Subject:
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Re: img2sticker: Convert images into .ldr stickers
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Newsgroups:
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lugnet.cad
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Date:
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Thu, 30 Jun 2005 14:54:21 GMT
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Viewed:
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2640 times
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Hmm, I don’t think so. Traditional antialiasing spreads the partial
pixel errors from a line (or edge) into the adjacent pixels. In order
to undo it you’d need to know where the line is, but that’s the very
information you’re trying to recover from the image.
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Strictly speaking though, (almost) any filter is invertible. Of course you do
need to know what the original filter was which is easier said than done.
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In this case you’re not working from an antialiased image, but rather
one that has been sampled by a scanner or a digital camera. There was
no antialiasing applied. They just save what they see, blended colors
and all.
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Although it even worse as the image has been stored a a jpeg which bleeds the
colours even more in its compression algorithm.
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I’m pretty certain they already have edge sharpening and unblur
convolution filters which should be useful for undoing some of the
blending, before converting to the closest ldraw colors.
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Yes but edge sharpening actually seems to make the antialiasing worse. If it
finds an ‘edge’ between the ‘real’ colour and its fake neighbour it tries to
exaggerate this. I suspect it has something to do with the frequency offsets in
Fourier space.
Will do,
Tim
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Message has 2 Replies:
 | | Re: img2sticker: Convert images into .ldr stickers
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| (...) Yeah, but if you think of line antialiasing as a sort of blur filter, you'll notice the convolution kernel is directional. The blurring occurs perpendicular to the direction of the line. This implies a different filter for each line segment on (...) (19 years ago, 30-Jun-05, to lugnet.cad, FTX)
| | | Re: img2sticker: Convert images into .ldr stickers
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| (...) That may be true, but antialiasing isn't a filter in that sense. When applied to computer-generated graphics, it's calculated during rendering using information that isn't available in the final image. When aplied during image scaling (...) (19 years ago, 30-Jun-05, to lugnet.cad, FTX)
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Message is in Reply To:
| | Re: img2sticker: Convert images into .ldr stickers
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| (...) Hmm, I don't think so. Traditional antialiasing spreads the partial pixel errors from a line (or edge) into the adjacent pixels. In order to undo it you'd need to know where the line is, but that's the very information you're trying to recover (...) (19 years ago, 30-Jun-05, to lugnet.cad, FTX)
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