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How to determine the mask portion (or unwanted region) from an image and rotate for direction correction using IDL tools? [message #86924]

Fri, 13 December 2013 07:00

atmospheric physics is currently offline

atmospheric physics
Messages: 121
Registered: June 2010

Senior Member

Hello All,

I have a picture from sky imager which is direction corrected (i.e., N-S or E-W are not exactly top-bottom or right-left directions of the image!!!). The sky imager provides the hemispheric view of our sky and the image is framed in a circular disk. But there is some unwanted portion of the edges and the image is saved in as usual case of rectangular/ square type picture. I wanted to remove the unwanted portion (i.e., masking) and obtain only the circular portion of the image. Then basing on the solar position seen on the image, automatic rotation shall be applied to correct the image to the correct directions. I know how to do this manually for one single image ... but I have enumerable images. Can anyone suggest me if this is possible with IDL???

Thanks in advance...

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Re: How to determine the mask portion (or unwanted region) from an image and rotate for direction correction using IDL tools? [message #86925 is a reply to message #86924]

Fri, 13 December 2013 07:02

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Madhavan Bomidi writes:

> I have a picture from sky imager which is direction corrected (i.e., N-S or E-W are not exactly top-bottom or right-left directions of the image!!!). The sky imager provides the hemispheric view of our sky and the image is framed in a circular disk. But there is some unwanted portion of the edges and the image is saved in as usual case of rectangular/ square type picture. I wanted to remove the unwanted portion (i.e., masking) and obtain only the circular portion of the
image. Then basing on the solar position seen on the image, automatic rotation shall be applied to correct the image to the correct directions. I know how to do this manually for one single image ... but I have enumerable images. Can anyone suggest me if this is possible with IDL???

As far as I know, this is the purpose of FOR loops. ;-)

Cheers,

David

--
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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Re: How to determine the mask portion (or unwanted region) from an image and rotate for direction correction using IDL tools? [message #86926 is a reply to message #86925]

Fri, 13 December 2013 07:36

atmospheric physics
Messages: 121
Registered: June 2010

Senior Member

I know that FOR loops can handle applying the task on multiple files one after the other. The sky image will have sky color, white or grey colored cloud patches, and the edges with dark/black color. I wanted to mask this edges and have only the circular disk as my picture. How can we mask a colored image? Can you suggest if you have any posts on masking color images???

Thanks and regards

On Friday, December 13, 2013 4:02:50 PM UTC+1, David Fanning wrote:
> Madhavan Bomidi writes:
>
>
>
>> I have a picture from sky imager which is direction corrected (i.e., N-S or E-W are not exactly top-bottom or right-left directions of the image!!!). The sky imager provides the hemispheric view of our sky and the image is framed in a circular disk. But there is some unwanted portion of the edges and the image is saved in as usual case of rectangular/ square type picture. I wanted to remove the unwanted portion (i.e., masking) and obtain only the circular portion of the
>
> image. Then basing on the solar position seen on the image, automatic rotation shall be applied to correct the image to the correct directions. I know how to do this manually for one single image ... but I have enumerable images. Can anyone suggest me if this is possible with IDL???
>
>
>
> As far as I know, this is the purpose of FOR loops. ;-)
>
>
>
> Cheers,
>
>
>
> David
>
>
>
>
>
> --
>
> 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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Re: How to determine the mask portion (or unwanted region) from an image and rotate for direction correction using IDL tools? [message #86928 is a reply to message #86926]

Fri, 13 December 2013 08:15

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Madhavan Bomidi writes:

> I know that FOR loops can handle applying the task on multiple files one after the other. The sky image will have sky color, white or grey colored cloud patches, and the edges with dark/black color. I wanted to mask this edges and have only the circular disk as my picture. How can we mask a colored image? Can you suggest if you have any posts on masking color images???

As it happens, I wrote an article this week that does exactly that:

http://www.idlcoyote.com/map_tips/subimage.php

Cheers,

David

--
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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