I will look into the vet file. I often have multiple input files and didn't see a way to use the cutline option with multiple input cutline. On Nov 25, 2013 3:33 PM, "Even Rouault" <[email protected]> wrote:
> Le lundi 25 novembre 2013 22:29:00, Simon Shak a écrit : > > I’m working with gdalwarp to reprocess a large amount of imagery to be > > compatible with another program that requires imagery to be in WGS84. > The > > input imagery is compressed in MrSID format and does not include an > > internal mask for nodata. I don’t know if this is because the creator of > > the imagery overlooked it, or if the format doesn’t support a mask. > Either > > way, when I attempt to merge neighboring sets, I get odd bands of dark > > color. I’ve looked closely, and it is evident because at the edge of the > > images are non 100% black pixels, that though I’m sending –srcnodata 0 > into > > gdalwarp, they get read as pixels and progress through. I’ve looked into > > using the nearblack command on the files first, but the compression ratio > > of the .SID files makes it such that the files don’t easily fit into my > > hard drive array for pre-nearblacking them before processing, plus the > > physical size of some of these files are large enough that the nearblack > > takes a long time to run. Without the nearblack step, my multithreaded > > control script can process one chunk in a day, but adding the nearblack, > > and it increases to a week at least. > > > > > > > > I’m looking for a solution that would not require making a large interim > > uncompressed version and would hopefully not incur a lengthy additional > > process. > > > > > > > > The simpler thoughts I have would be to adjust gdalwarp’s –srcnodata to > > take a range option, much like nearblack, so that if it detects a pixel > > (even in the middle) that is with the range specified would get ignored, > or > > a way to include an ancillary file that could contain a mask. Either > would > > work for me, I have potential ways to quickly generate a mask for the > input > > files. I’d think the mask could work much like .TIF can have a .TFW, > that > > a .MSK could be detected as well. > > You can use the -cutline option of gdalwarp if you have the mask as a > shapefile > or another OGR datasource. > You could also use a VRT file to combine the MrSID imagery and add another > band > from TIF for example as the alpha/mask band. > > > -- > Geospatial professional services > http://even.rouault.free.fr/services.html >
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