Opened 17 years ago

Last modified 17 years ago

#1956 assigned defect

pixel shift

Reported by: jukka.sirvio@… Owned by: sdlime
Priority: high Milestone:
Component: MapServer CGI Version: 4.10
Severity: normal Keywords:
Cc: steven.ottens@…

Description

We are generating tiles for a uDig -based mapping application using 
MapServer's WMS connection. We simply give the extents of each image 
requested - extents are calculated so that we always gain images on size 1024 
x 1024 pixels. Extend coordinates in WMS query should be ok.

The issue is that lines are uncontinuos on the border of the tiles. If line 
crosses the tile border on the angle 45 - 90 degrees no problems appear. 
However, if the angle is between 0 - 45 degrees the line is broken. See 
attached image. On the image the yellow line respresents tile border and the 
red line represents trail. White pixels are the MapServer's raster 
intepretation of the red line. The problem is that the "trail" line is broken 
(uncontinuous) on the border of tile.

Attachments (1)

broken_border.jpg (27.8 KB ) - added by jukka.sirvio@… 17 years ago.
Here is the picture from the problem

Download all attachments as: .zip

Change History (9)

by jukka.sirvio@…, 17 years ago

Attachment: broken_border.jpg added

Here is the picture from the problem

comment:1 by jukka.sirvio@…, 17 years ago

I am able to provide reproducable testcase from this (size about 20mb). 

Testcase contains:
1) ecw raster image
2) line type shp vector layer 
3) mapfile (must be edited with correct paths)
4) wms urls (must be edited with correct paths)

Give me an email if someone is interested about this 
(jukka.sirvio@arbonaut.com)!

comment:2 by fwarmerdam, 17 years ago

Bug 1957 may also be related.  

comment:3 by jukka.sirvio@…, 17 years ago

dependson: 1957
Status: newassigned

comment:4 by jukka.sirvio@…, 17 years ago

testcase can be downloaded from following address (at least a week):

address: 194.197.204.10
username: steve
password: steveli 

comment:5 by jukka.sirvio@…, 17 years ago

Cc: steven.ottens@… added

comment:6 by jukka.sirvio@…, 17 years ago

Cc: dmorissette@… added

comment:7 by jukka.sirvio@…, 17 years ago

Cc: warmerdam@… added

comment:8 by sdlime, 17 years ago

Jukka: Can you try the CVS version of GD (www.libgd.org) and see if that helps?

Steve
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