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Automatic interpolation / smoothing in TV?? [message #85533]

Thu, 15 August 2013 02:14

Jakob
Messages: 2
Registered: August 2013

Junior Member

Hello,

I would like to display an image with few pixels. When I use the TV command (either directly or through cgimage) I find the image is being "blurred", as if each pixel was being broken up in 8x8 cells and then values were being interpolated. For my specific purpose I want each pixel to have sharp edges.

I've searched the manuals but was not able to locate the reason for this behavior. I could plot each pixel separately using squares of appropriate size, but this seems unnecessarily clumsy?

Any hint on what I am missing would be greatly appreciated.
CJ

pro example

dens = [[7.0, 190.0, 391.0, 166.0, 6.0, 0.0],[0.0, 11.0, 63.0, 92.0, 9.0, 1.0],[0.0, 0.0, 2.0, 1.0, 0.0, 0.0]]

set_plot,'PS'
device, filename='example.ps', /color, /landscape

tv, dens, xsize=20000, ysize=10000

device, /close

end

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Re: Automatic interpolation / smoothing in TV?? [message #85534 is a reply to message #85533]

Thu, 15 August 2013 05:00

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Jakob writes:

> I would like to display an image with few pixels. When I use the TV command (either directly or through cgimage) I find the image is being "blurred", as if each pixel was being broken up in 8x8 cells and then values were being interpolated. For my specific purpose I want each pixel to have sharp edges.
>
> I've searched the manuals but was not able to locate the reason for this behavior. I could plot each pixel separately using squares of appropriate size, but this seems unnecessarily clumsy?
>
> Any hint on what I am missing would be greatly appreciated.

My guess would be you are looking at your file using Preview on a Mac.
It always shows the wrong thing. But, everywhere else this should look
like you expect it to look. :-)

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: Automatic interpolation / smoothing in TV?? [message #85536 is a reply to message #85533]

Thu, 15 August 2013 06:02

Jakob
Messages: 2
Registered: August 2013

Junior Member

Hi David,
thanks a lot for the answer.
Indeed, other programs show the right thing on plots generated with TV.
Meanwhile I had coded the same plot using the clumsy approach (loop over polyfill).
This does not trigger the blurring behavior in preview.
So it must have to do with the way the colored squares are described in the ps file and what preview thinks it has to do to make it "look nice".
Anyway, that solves the question.
Thanks,
CJ

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Re: Automatic interpolation / smoothing in TV?? [message #85542 is a reply to message #85536]

Thu, 15 August 2013 09:13

Phillip Bitzer
Messages: 223
Registered: June 2006

Senior Member

You can also turn off smoothing in Preview to see the "right" thing.

Preferences->PDF->Smooth text and line art.

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