| digitize a curve from an image [message #21178] |
Fri, 18 August 2000 00:00  |
Kristian Kjaer
Messages: 58
Registered: June 1998
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I have a gif file (B/W only, no greys or colours) showing a line graph.
Now I would like to get hold of the x,y arrays represented by the curve.
Has anyone written something to do that already?
The coordinate axes are a little skewed in the image (originally
scanned).
Thanks for any help, Kristian
--------------------------
Kristian Kjær, Physics Dept., Risø Natl. Laboratory, Denmark
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| Re: digitize a curve from an image [message #21360 is a reply to message #21178] |
Fri, 18 August 2000 00:00  |
Kristian Kjaer
Messages: 58
Registered: June 1998
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Member |
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> Kristian Kjær wrote:
>> I have a gif file (B/W only, no greys or colours) showing a line
>> graph. Now I would like to get hold of the x,y arrays represented by
>> the curve.
>> The coordinate axes are a little skewed in the image
Med Bennett wrote:
> Here is a link to the program I was thinking of -
> http://www.nikhef.nl/user/keeshu/datathief/
Thanks a lot. Looks good; but for some reason it won't display my
images. (3288x2412x2 gif and 8520x6392x2 gif).
Also, I realize, the curve is not a continuous line of pixes (rendered
with dots or dashes, I think), so the program's trace function wouldn't
work. I probably have to use the mouse to define the curve.
So I'm still interested in any pointers.
- Kristian
Kristian Kjær, Physics Dept., Risø Natl. Laboratory, Denmark
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| Re: digitize a curve from an image [message #21363 is a reply to message #21178] |
Fri, 18 August 2000 00:00 |
John D. Sample
Messages: 11
Registered: August 1999
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Junior Member |
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Yes and there is another called "Digigraf" (freeware) by W.S. Tortike in
Alberta. It works by clicking on the origin then clicking the ends of the x
and y axes, entering the scale, and then clicking on points of the graph.
Again, its a Mac application...I don't know if a PC version exists.
Chip
----------
In article <399D552E.F1297818@indra.com>, Med Bennett <mbennett@indra.com>
wrote:
> Here is a link to the program I was thinking of - ominously named
> "Datathief".
>
> http://www.nikhef.nl/user/keeshu/datathief/
>
> Kristian Kj�r wrote:
>>
>> I have a gif file (B/W only, no greys or colours) showing a line graph.
>> Now I would like to get hold of the x,y arrays represented by the curve.
>> Has anyone written something to do that already?
>> The coordinate axes are a little skewed in the image (originally
>> scanned).
>>
>> Thanks for any help, Kristian
>> --------------------------
>> Kristian Kj�r, Physics Dept., Ris� Natl. Laboratory, Denmark
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| Re: digitize a curve from an image [message #21371 is a reply to message #21178] |
Fri, 18 August 2000 00:00 |
mchinand
Messages: 66
Registered: September 1996
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Member |
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It's not any IDL program, but check out g3data at:
http://www.physics.helsinki.fi/~frantz/software/g3data.html
It should do what you want. It looks like it was mainly written for Linux
but it will probably compile under most Unix platforms if you have gtk
installed. I have compiled it for IRIX 6.5
Hope that helps,
--Mike
In article <399D1679.CE7E5633@Risoe.DK>,
Kristian Kj�r <Kristian.Kjaer@Risoe.DK> wrote:
> I have a gif file (B/W only, no greys or colours) showing a line graph.
> Now I would like to get hold of the x,y arrays represented by the curve.
> Has anyone written something to do that already?
> The coordinate axes are a little skewed in the image (originally
> scanned).
>
> Thanks for any help, Kristian
> --------------------------
> Kristian Kj�r, Physics Dept., Ris� Natl. Laboratory, Denmark
--
--
Michael Chinander University of Chicago
m-chinander@uchicago.edu (773)834-5101 (Voice) (773)702-0371 (Fax)
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| Re: digitize a curve from an image [message #21372 is a reply to message #21178] |
Fri, 18 August 2000 00:00 |
Med Bennett
Messages: 109
Registered: April 1997
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Senior Member |
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I know that there is at least one standalone program that is supposed to
do this, I think it's a Mac thing. Failing that, I guess I would
digitize it in device coordinates, and then use POLYWARP to try to
recover the data coordinates. I'll see if I can find the name of that
program. Good luck,
Med
Kristian Kj�r wrote:
>
> I have a gif file (B/W only, no greys or colours) showing a line graph.
> Now I would like to get hold of the x,y arrays represented by the curve.
> Has anyone written something to do that already?
> The coordinate axes are a little skewed in the image (originally
> scanned).
