Search found 88 matches

by imaggie
2012-01-03T08:55:57-07:00
Forum: Digital Image Processing
Topic: proper scaling of the Jinc filter for EWA use
Replies: 234
Views: 424166

Re: proper scaling of the Jinc filter for EWA use

Thanks for the vips link (needs a www. BTW) .

I was not expecting you to dig the code just some thoughts on the DFT but if you're busy , 'nuff said.

Sorry I was forgetting that jinc is a convolution kernel in the EWA context. No DFT. So irrelevant to this thread.
by imaggie
2012-01-03T06:30:01-07:00
Forum: Digital Image Processing
Topic: proper scaling of the Jinc filter for EWA use
Replies: 234
Views: 424166

Re: proper scaling of the Jinc filter for EWA use

Hi Nicola, if you have time could you look at this post I sent to the bugs forum? Your expertise in maths may help clarify what IM is or isn't doing and whether it is correct. http://imagemagick.org/discourse-server/viewtopic.php?f=3&t=20102 If fft is in some way producing less than rigorous results...
by imaggie
2012-01-03T06:19:05-07:00
Forum: Digital Image Processing
Topic: proper scaling of the Jinc filter for EWA use
Replies: 234
Views: 424166

Re: proper scaling of the Jinc filter for EWA use

Yes, I think gamma is relevant. I was suggesting this to Fred in recent days w.r.t. deblur et al. Gamma is a non-linear transformation and so it will have an affect on the result. I would expect this to affect colour balance more than ringing/blurring. Is there some kind of statistic that IM could p...
by imaggie
2012-01-03T04:49:56-07:00
Forum: Bugs
Topic: FFT phase ?
Replies: 19
Views: 33931

FFT phase ?

Hi, I am having some doubts as to whether -fft is producing the correct phase data. (Or perhaps documentation is incomplete as to what it is _supposed_ to produce). I'm looking at the DFT of simple straight line segment that can be used to simulate a motion blur: http://www.fmwconcepts.com/imagemagi...
by imaggie
2012-01-03T00:04:26-07:00
Forum: Digital Image Processing
Topic: proper scaling of the Jinc filter for EWA use
Replies: 234
Views: 424166

Re: proper scaling of the Jinc filter for EWA use

Of course, it was right in front of me all the time !

Why don't we use some of the russian tarts that adorn my screen every time I visit this forum ??? :lol:
by imaggie
2012-01-02T23:58:41-07:00
Forum: Digital Image Processing
Topic: proper scaling of the Jinc filter for EWA use
Replies: 234
Views: 424166

Re: proper scaling of the Jinc filter for EWA use

the Kodac suite (24bit PNG) http://r0k.us/graphics/kodak/ has a girl in red hat that looks suitable. Preamble says images are "for unrestricted usage".

Image

Between the smooth flesh tones and freckles that should some provide fairly exacting tests.
by imaggie
2012-01-02T09:24:40-07:00
Forum: Digital Image Processing
Topic: proper scaling of the Jinc filter for EWA use
Replies: 234
Views: 424166

Re: proper scaling of the Jinc filter for EWA use

Well, blur=0.943159799432847711 is a tad sharper with all that that implies. More jaggies on tripod, sharper look overall, slightly more intense look of concentration for the cameraman. I think the most accurate is a straight jinc3 without the deblur. With blur=0.88549061701764 I see a bit of roughn...
by imaggie
2012-01-02T00:00:09-07:00
Forum: Digital Image Processing
Topic: proper scaling of the Jinc filter for EWA use
Replies: 234
Views: 424166

Re: proper scaling of the Jinc filter for EWA use

http://www.fmwconcepts.com/imagemagick/fourier_transforms/images/cameraman.png could I suggest you take a look at this as a test image. While not a block graphic, it does have high contrast edges and sharp diagonals which are useful picking up some defects in various filters. I just ran the followi...
by imaggie
2012-01-01T12:03:59-07:00
Forum: Digital Image Processing
Topic: proper scaling of the Jinc filter for EWA use
Replies: 234
Views: 424166

Re: proper scaling of the Jinc filter for EWA use

I would expect 2 lobe versions to be too soft. They are cropped too early and deviate too much from the idea function to be sharp. Be sure to give equal testing time to block graphics. Nice photos like rose: will be a lot less susceptible to harsh ringing and results may lead to conclusions that are...
by imaggie
2011-12-30T00:09:00-07:00
Forum: Bugs
Topic: bad error trapping could cause unexpected shell commands
Replies: 8
Views: 14729

Re: bad error trapping could cause unexpected shell commands

thanks for the clarification.

Do you have any comment on the subject of this thread, that premature abortion of command line parsing can cause basically arbitrary residual text to be executed by the shell?
by imaggie
2011-12-29T12:18:43-07:00
Forum: Users
Topic: roll and blur
Replies: 4
Views: 8859

Re: roll and blur

thanks, that gives me some homework for tonight ;) That looks like I should be able to do exactly what I want with a bit of digging. what did already was this wid=`identify -format "%w" $src` half=$(($wid/2)) blur=52 convert -gravity Center $src \ -roll +$half+0 \ -region 6%x100% -blur 3x$(($blur*${...
by imaggie
2011-12-29T05:28:08-07:00
Forum: Users
Topic: roll and blur
Replies: 4
Views: 8859

Re: roll and blur

Thanks I have managed to blur a +/-5% strip that I rolled to centre and then back afterwards, repeated in x and y. This drastically reduces ringing due to boundary discontinuities, however, it's very clumsy. what would be nearer to what is needed is a progressive blur, like a linear gaussian blur wi...
by imaggie
2011-12-29T05:16:15-07:00
Forum: Digital Image Processing
Topic: proper scaling of the Jinc filter for EWA use
Replies: 234
Views: 424166

Re: proper scaling of the Jinc filter for EWA use

Can't think of a good method at this time. The big problem is that images only store a interger from 0 to 2^16-1 (for IM Q16) and Jinc has negatives. You would need HDRI or some type of offset, to do it properly. One thing I could do is map Resampling filters to Convolve/Morphology Kernels! But tho...
by imaggie
2011-12-29T01:16:31-07:00
Forum: Digital Image Processing
Topic: proper scaling of the Jinc filter for EWA use
Replies: 234
Views: 424166

Re: proper scaling of the Jinc filter for EWA use

As a result of some testing using windowed jinc on deblur it appears that there is not one "best" choice , indeed windowing is not always advantageous. As I said elsewhere I think some more thought needs to go into why the window is there and what it is supposed to achieve rather than subjective emp...
by imaggie
2011-12-26T17:14:48-07:00
Forum: Bugs
Topic: bad error trapping could cause unexpected shell commands
Replies: 8
Views: 14729

Re: bad error trapping could cause unexpected shell commands

that's great news.

IM is really powerful but it's usefulness is severely reduced by the arcane commands. I'm sure a thorough restructuring of the CLI would make it much more accessible.

Looks like , by the time I master the current command set , it'll be out of date. LOL.