By default, gdal_merge.py starts by creating an output image with all black 
pixels, and then replaces these black pixels with pixels from the images being 
read in. Passing to gdal_merge.py -init 255 pre-initializes the output image to 
all white, instead of all black, pixels.
Similar to gdal_merge.py, gdalbuildvrt fills with black pixels. I am seeking 
for gdalbuildvrt, the -init 255 option that gdal_merge.py supports, but do not 
see -init 255 as a supported option on the gdalbuildvrt man page. In GDAL 
1.7.0, will gdalbuildvrt support -init 255? If not, then in GAL 1.7.0 can the 
option -vrtnodata be used in a way similar to how gdal_merge.py supports -init 
255? I need areas where there is no image to be white, rather than the black 
that gdalbuildvrt is by default setting them to be.
Greg

gdal_merge.py man page
http://www.gdal.org/gdal_merge.html
gdalbuildvrt man page
http://www.gdal.org/gdalbuildvrt.html
gdalbuild_black image
http://homepage.mac.com/gregcoats/jp2/images/gdalbuildvrt_black.png
gdalbuildvrt_white image (simulated)
http://homepage.mac.com/gregcoats/jp2/images/gdalbuildvrt_white.png

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