Naked Science Forum
Non Life Sciences => Geek Speak => Topic started by: RD on 13/10/2008 08:50:51
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I applied an edge-finding algorithm (difference of Gaussians) to a jpeg image.
It found the edges I was interested in but it also detected the edges of the jpeg artefacts:
adding an unwanted graph-paper-like grid to the processed image.
I believe software exists which can remove jpeg artefacts from my original image,
(and consequently may avoid the creation of the grid in the processed image).
Would anyone who has used such a jpeg artifact removal tool please recommend it here.
I would prefer a “stand alone” programme (not "plug-in"), compatible with Vista ,
freeware, or modestly priced (£10-£20).
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I use Gimp for artifact removal, no grid added. By experimenting you can achieve good results.
http://www.gimp.org/windows/
Irfanview is much smaller, mainly for photo's and also plays music files but as a viewer its very good.
http://www.irfanview.com/
I use Irfanview a great deal as it does quite a lot of things such as batch processing, jpg lossless rotation, red-eye reduction, colour enhance etc. I also use it for a slide show screensaver.
Both are a free.. [:)]
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I use Gimp for artifact removal, no grid added. By experimenting you can achieve good results.
http://www.gimp.org/windows/
Thanks TMM. I have used blur followed by sharpen on GIMP to lessen jpeg artifacts.
However I have read that there are tools to remove these artifacts which produce better results than manually blurring-then-sharpening the image.
My copy of GIMP is about a year old. Has the latest version of GIMP got a tool specifically for removing jpeg artifacts ?
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Gimp does not have a single dedicated artifact removal tool. It does have various tools under the filters tab and you probably have already been using them. Noise removal, despeckle etc.
The only other one I know of is in Photoshop but that package is expensive.
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Sorry I can't recommend any particular software.
The main JPEG artifacts are "Blocking" (JPEG codes images in 8x8 or 16x16 pixel blocks) and "mosquito noise" (dotty or "ringing" artifacts around sharp edges).
Blocking artifacts fall on horizontal and vertical 8- (or 16-) pixel boundaries, and with that knowledge it should be possible to fudge them without introducing too many new problems. The mosquito issue is probably harder to deal with - the coding has thrown away coefficients and you can't really guess what's missing.
As a general rule, newer JPEG coders give less artifacts for a given filesize than older (eg 10-year old) coders.
If you're doing image-processing you really ought to be working with uncompressed (or minimally compressed) if at all possible.
Another thought is that if the source of your images is a consumer digital camera (or video camera) these typically apply excessive sharpening, which creates ringing (edge-enhancement/halo-ing) artifacts at source and will in turn give the subsequent JPEG coder a harder time. On the better cameras there are ways and means to ease off this sharpening (you may have to select "custom" colour-processing or somesuch). If you turn off the sharpening, and turn off the "digital noise reduction" (and set a lower ISO rating eg 100 ASA and adjust exposure accordingly) you'll get images which are far more natural-looking and pleasing to the eye (in my opinion) and which should process/filter better.
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I have found a free jpeg artifact removal tool: a photoshop plug-in (also works on Irfanview) from Topaz labs...
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http://www.topazlabs.com/topazlabs/03products/topaz_dejpeg/gallery/02remove_jpeg_artifacts/index.html
I shouldn't look a gift horse in the mouth, (it is free), but as you can see it can introduce an unintended oil-paint effect.
If anyone knows of another (better ?) jpeg artifact removal tool please post a link here, (ideally with a before/after example).
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This may not be ideal, as it's a photoshop CS2+ plug in, but it seems to do the job you're after...
Alien Skin - Image Doctor
Before/After at the bottom of this page:
http://www.alienskin.com/imagedoctor/idoc_filters.aspx
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Thanks RD, not noticed that one before and it works with irfanviw as well!
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This may not be ideal, as it's a photoshop CS2+ plug in, but it seems to do the job you're after...
Alien Skin - Image Doctor
Before/After at the bottom of this page:
http://www.alienskin.com/imagedoctor/idoc_filters.aspx
The effects of the "Image Doctor 2" jpeg repair filter do look better than the freebee from Topaz Labs,
but at $199 the Image Doctor from Alien Skin is beyond my budget.
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There's a 30 day demo though, if it's just for an individual project...
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I've had a go with the Topaz labs free "DeJpeg" plug-in on a photo of ferrofluid...
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It's not too bad, although this subject does suit an oily rendition.