
    6969== 4.3 Comparing dithering algorithms ==