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geo-assign any arbitrary image to a geotiff usable in tilemill
import subprocess
import sys, re
MERC = '+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs'
infile = sys.argv[1]
info_output = subprocess.Popen(['gdalinfo', infile], stdout=subprocess.PIPE).communicate()[0]
size_is_re = re.compile('Size is (?P<width>\d+), (?P<height>\d+)')
size_is = filter(lambda x: x, map(lambda x: size_is_re.match(x), info_output.split('\n')))
if (len(size_is) != 1):
raise 'Could not parse gdalinfo output for image size'
size = [float(size_is[0].group('width')), float(size_is[0].group('height'))]
aspect_ratio = size[1] / size[0]
# the full world dimension
dim = 20037508.34 * 2
if (aspect_ratio > 1):
h = dim
w = dim / aspect_ratio
else:
h = dim * aspect_ratio
w = dim
res = subprocess.call(['gdal_translate', '-a_ullr', str(-w/2), str(-h/2), str(w/2), str(h/2), '-a_srs', MERC, infile, '%s.tif' % infile])
if res != 0:
raise 'An error occurred upon calling gdal_translate'
@timoha

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timoha commented Apr 19, 2013

I'm having an issue with importing generated tif into QGIS. Once I add it as a waster layer, the image appears upside down. Is it something I have to configure in QGIS or modify your script. Thanks!

@timoha

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timoha commented Apr 22, 2013

Should be

['gdal_translate', '-a_ullr', str(-w/2), str(h/2), str(w/2), str(-h/2), '-a_srs', MERC, infile, '%s.tif' % infile]

This way the corner coordinates are correct

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