[Mapserver-users] Mapserver printing

[Lowell Filak]

The versions are MapServer 3.6.5 & 3.6.1.
The resolution is simpler than it first appears:
We take the intended output size, in this case 34x34 inches.
Then multiply it by the required resolution, in this case 180.
Using that we had MapServer generate a PNG that was 6120x6120.
We then scripted the ImageMagick "convert" command to convert the PNG to a TIFF.
Then (this part is still manually done) we use the ZehRaster Linux software that came with the plotter to send the TIFF to the plotter.
Inside the ZehRaster you actually specify the plot size, 34x34 in this case, and thereby specify the resolution.
The plotter still plots at something like 600dpi to the paper but the original image is really 180dpi.
Using the supplied software was the most reliable way we could find to pump the file to the plotter.
As far as having intermittent problems it most likely has more to do with the server load or memory usage.
I seem to recall a previous thread that pointed out that creating "large" images can require a considerable amount of system resources for  however long the process takes.
I would highly suggest watching the system resources and note what things look like when an image blows-up.
One unscientific & simple way of doing that is "top | grep <cgi_proccess_name>" and then run some requests.
Lowell F.

The following message was sent by "Zamil Murji" <Zamil.Murji at divestco.com> on Tue, 27 May 2003 14:18:39 -0600.

> Hi Lowell and the rest of the mapserver crowd,
> May I ask what version of Mapserver you're using? And how do you change the resolution of your image to 180 dpi?
> I had the same thought as you as to the html finishing but the image file is not finished. However after waiting upwards of a minute and trying to load the image specified in the source tag, it was still blank? Any other thoguht? It only happens about  10% of the time, but frequently enough to make me concerned.
> Any thoughts?
> 
> Zamil
> 
> -----Original Message-----
> From: Lowell Filak [mailto:lfilak at medinaco.org]
> Sent: Tuesday, May 27, 2003 2:10 PM
> To: Zamil Murji; mapserver-users at lists.gis.umn.edu
> Subject: Re: [Mapserver-users] Mapserver printing
> 
> 
> I'm not so sure that there is a limit.
> I have found that PNG works extremely well for large images and I've never had a problem with generating larger than 8.5x11 images w/ MapServer.
> I just finished working with one that is 10218x8814 (~34x30) (no it wasn't created with mapserver, but then that is why I am not sure there is a limit).
> Okay, I had to check it out... & MapServer reliably created a 6100x6100 (34x34 at 180dpi - which appears to be the max res. for that size that we can pump through ZehRaster to our plotter) PNG file (the browser wouldn't render it but Gimp opened it fine).
> As far as the blank PNG in the browser is concerned:
> What we have seen is that sometimes only part of the PNG is loaded, but that only seems to happen on one of the apps we have that tracks vehicles and loads a new map every 10-120 seconds.
> We have not tracked down why it happens but it would seem that the html is finished and loaded by the browser with the "img src" specified before the image file is actually finished.
> Lowell F.
> 
> The following message was sent by "Zamil Murji" <Zamil.Murji at divestco.com> on Fri, 23 May 2003 11:16:03 -0600.
> 
> > Hi,
> > 
> > We are currently trying to use mapserver to print images on an 8.5x11 inch paper using the web. Up to date we have been very successfull. However, we are now trying the next step - PLOTTING. I was wondering if anyone has any idea how to approach this issue. I read in the past that mapserver has a limit to the size of image that can be created, if so, how do I get around this. Any suggestions would be welcome.
> > 
> > Also, I noticed that when we started using png images all over our site. Sometimes they would come back empty. NO error messages from mapserver, just an empty image. If you refreshed the screen everything would start working again. The image would be displayed again. Anybody observe similar output? Once again, it happens randomly. Sometimes it works and sometimes it doesn't.
> > 
> > Zamil
> > 
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