Zhonghai,
My
guess is that both the gdal_warp and gdal_merge utilities use the pusedo colour
table of the first image and apply that table to all other images, I would try
converting the gif to RGB geotiffs using the pct2rgb gdal utility then go
through your processing steps(warping and merging) then convert the
images back to 8bit GIFs. I hope this helps
Travis
-----Original Message-----
From: UMN MapServer Users List [mailto:[EMAIL PROTECTED]On Behalf Of Zhonghai Wang
Sent: Tuesday, June 06, 2006 6:35 AM
To: [email protected]
Subject: [UMN_MAPSERVER-USERS] raster image preprocessing problem.Hi there,I have a couple of GIFs with wld files, but the original Projection is not the one I want, I tried to use the Proj4 to reproject them on-the-fly, but it takes really long to perform the map request, therefore I tried to preprocess the images with GDAL tools, but I've got some problems here:1. problem with gdalwarp: trying to mosaic the images into one output file, but only the first image has the correct image color, the other images are rendered with strange colors, is this a common problem if using gdalwarp to mosaic images?2.problem with gdal_merge.py: after trying the gdalwarp command, I've tried the gdal_merge.py command to merge all the images together with the -pct parameter, unfortunately, the merged image is the same as the first try. is it possible to merge images using the command with the correct color table?BTW: I can not use the gdal_translate command, since there are gaps between the reprojected images.thanks for your info.zhonghai
