Changes between Version 1 and Version 2 of libcaca/study/3


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Timestamp:
08/07/2009 10:08:33 PM (15 years ago)
Author:
Sam Hocevar
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  • libcaca/study/3

    v1 v2  
    190190Damera-Venkata and Evans introduce '''block error diffusion''' ![23], which reuses traditional error diffusion methods such as Floyd-Steinberg but applies the same error value to all pixels of a given block. Only one error value is propagated, ''a+b+c+d'', which is the global error within the block:
    191191
    192 [[Image(source:/web/trunk/static/study/out/fig3-1-1.png,class="math",alt="Floyd-Steinberg")]]
    193   ⊗
    194 [[Image(source:/web/trunk/static/study/out/fig3-5-2b.png,class="math",alt="2×2 balanced matrix")]]
    195   =
    196 [[Image(source:/web/trunk/static/study/out/fig3-5-2.png,class="math",alt="2×2-expanded Floyd-Steinberg")]]
     192[[Image(source:/web/trunk/static/study/out/fig3-1-1.png,class="math",alt="Floyd-Steinberg")]] ⊗ [[Image(source:/web/trunk/static/study/out/fig3-5-2b.png,class="math",alt="2×2 balanced matrix")]] = [[Image(source:/web/trunk/static/study/out/fig3-5-2.png,class="math",alt="2×2-expanded Floyd-Steinberg")]]
    197193
    198194Here are the results using the previous pixel blocks:
    … …  
    217213The results on the vertical gradient indicate poor block-choosing. In order to improve it, we introduce a modified, weighted intra-block error distribution matrix, still based on the original Floyd-Steinberg matrix:
    218214
    219 [[Image(source:/web/trunk/static/study/out/fig3-1-1.png,class="math",alt="Floyd-Steinberg")]]
    220   ⊗
    221 [[Image(source:/web/trunk/static/study/out/fig3-5-5b.png,class="math",alt="weighted 2×2 matrix")]]
    222   =
    223 [[Image(source:/web/trunk/static/study/out/fig3-5-5.png,class="math",alt="weighted 2×2 propagation matrix")]]
     215[[Image(source:/web/trunk/static/study/out/fig3-1-1.png,class="math",alt="Floyd-Steinberg")]] ⊗ [[Image(source:/web/trunk/static/study/out/fig3-5-5b.png,class="math",alt="weighted 2×2 matrix")]] = [[Image(source:/web/trunk/static/study/out/fig3-5-5.png,class="math",alt="weighted 2×2 propagation matrix")]]
    224216
    225217The result still looks sharpened, but shows considerably less noise: