| Re: map_image and latmin/latmax, lonmin/lonmax - edges or centres? [message #86054 is a reply to message #86052] |
Thu, 26 September 2013 10:11   |
Andy Sayer
Messages: 127
Registered: February 2009
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Senior Member |
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Right, I agree in principle, but sometimes you want to take images from different sources and warp them to a common map projection to make a direct comparison. And if there is a map_image function in IDL, one would hope that it would work in a manner similar to intuition and/or the documentation.
Andy
On Thursday, September 26, 2013 1:08:00 PM UTC-4, David Fanning wrote:
> David Fanning writes:
>
>
>
>> I think that is what is happening here. The five values of our image are
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>> analogous to the locations of five vertical lines that we are using to
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>> "separate" the colors. We can only separate them into four colors with
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>> five lines. So, I think this is just the way interpolation works.
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>
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> This is one reason, of course, why most people who work with images and
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> map projections would NEVER think of using Map_Proj_Image or Map_Image,
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> either. Interpolation fools around with your very hard to acquire and
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> expensive image pixel values.
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>
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> It makes MUCH more sense to associate a map projection with the image
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> itself. In other words, leave the image alone, and just associate the
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> map projection with the image. This allows you to annotate the image
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> with map information without actually changing the shape or pixel values
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> of the image itself.
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>
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> Cheers,
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>
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> David
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> --
>
> David Fanning, Ph.D.
>
> Fanning Software Consulting, Inc.
>
> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
>
> Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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