<html><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><META name="Author" content="Novell GroupWise WebAccess"></head><body style='font-family: Tahoma, sans-serif; font-size: 13px; '>
Hello<br><br>I have a problem with MapServer making a mess of some georegistered raster map images when serving them as tiles via WMS. The images are not reprojected on the fly, so this isn't the cause of the problem. The source images are 24bit geotiff and the requesting format is jpeg or png.<br><br>The maps are OS New Popular and they exhibited poor contrast so I boosted the contrast and colours in Photoshop 7 using the auto color or the auto contrast option. Unfortunately, some of the sheets now exhibit horrible artefacting or ghost images. Other maps in the set that have been boosted do not have these problems. I attach two screenshots, original.jpg and mapserver.jpg. These are portions of the original image and the MapServer served image, respectively. Further examples of this problem can be found via the map viewer on Historical Maps section of the Vision of Britain website (www.visionofbritain.org.uk), check out the New Popular maps in the vicinity of the Wirral.<br><br>I have tried various things to fix this, but to no avail. Things I have tried:<br><br>Increasing the jpeg quality output<br>Using png instead of jpeg for the output<br>Using GDAL or AGG instead of GD<br><br>Here is the output format portion of my map file:<br><br>OUTPUTFORMAT<br> NAME "jpg"<br> DRIVER GD/JPEG<br> IMAGEMODE RGB<br> EXTENSION "jpg"<br> MIMETYPE "image/jpg"<br> FORMATOPTION "QUALITY=85"<br>END<br><br>OUTPUTFORMAT<br> NAME "png"<br> DRIVER GD/PNG<br> IMAGEMODE RGB<br> EXTENSION "png"<br> MIMETYPE "image/png"<br>END<br><br>Does anybody have any ideas what the problem could be? I know it is something to do with the fact that I boosted the images and MapServer doesn't like them, but I would like to fix it. Suggestions greatly appreciated.<br><br>Regards,<br><br>John Westwood<br><br>Great Britain GIS Project<br>Vision of Britain<br>www.visionofbritain.org.uk<br></body></html>