line drawings to test downsizing methods

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NicolasRobidoux
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line drawings to test downsizing methods

Post by NicolasRobidoux » 2012-09-22T17:20:25-07:00

@Anthony, especially:
Do you have some line drawing images that you consider good to test line drawing downsizing?

NicolasRobidoux
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Re: line drawings to test downsizing methods

Post by NicolasRobidoux » 2012-09-22T17:37:54-07:00

I found one: Image
A first attempt. (I've not tried anything else. Just a first "go".)

Code: Select all

magick baron.jpg -colorspace RGB +sigmoidal-contrast 25 -define filter:window=Quadratic -distort resize 100x100 -sigmoidal-contrast 25 -colorspace sRGB baron.EWAQuadraticJincSig25.png
This gives:
Image
Are there tests of this kind of operation somewhere? So I can tell what's usually done and how well it fares?

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Re: line drawings to test downsizing methods

Post by NicolasRobidoux » 2012-09-22T17:43:26-07:00

Well: First attempt -> Thumbs down.
Here is the same filter through linear light as before, but without sigmoidization:
Image

NicolasRobidoux
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Re: line drawings to test downsizing methods

Post by NicolasRobidoux » 2012-09-22T17:47:32-07:00

With less sigmoidal contrast, namely 6 (down from 25, which is rather large, in my first attempt):
Image
Not particularly impressive either.
-----
OK, I'll do something else for a while.

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Re: line drawings to test downsizing methods

Post by NicolasRobidoux » 2012-09-22T17:50:35-07:00

One last try: Ginseng through linear light, no sigmoidization:
Image

Code: Select all

magick baron.jpg -colorspace RGB -define filter:window=Jinc -define filter:lobes=3 -resize 100x100 -colorspace sRGB baron.GinsengSig0.png


NicolasRobidoux
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Re: line drawings to test downsizing methods

Post by NicolasRobidoux » 2012-09-22T18:26:02-07:00

@Fred:
These are nice.
Thank you.

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fmw42
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Re: line drawings to test downsizing methods

Post by fmw42 » 2012-09-22T18:33:36-07:00

It takes a long time to download, but you might find that the color images in the testimages.zip set at http://sourceforge.net/projects/testimages/files/ to be useful for color images to downsample

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Re: line drawings to test downsizing methods

Post by henrywho » 2012-09-23T08:00:31-07:00

I prefer linear light with EWA lanczos3Sharpest

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Re: line drawings to test downsizing methods

Post by NicolasRobidoux » 2012-09-23T08:35:53-07:00

henrywho wrote:I prefer linear light with EWA lanczos3Sharpest
Thank you Henry for your opinion. Here is the result:
Image
Not that different, on this test image, than linear light (orthogonal) Ginseng, and also to linear light (orthogonal) Lanczos and Cosine (with the new 3-lobe Sinc default). It's different. Just not very different.
I've actually removed the suggestion that one may want to use sigmoidization when downsampling from the current draft of my recommendations: http://web.cs.laurentian.ca/nrobidoux/m ... colas.html
(And EWA Lanczos3Sharpest, which fares well in the tests of my grad student Adam Turcotte, was there from the beginning in the downsampling section, as an example of lowering the blur to get additional sharpness.)

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Re: line drawings to test downsizing methods

Post by henrywho » 2012-09-23T19:25:53-07:00

EWA Lanczos3Sharpest offers more pronounced darkness differences in the gray "areas".
EWA Langrange, at this round, hurts the picture because its strong dark-halos are darkening the lines too much.

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