| Re: How to make higher resolution GIF or JPEG image? [message #38061 is a reply to message #38060] |
Fri, 13 February 2004 14:03   |
Andrew Loughe
Messages: 9
Registered: October 1998
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Junior Member |
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Lawrence,
How about creating a tiff image, and then converting that to GIF?
Does that look any better?
Or a jpeg with quality=100.
Or is this approach like getting water out of a rock?
-Andy
Lawrence Bleau wrote:
> I am running IDL V5.4 on OpenVMS AXP V7.1-2. I cannot upgrade to a
> later version of IDL since it is no longer made for VMS (dumb move,
> but that's another thread). In fact, since IDL V5.4 doesn't generate
> GIF files, I may have to go back to an earlier version to get that
> capability. But I'm getting ahead of myself.
>
> I want to generate a GIF file with a raster-like plot in it. I know
> how to do this using the Z-buffer as a device (SET_PLOT,'Z'). All my
> experience with GIF plots on other systems, though, show they display
> with slightly jagged lines, as though made on a low-res plot (which
> GIF is, I suppose). I have seen, however, GIF plots made by other
> packages that have a great look: smooth curves and letters, no
> jaggies.
>
> I know how to vary the size of the output GIF file: the SET_RESOLUTION
> keyword to the DEVICE command. The problem is that this keyword only
> changes the *size* of the resultant GIF file, not its resolution. If
> I use this keyword, all I get is a large GIF file with jaggies. When
> viewed on a browser, that gives me a larger image. I want the image to
> stay the size that can be displayed on a normal browser window, just
> to have a higher resolution.
>
> Does anyone know of an IDL solution that'd work in V5.4?
>
> If there's none, I can create an alternate format, such as PostScript,
> that has the high resolution plots. I'd then have to convert it to
> GIF (simply because very few browsers, if any, interpret PS).
>
> Does anyone know of a way to convert PS to GIF? I read about
> Ghostscript and Ghostview, but the ftp site says they removed the GIF
> generation capabilities from the package due to licensing problems.
> Since we're going to be displaying these gif's on the web, that's
> probably not a way for us to go. Any other ideas?
>
> Lastly, a suggestion made here was to generate jpeg files instead of
> GIFs. Several questions here:
>
> 1) Is this technically a good way to go, since we're displaying line
> plots rather than pictures? I.e., could the "lossy" nature of jpeg's
> algorithm hurt my plot?
> 2) Since making jpeg's from IDL also involves the Z-buffer device,
> won't this have the same limitations as making a GIF file?
>
> For example of jpeg's with jaggies, see
> http://uleis.umd.edu/~bleau/x.jpg <-- default resolution
> http://uleis.umd.edu/~bleau/x2.jpg <-- used SET_RESOLUTION=[1000,1500]
>
> In particular, take a look at the characters used to label the axes.
> Even at higher resolution they look bad. And yes, I know jaggies are
> usually an artifact of the monitor. Only thing is, I've seen a GIF
> display on a monitor that *didn't* have jaggies, so I know it's
> possible.
>
> Thanks, all.
>
> Lawrence Bleau
> University of Maryland
> Physics Dept., Space Physics Group
> 301-405-6223
> bleau@umtof.umd.edu
--
----> please remove the word OMIT from the return address <----
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