| Re: Incomplete ouput PNG files. [message #78698 is a reply to message #78697] |
Thu, 15 December 2011 02:32   |
lecacheux.alain
Messages: 325
Registered: January 2008
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Senior Member |
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On 15 déc, 11:22, alx <lecacheux.al...@wanadoo.fr> wrote:
> 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.- Masquer le texte des messages précédents -
>
> - Afficher le texte des messages précédents -
sorry, please read 8192x8192 in my previous message.
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