Search found 109 matches

by rnbc
2012-12-06T09:11:27-07:00
Forum: Digital Image Processing
Topic: Image resizing with LCD sub-pixel awareness (aka ClearType)
Replies: 18
Views: 57919

Re: Image resizing with LCD sub-pixel awareness (aka ClearTy

henrywho, as I said before this is only useful as an output technology. It's not meant to be used to prepare images beforehand. We are doing that as a proof of concept only, but that's not how it makes sense to use. For example, perhaps the browser should be doing it when presenting large images, or...
by rnbc
2012-04-04T10:04:17-07:00
Forum: Digital Image Processing
Topic: Better JPEG quantization tables?
Replies: 84
Views: 177714

Re: Better JPEG quantization tables?

You might get better results, relative to the standard tables, by restricting your search to a certain set of image types. For example, I've heard about a guy that made an optimized set of tables for face image compression, and managed to get less than half the size for the same perceptible image qu...
by rnbc
2012-02-21T17:01:02-07:00
Forum: Digital Image Processing
Topic: Better JPEG quantization tables?
Replies: 84
Views: 177714

Re: Better JPEG quantization tables?

Ok, I'll wait :D
by rnbc
2012-02-21T05:24:28-07:00
Forum: Digital Image Processing
Topic: Better JPEG quantization tables?
Replies: 84
Views: 177714

Re: Better JPEG quantization tables?

Human visual system is more sensitive to defects in linear features, but not specifically horizontal or vertical. It just happens monitors are poor at displaying such features at an angle, so it happens horizontal/vertical gets better representation and is better seen and evaluated. Just rotate your...
by rnbc
2012-02-20T03:48:59-07:00
Forum: Digital Image Processing
Topic: Better JPEG quantization tables?
Replies: 84
Views: 177714

Re: Better JPEG quantization tables?

Nicolas, why don't you post to a page a set of images compressed with different tables (in png perhaps?) so that we can easily evaluate the results. Anyway, I'll try to evaluate your tables today or tomorrow. No guarantees, but I'll try. Is there a standard set of images used for evaluation we could...
by rnbc
2012-02-16T11:26:08-07:00
Forum: Digital Image Processing
Topic: Better JPEG quantization tables?
Replies: 84
Views: 177714

Re: Better JPEG quantization tables?

Without a large set of people for testing and a large set of viewing conditions I think trying to improve on the standard is impossible... Only with statistics and intensive testing could you claim to have arrived at a better set of quantization tables. Otherwise, as a pet project, I have nothing ag...
by rnbc
2012-02-16T10:08:45-07:00
Forum: Digital Image Processing
Topic: Better JPEG quantization tables?
Replies: 84
Views: 177714

Re: Better JPEG quantization tables?

How are you measuring quality? Perceptual? Numeric Error (standard deviation)? And if "perceptual", on which output device, under which conditions? Just questions...
by rnbc
2012-02-16T09:10:42-07:00
Forum: Digital Image Processing
Topic: Colorspace handling and the future of ImageMagick.
Replies: 15
Views: 41668

Re: Colorspace handling and the future of ImageMagick.

As long as you can stil work with channels and values "as is", which is important for those using imagemagick as a research tool, I would say all operators could be made colorspace aware, and work differently for different colorspaces and different luminance functions. How to make colorspace support...
by rnbc
2012-02-16T08:36:50-07:00
Forum: Digital Image Processing
Topic: Image resizing with LCD sub-pixel awareness (aka ClearType)
Replies: 18
Views: 57919

Re: Image resizing with LCD sub-pixel awareness (aka ClearTy

towolf, it should be trivial to make a perl script invoking imagemagick (or using perlmagick) with the right parameters. Do you want me to do it? :) Say, such a script could take screen dimensions and downsample an entire image collection for slideshow viewing with the best quality possible, fitting...
by rnbc
2011-10-11T09:09:40-07:00
Forum: Users
Topic: DICOM black artifacts
Replies: 28
Views: 43009

Re: DICOM black artifacts

Try executing under qemu with your OS of choice. That way others will be able to exactly reproduce your environment, even if you have to post the qemu image...
by rnbc
2011-10-02T06:05:18-07:00
Forum: Users
Topic: DICOM black artifacts
Replies: 28
Views: 43009

Re: DICOM black artifacts

I would say there is a overflow bug somewhere in the pipeline...

Maybe you can avoid it by using the HDRI enabled version of ImageMagick (involves a recompile) since it uses floating point and allows whiter than white colors.
by rnbc
2011-09-30T13:03:43-07:00
Forum: Digital Image Processing
Topic: Image resizing with LCD sub-pixel awareness (aka ClearType)
Replies: 18
Views: 57919

Re: Image resizing with LCD sub-pixel awareness (aka ClearTy

This guys describe something similar to what I'm doing, and was published in 2002. http://ics.ele.tue.nl/~dehaan/pdf/90_jsid2003.pdf Including the aliasing vs sharpness tradeoffs. Very interesting... I'm reinventing the wheel because someone forgot it long ago... I know of no programs actively doing...
by rnbc
2011-09-30T12:54:06-07:00
Forum: Digital Image Processing
Topic: Image resizing with LCD sub-pixel awareness (aka ClearType)
Replies: 18
Views: 57919

Re: Image resizing with LCD sub-pixel awareness (aka ClearTy

SmudgeToolKitteh, quite frankly I've never seen this applied to images except for Jason S. My method is different since it also accepts a controllable amount of aliasing (just use more or less gaussian blur, or a specific kernel for filtering in the intermediate steps), benefiting sharpness. It's al...
by rnbc
2011-09-24T09:11:56-07:00
Forum: Digital Image Processing
Topic: Image resizing with LCD sub-pixel awareness (aka ClearType)
Replies: 18
Views: 57919

Re: Image resizing with LCD sub-pixel awareness (aka ClearTy

Even sharper, while accepting aliasing in both axis. This aliasing can be controlled using blur and keeping the final ratio at 2:1 vertically and 3:1 horizontally. A different blur factor for each axis might be needed for best results. This must me tested by trial and error, since best results vary ...
by rnbc
2011-09-18T19:24:48-07:00
Forum: Users
Topic: Exif bug when reading TIFFs?
Replies: 21
Views: 32794

Re: Exif bug when reading TIFFs?

Interesting...

I can see version 7 will support multispectral images and possibly colored transparency, am I right? :)