comp.lang.idl-pvwave archive: archive

Home » Public Forums » archive » Re: Zooming in place

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Zooming in place [message #46126 is a reply to message #46125]

Mon, 31 October 2005 14:05

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Mon, 31 Oct 2005 10:15:29 -0700, David Fanning wrote:

> Pravish writes:
>
>> Zooming in place is one feature that does not seem to be popular with
>> IDL users. It is really strange that we are satisfied with the zoomed
>> image being in another window. That does not allow us to work with the
>> zoomed image. We can just view at the zoom image. I would like to zoom
>> on an image, in place and not in a separate window, and then work on
>> this image and if need be, zoom back. But, I am using a draw widget to
>> work with the image. That might seem to make things more complex.
>>
>> I have seen David's Zimage program and I think I could play around with
>> it and with some modifications, I will be able to use it.
>>
>> Any thoughts on this one?
>
> Zooming in place is one of those things that sound like a good idea until
> you start to implement it. Then you find it burdened with one constraint
> or another that make it more difficult to implement than you initially
> thought it was going to be.
>
> For example, if you allow the user to select the zoomed area, then you
> have problems of selection aspect ratio verses window aspect ratio. If you
> don't allow selection, then you have to determine how to allow the user to
> indicate selection, how much to zoom, etc.
>
> The biggest challenge, though, is going from a device coordinate system to
> the "data" coordinate system of the image in the zoomed window. It it not
> trivial to figure out where exactly you are in the image when you are in a
> display window.
>
> Once you have figured all this out once or twice, it is not something you
> really want to do again. So I would advise writing an image object that
> can do it all for you. Your image will need the ability to set up both a
> "normal" and "zoomed" coordinate system. You will need, probably, both the
> original image and a "display" image. (You might be able to create this on
> the fly.) You will need a method that can convert a point in window space
> to an image coordinate (the image "data" space) and visa versa, which
> means you will need an image that knows where it is in the display window.

Just my $0.02 on the "best" algorithm for in-place zooming. My viewer
(which might be released one of these days) lets you select a zoom region
with a rubber-band, or just click to double the zoom. The final selected
region is zoomed up in integer multiples to maximally fill the display
window, and the rest of the window defaults to some neutral background
color. Single right clicks zoom you out one step, and double right-clicks
zoom you out "all the way". Works fairly well, in practice.

JD

Report message to a moderator

[Message index]

		Re: Zooming in place By: ronn on Thu, 03 November 2005 18:30
		Re: Zooming in place By: pravesh.subramanian on Thu, 03 November 2005 16:27
		Re: Zooming in place By: David Fanning on Wed, 02 November 2005 00:32
		Re: Zooming in place By: AJ on Wed, 02 November 2005 00:13
		Re: Zooming in place By: JD Smith on Tue, 01 November 2005 13:00
		Re: Zooming in place By: Rick Towler on Tue, 01 November 2005 11:50
		Re: Zooming in place By: David Fanning on Tue, 01 November 2005 08:50
		Re: Zooming in place By: AJ on Tue, 01 November 2005 08:20
		Re: Zooming in place By: Paul Van Delst[1] on Tue, 01 November 2005 06:18
		Re: Zooming in place By: David Fanning on Mon, 31 October 2005 18:21
		Re: Zooming in place By: Rick Towler on Mon, 31 October 2005 16:11
		Re: Zooming in place By: Paul Van Delst[1] on Mon, 31 October 2005 14:38
		Re: Zooming in place By: JD Smith on Mon, 31 October 2005 14:05
		Re: Zooming in place By: David Fanning on Mon, 31 October 2005 10:09
		Re: Zooming in place By: pravesh.subramanian on Mon, 31 October 2005 09:37
		Re: Zooming in place By: David Fanning on Mon, 31 October 2005 09:15
		Re: Zooming in place By: David Fanning on Thu, 03 November 2005 18:42

Previous Topic:	Re: Error in Object
Next Topic:	point datasets in ENVI: some potentially useful routines and an ROI problem

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Wed Oct 08 14:58:04 PDT 2025

Total time taken to generate the page: 0.00249 seconds