New in Wolfram Mathematica 6: Extended Array Operations  previous | next 
Conveniently Replace Elements in Arrays
Mathematica 6 enhances ReplacePart to allow a convenient syntax for arbitrary index lists with symbolic patterns.
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Click for copyable input
ArrayPlot[

 ReplacePart[Rasterize["ABC", "RGBColor", ImageSize -> 50], 

  Table[RandomInteger[{1, 50}, 2] -> Gray, {500}]]]
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