Jonathan Moules <jonathanmoules <at> warwickshire.gov.uk> writes:
> > > Hi Jukka,Good point. In fact, that's one of the reasons I want to set the noData flag. I figure when compressing hopefully the compressor will see that it is "noData" and will treat it differently from the way it would an actual value (which results in things like your mentioned 255,255,254) so I won't get the white-border-effect. I guess I'll find out if/when I get to that point. Hi, As far as I know GDAL does not do miracles. You cannot make a perfect result with rotated images, noData value and jpeg compression if you warp first and mosaic afterwards. If you want to use jpeg compression, as I suppose you do, turn the order and mosaic first - warp next. Build a virtual mosaic when you still play in the world of the native projection and warp images to target projection by using –projwin. That way at least the images from the middle parts of your site will be rectangular and without noData areas at all in the target srs and you will have no issues with jpeg compression. You will still get non-transparent pixels into the borders of your site but you can create those images without compression or with lossless LZW/deflate compression. You are anyways so well oriented in doing controlled tests that you will probably do little experiments with your own data and mosaics of size 2x2 or 3x3 tiles before running huge batches. However, if your originals don't have white borders of noData areas withing the image area then you will not have them either after running your commands. gdalbuildvrt -hidenodata -srcnodata 255 -vrtnodata 255 -input_file_list tiff_list.txt 255.vrt gdal_translate -of GTiff -co TILED=YES -co BIGTIFF=YES -co COMPRESS=JPEG -co JPEG_QUALITY=80 -co BLOCKXSIZE=512 -co BLOCKYSIZE=512 -co PHOTOMETRIC=YCBCR 255.vrt 255mask.tif In this case using noData is not necessary either and may actually burn holes into your images if there are some extremely light areas of dry, plain terrain or the sun is reflecting from the water bodies and roofs of the buildings etc. -Jukka- _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
