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Re: Creating JPEG files [message #32424 is a reply to message #32423]

Wed, 09 October 2002 09:26

Med Bennett
Messages: 109
Registered: April 1997

Senior Member

Mike Jewison wrote:

> I have a short program which generates a 2D plot using a standard call
> to the PLOT procedure, displaying to the X-windows device. I would
> like to also have this plot dumped to a JPEG file for display on a web
> page. Although the plot looks just fine on the screen, when I issue
> the following command:
>
> WRITE_JPEG, JPEG_File, TVRD()
>
> the resultant JPEG file has very little contrast (i.e. it's basically
> near-black on black). I know the WRITE_JPEG procedure is better
> suited to images rather than plots, but is there (a) a better way to
> create a JPEG file of a plot rather than what I'm doing, or (b)
> another file format which IDL supports that would do a good job of
> creating a web-compatible image format? I used to use the WRITE_GIF
> format until IDL dropped support for it.
>
> Many thanks.
>
> - Mike

JPEG is really better suited for continuous tone graphics, i.e. photos,
shaded surface plots, etc. If you're trying to capture line art, ie. a
plot with only a few distinct colors, I believe it would be better to use
a GIF or PNG file format. The lossy JPEG compression does ugly things to
line graphics, and actually can create larger files than one of the
lossless graphics formats.

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[Message index]

		Re: Creating JPEG files By: Med Bennett on Wed, 09 October 2002 09:30
		Re: Creating JPEG files By: Med Bennett on Wed, 09 October 2002 09:26
		Re: Creating JPEG files By: David Fanning on Wed, 09 October 2002 08:30
		Re: Creating JPEG files By: David Fanning on Wed, 09 October 2002 08:19
		Re: Creating JPEG files By: R.Bauer on Wed, 09 October 2002 08:09
		Re: Creating JPEG files By: David Fanning on Wed, 09 October 2002 08:12

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