| Re: Incomplete ouput PNG files. [message #78699 is a reply to message #78698] |
Thu, 15 December 2011 02:22   |
lecacheux.alain
Messages: 325
Registered: January 2008
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Senior Member |
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On 14 déc, 23:21, David Fanning <n...@dfanning.com> wrote:
> Mark Piper writes:
>> This is a slightly different workflow, but could you please try setting
>> the BUFFER keyword in your call to IMAGE? E.g.,
>
>> p = image(data, /buffer)
>> p.save, 'this_image.png'
>> p.close
>
>> The graphic will be rendered in an offscreen buffer. I have a hunch that
>> this may help, since this feels like a tricky (to me, at least) X server
>> issue.
>
> I was curious to see how Coyote Graphics output would
> stack up against the output from these function graphics
> routines. But I wanted to be able to compare apples
> to apples, so I spent some time today modifying the
> Coyote Graphic routines so that I could control
> the output file parameters, and in particular, the
> resolution of the output.
>
> This is now done with cgWindow_SetDefs, just like
> it is for cgWindow. In my first comparisons, I noticed
> that the function graphics output was a bit darker
> than the Coyote Graphics output, so I defined a new
> keyword for PS_START, called DEFAULT_THICKNESS so that
> I can set the default line and character thickness for
> the PostScript output. I set the default to 3 to better
> match the function graphics output.
>
> Anyway, you will need an updated Coyote Library to run
> the program described, if you want to play around with this:
>
> http://www.idlcoyote.com/programs/zip_files/coyoteprograms.z ip
>
> This is tagged release 1.5.1, if you are using the Subversion
> repository.
>
> So, here is the program. I'm doing a simple plot command and
> saving the data as JPEG, PNG, and encapsulated PostScript files.
> (Coyote Graphics routines actually produce landscape PostScript
> files, which function graphics commands do not, so I am using
> encapsulated PostScript for my comparisons. Both will produce
> encapsulated output in Portrait mode.) I've saved the files
> at 600 dpi, 300 dpi and 75 dpi.
>
> I was careful to make sure I was using the same size window
> in both cases, 640 in X and 512 in Y.
>
> In general, I can't really tell much difference in the output.
> The title is set too close to the plot, but that has always
> been the case in direct graphics. That is about the only
> difference that really jumps out at me.
>
> A couple of odd things. The PostScript files are all the
> same size at every resolution. They are 11KB for Coyote
> Graphics output and 9 KB for function graphics output.
> Here is a table of values in KM. The size values are
> a comparison of the output. You can see that Coyote
> Graphics routines are consistently larger in dimensions,
> but smaller in total size. I don't know how to account for
> this. In any case, the visual output is comparable so
> I assume this is just a different way of setting the
> resolution. The XSIZE and YSIZE dimensions are for the
> JPEG file in every case, but the comparable PNG file
> has the same dimensions.
>
> EPS JPEG PNG XSIZE YSIZE
> cg75 11 39 63 717 573
> fg75 9 39 33 667 534
>
> cg300 11 227 46 2867 2292
> fg300 9 254 165 2669 2135
>
> cg600 11 568 131 5733 4583
> fg600 9 736 379 5339 4271
>
> I guess the bottom line is that I am EXTREMELY happy
> with the performance of Coyote Graphics in this
> comparison. Not only are my routines faster, but the output
> I care about is essentially identical to the output
> from function graphics routines. As an added bonus,
> my output files are significantly smaller at high
> resolution. I don't know why this would be the case.
>
> Here is the code I used, if you want to try this for
> yourself:
>
> http://www.idlcoyote.com/misc/compare_resolution.pro
>
> Cheers,
>
> David
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming:http://www.idlcoyote.com/
> Sepore ma de ni thui. ("Perhaps thou speakest truth.")
I could note that the "p.save"d PNG file size is depending on the
window size when using an open NG graphics window. I guess that the
saved graphic file will depend on the off-screen buffer size when
BUFFER keyword is used. But what is this size? I could not find the
answer in 8.1 documentation. Maybe larger that Coyote's one
(IDLgrBuffer has a maximum size of 82192x8192) ?
alx.
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