>
> Thanks for any help, Kristian
> --------------------------
> Kristian Kj�r, Physics Dept., Ris� Natl. Laboratory, Denmark
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| Re: digitize a curve from an image [message #21383 is a reply to message #21178] |
Fri, 25 August 2000 00:52 |
marc schellens[1]
Messages: 183
Registered: January 2000
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Senior Member |
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>
> Two possible solutions (aside from a request for the digital
> data):
> 1. get a bigger monitor
> 2. scan the image in a lower resolution so it fits onto your
> screen (or use photoshop or the likes to resample the image into
> a lower resolution)
>
Or 3. use a scrolling base around your draw widget.
cheers,
:-) marc
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| Re: digitize a curve from an image [message #21405 is a reply to message #21178] |
Wed, 23 August 2000 00:00 |
Kristian Kjaer
Messages: 58
Registered: June 1998
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Member |
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David Fanning wrote:
> I wouldn't be at all surprised to hear that Kristian *himself*
> is the author of the figure. That's how it usually works,
> in my experience, anyway. :-)
>
> Cheers, David
Pretty close! - Kristian
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| Re: digitize a curve from an image [message #21406 is a reply to message #21178] |
Wed, 23 August 2000 00:00 |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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Pavel Romashkin (promashkin@cmdl.noaa.gov) writes:
> I am beginning to wonder, maybe it is worth contacting the authors of
> the figure and get the data from them in the digital form?
I wouldn't be at all surprised to hear that Kristian *himself*
is the author of the figure. That's how it usually works,
in my experience, anyway. :-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
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| Re: digitize a curve from an image [message #21407 is a reply to message #21178] |
Wed, 23 August 2000 00:00 |
Kristian Kjaer
Messages: 58
Registered: June 1998
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Member |
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Pavel Romashkin wrote:
>
> I am beginning to wonder, maybe it is worth contacting the authors of
> the figure and get the data from them in the digital form? No matter
> what you do with the image, digitizing will be limited in precision.
> Just tried to be helpful.
> Cheers, Pavel
Of course. Morten who calculated the curves had a crash of his harddisk.
He has to reconfigure before he can recalculate the curve from raw data
backed-up on tape. He also left for holidays. We're talking several
weeks here. I wanted to move quicker than that, even at some loss of
precision.
Best regards, Kristian
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| Re: digitize a curve from an image [message #21414 is a reply to message #21178] |
Wed, 23 August 2000 00:00 |
Martin Schultz
Messages: 515
Registered: August 1997
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Senior Member |
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Kristian Kjaer wrote:
>
> Thanks for your replies.
>
> One problem I had was that in all the programs the screen resolution was
> a limiting factor; my scanned images had many more pixels than would fit
> on the screen.
> I thought of hacking something in IDL with
>
> tvscl,image
> while ... do cursor,x,y ; click to get the coord frame
> while ... do cursor,x,y ; click to get the curve
> polywarp, ... ; to get the coord. transformation (as
> suggested).
>
> but then I realized that again the screen resolution would limit the
> result. Apparently, what I'd need is a rowing zoom window for exploring
> the image.
>
> In the end I decided to settle for screen resolution.
>
> - Kristian
> -------------
> Kristian Kj�r, Physics Dept., Ris� Natl. Laboratory, Denmark
>
> Kristian Kj�r wrote:
>>
>> I have a gif file (B/W only, no greys or colours) showing a line graph.
>> Now I would like to get hold of the x,y arrays represented by the curve.
>> Has anyone written something to do that already?
>> The coordinate axes are a little skewed in the image (originally
>> scanned).
>>
>> Thanks for any help, Kristian
Two possible solutions (aside from a request for the digital
data):
1. get a bigger monitor
2. scan the image in a lower resolution so it fits onto your
screen (or use photoshop or the likes to resample the image into
a lower resolution)
Martin
--
[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[ [[[[[[[
[[ Dr. Martin Schultz Max-Planck-Institut fuer Meteorologie
[[
[[ Bundesstr. 55, 20146 Hamburg
[[
[[ phone: +49 40 41173-308
[[
[[ fax: +49 40 41173-298
[[
[[ martin.schultz@dkrz.de
[[
[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[ [[[[[[[
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| Re: digitize a curve from an image [message #21420 is a reply to message #21178] |
Tue, 22 August 2000 00:00 |
promashkin
Messages: 169
Registered: December 1999
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Senior Member |
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I am beginning to wonder, maybe it is worth contacting the authors of
the figure and get the data from them in the digital form? No matter
what you do with the image, digitizing will be limited in precision.
Just tried to be helpful.
Cheers,
Pavel
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| Re: digitize a curve from an image [message #21422 is a reply to message #21178] |
Tue, 22 August 2000 00:00 |
Kristian Kjaer
Messages: 58
Registered: June 1998
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Member |
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Thanks for your replies.
One problem I had was that in all the programs the screen resolution was
a limiting factor; my scanned images had many more pixels than would fit
on the screen.
I thought of hacking something in IDL with
tvscl,image
while ... do cursor,x,y ; click to get the coord frame
while ... do cursor,x,y ; click to get the curve
polywarp, ... ; to get the coord. transformation (as
suggested).
but then I realized that again the screen resolution would limit the
result. Apparently, what I'd need is a rowing zoom window for exploring
the image.
In the end I decided to settle for screen resolution.
- Kristian
-------------
Kristian Kjær, Physics Dept., Risø Natl. Laboratory, Denmark
Kristian Kjær wrote:
>
> I have a gif file (B/W only, no greys or colours) showing a line graph.
> Now I would like to get hold of the x,y arrays represented by the curve.
> Has anyone written something to do that already?
> The coordinate axes are a little skewed in the image (originally
> scanned).
>
> Thanks for any help, Kristian
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