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From Wikipedia

A suitable raster graphics editor shows transparency by a special pattern, e.g. a chessboard pattern.

  1. I wonder why complete transparency is shown as chessboard pattern? Is it chosen deliberately by people, or just a natural appearance of transparency under some circumstances?
  2. How shall one distinguish an image which is actually a chessboard from an image with complete transparency?

Thanks!

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  1. it's tradition.

  2. by inspecting the pixel values or superimposing the image over a background or by zooming in and observing that the chequerboard spacing is unaffected.

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Why is it a tradition? – Tim Jul 24 '12 at 11:48
4  
@Tim: for the same reasons that the Utah Teapot is a tradition. – RedGrittyBrick Jul 24 '12 at 11:59
3  
You can. Viewers with zoom functionality (e.g. mostly all) will not zoom into the chessboard pattern, while enlarging the image. – Jonas Wielicki Jul 24 '12 at 12:11
    
@JonasWielicki: thanks, answer updated accordingly. – RedGrittyBrick Jul 24 '12 at 12:17

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