Increase Clarity of WMS

Tue Apr 4 05:40:44 PDT 2006

Kyle -

I was looking at images like this one:

http://maps.kylemulka.com/imagemagick/floorplans/tiles/dude-1-1-5.png 

The image itself is indeed 256x256, but your MapServer WMS request is
asking for a source area much larger than 256x256 to be rendered into a
256x256 image.  The image quality degradation is coming from asking
MapServer to resample the source images to a lower output resolution.
You can get better quality resampling by using a (slower) tool to
preprocess the images.

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
Phone: +1 (978) 251-4242
Fax: +1 (978) 251-1396
ed at topozone.com

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Kyle Mulka
Sent: Tuesday, April 04, 2006 2:09 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: Re: [UMN_MAPSERVER-USERS] Increase Clarity of WMS

I'm pretty sure that all the tile images are in fact 256x256 and are
being rended that way by the browser. Do have a specific example of one
that's not like? Either generated by the javascript, or a tile in that
folder? Tools->Page Info->Media in Firefox will tell you what images are
currently loaded, including those loaded dynamically with javascript.

I'm thinking that I might have to use Google Maps itself to do
georeferencing. That way I can limit, or even eliminate the amount of
scaling and resampling that mapserver has to do. I'll give it a try next
week when I have some time. If someone has already done some
georeferencing with Google Maps and mapsever, let me know.

Thanks,

-Kyle

Ed McNierney wrote:

>Kyle -
>
>Well, if you increase the WIDTH and HEIGHT to 512 it will certainly 
>look better - and larger!
>
>You are taking a relatively large image and asking MapServer to shrink 
>it down for you for display.  I haven't time to decipher all the 
>JavaScript in there, but I suspect your "simply chopping up tiles using

>ImageMagick" example is actually generating HTML that tells the client 
>browser to stuff an oversized PNG into a smaller IMG tag.  Your 
>individual image tiles (from the floorplans/tiles/ directory) are 
>actually much larger images than your 
>http://maps.kylemulka.com/imagemagick/livedude.php displays.  Each 
>individual tile is 512x512 pixels, but your final output image is much 
>smaller than that.
>
>As a result, the quality of the output image may depend heavily on the 
>browser being used.  I think those 512x512 tiles are being displayed in

>IMG tags with HEIGHT and WIDTH properties set to a smaller value.  The 
>browser then squishes the images into the IMG space available.
>
>The image you're using is almost a worst-case scenario for MapServer.
>It's essentially a vector drawing that's been scanned as a raster
image.
>You've got lots of thin lines that easily appear and disappear at 
>different scale levels, depending on how the image is resampled.
>
>If you're going to use scanned line art in MapServer, you'll get the 
>best results by producing high-quality resampled versions (ImageMagick 
>is fine) at each specific scale/zoom level you'll want to use.  Then 
>force the user to only use one of your preselected zoom levels.  Make 
>sure that each image - when displayed - ends up exactly the same size 
>as the original image on your server.
>
>	- Ed
>
>Ed McNierney
>President and Chief Mapmaker
>TopoZone.com / Maps a la carte, Inc.
>73 Princeton Street, Suite 305
>North Chelmsford, MA  01863
>ed at topozone.com
>(978) 251-4242
>
>-----Original Message-----
>From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] 
>On Behalf Of Kyle Mulka
>Sent: Monday, April 03, 2006 7:30 AM
>To: MAPSERVER-USERS at LISTS.UMN.EDU
>Subject: Re: [UMN_MAPSERVER-USERS] Increase Clarity of WMS
>
>Here's one of the WMS tiles I'm using. I've tried stretching it using 
>different values for the height and width but nothing I've tried has 
>made it look better or worse.
>http://kylemulka.com/cgi-bin/mapserv?map=floorplans.map&REQUEST=GetMap&
>S 
>ERVICE=WMS&VERSION=1.1.1&LAYERS=dude-1&STYLES=&BGCOLOR=0xFFFFFF&TRANSPA
>R
>ENT=TRUE&SRS=EPSG:4326&BBOX=-83.7158203125,42.2905166207974,-83.7144470
>2
>148438,42.291532494305976&WIDTH=256&HEIGHT=256
>
>-Kyle
>
>Josh Livni wrote:
>  
>
>>Kyle,
>>
>>I could be wrong -- I haven't used a mapserver wms in Google Maps - 
>>but I think your mapserver image may be being squashed a bit.  It's a 
>>bit less wide relative to the height/width of your Imagemagick 
>>version. Also the gmap div seems to be a different height/width in the
>>    
>>
>
>  
>
>>different versions.
>>
>>WMS will happily respond with the exact extent, but perhaps not the 
>>relative height/width you expect, thus 'squashing' the image, which 
>>may be causing the image issues you're seeing.
>>
>>You may want to play with this by adding a &height &width to the wms 
>>query, or you could try playing with the div height/width ratios, and 
>>seeing if you get similar results if one is a bit off, as I may be 
>>off-base with this theory.
>>
>>  -Josh
>>
>>Kyle Mulka wrote:
>>
>>    
>>
>>>I have these very detailed floor plans that I'd like to georeference 
>>>and display through mapserver's WMS sever, however, the clarity of 
>>>the images degrades when it goes through. How can I increase the 
>>>clarity of these floorplans through the WMS?
>>>
>>>Here's with mapserver:
>>>http://maps.kylemulka.com/floorplan-test10.php
>>>
>>>Here's without (simply chopping up tiles using Imagemagick) 
>>>http://maps.kylemulka.com/imagemagick/livedude.php
>>>
>>>Here's the parts of the map file for just the first floor:
>>>MAP
>>>NAME "UofM"
>>>  FONTSET fontset.txt
>>>  PROJECTION
>>>      "init=epsg:4326"
>>>  END
>>>IMAGETYPE png24
>>>EXTENT  -83.747063 42.272038 -83.709126 42.297056 SHAPEPATH 
>>>"/umdata/"
>>>LAYER
>>>  NAME "dude-1"
>>>  TYPE raster
>>>  DATA "dude1.tif"
>>>  PROCESSING "RESAMPLE=AVERAGE"
>>>  PROCESSING "DITHER=YES"
>>>    METADATA
>>>      "wms_title" "dude-1"
>>>      "wms_onlineresource" 
>>>"http://kylemulka.com/cgi-bin/mapserv?map=floorplans.map&"
>>>      "wms_srs" "EPSG:4326"
>>>  END
>>>  STATUS ON
>>>END
>>>END
>>>
>>>-Kyle
>>>      
>>>
>>
>>
>>
>>    
>>
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