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? [OS 26/04/06] mod
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All settings generate black image

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? [OS 26/04/06] medianFilter
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Takes forever for radius > 10 (on large images)

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? [OS 26/04/06] scaleImage, sampleImage
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Only proportional scaling, think of other options for non-proportional 
scaling

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? [WH 26/04/06] rgb
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Instead of the logical flag "rgb" can we have a factor with
levels "rgb", "grayscale", this would be more extendable in case we
ever need additional image types

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? [WH 23/04/06] image.io.Rd - on image.read
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I think for our type of applications it would also be good to
be able to emit warnings or an error if the images have different sizes (because
in an HT screen, we expect them all to be the same size)
