Refactored command-line interface

CLI now based on Python argparse conventions.

README.md

@@ -15,14 +15,14 @@ $ ./gdal_extent.py Wayne_county.tiff
 To get the width/height of a raster:
 
 ```sh
-$ ./gdal_extent.py -size Wayne_county.tiff
+$ ./gdal_extent.py --size Wayne_county.tiff
 1875 1551
 ```
 
 To get a GeoJSON Polygon for the rectangular extent as a string, with 2 spaces for indentation:
 
 ```sh
-$ ./gdal_extent.py -geojson -i 2 Wayne_county.tiff
+$ ./gdal_extent.py --extent --as-json -i 2 Wayne_county.tiff
 {
   "coordinates": [
     [

gdal_extent.py

@@ -3,11 +3,24 @@
 # A command-line utility for getting the extent (bounds) of any raster as
 # Well-Known Text (WKT), GeoJSON, or other vector formats.
 
+import argparse
 import json
 import sys
 from osgeo import gdal, ogr
 
-def get_min_max_extent(rast):
+class CustomArgumentParser(argparse.ArgumentParser):
+    def error(self, message):
+        # Default with no options/ switches: Report min/max bounds
+        if message.find('unrecognized arguments') >= 0:
+            main(sys.argv[1:], get_min_max_bounds)
+            sys.exit(2)
+
+        sys.stderr.write('error: %s\n' % message)
+        self.print_help()
+        sys.exit(2)
+
+
+def get_min_max_bounds(rast):
     '''
     Returns the minimum and maximum coordinate values in the sequence expected
     by, e.g., the `-te` switch in various GDAL utiltiies:
@@ -21,7 +34,7 @@ def get_min_max_extent(rast):
     return [gt[0], gt[3] - (ysize * yr), gt[0] + (xsize * xr), gt[3]]
 
 
-def get_rect_extent_as_geojson(rast, as_string=False):
+def get_rect_extent(rast):
     '''
     Returns the rectangular extent as GeoJSON Polygon string.
     '''
@@ -30,16 +43,11 @@ def get_rect_extent_as_geojson(rast, as_string=False):
     # Repeat the last coordinate (for closure)
     ext.append(ext[0])
 
-    result = {
+    return {
         'coordinates': [ext],
         'type': 'Polygon'
     }
 
-    if as_string:
-        return json.dumps(result, sort_keys=False, indent=2)
-
-    return result
-
 
 def get_rect_extent_as_sequence(rast):
     '''
@@ -48,7 +56,7 @@ def get_rect_extent_as_sequence(rast):
     and moving clockwise.
     '''
     gt = rast.GetGeoTransform()
-    c = get_min_max_extent(rast)
+    c = get_min_max_bounds(rast)
     # Top-left, top-right, bottom-right, bottom-left
     return [(c[0], c[3]), (c[2], c[3]), (c[2], c[1]), (c[0], c[1])]
 
@@ -64,65 +72,63 @@ def stringify(sequence, sep=' '):
     return ' '.join(map(str, sequence))
 
 
-def display_usage():
-    print('Usage: gdal_extent.py [-geojson|-size] [-i indentation] input_files')
-    print('')
-
-
-def main(argv=None):
-    if argv is None:
-        argv = sys.argv
-
-    argv = gdal.GeneralCmdLineProcessor(argv)
-    func = get_min_max_extent # Function to call
-    indent = None # Indentation level
-    json_out = False # Output is JSON
-    names = [] # Filenames found
-
-    if argv is None:
-        sys.exit(0)
-
-    # Parse command line arguments.
-    i = 1
-    while i < len(argv):
-
-        if argv[i] == '-i':
-            indent = int(argv[i + 1])
-            i += 1
-
-        elif argv[i] == '-geojson':
-            json_out = True
-            func = get_rect_extent_as_geojson
-
-        elif argv[i] == '-size':
-            func = get_width_height
-
-        else:
-            names.append(argv[i])
-
-        i += 1
-
-    if len(names) == 0:
-        sys.stdout.write('No input files selected.')
-        display_usage()
-        sys.exit(1)
-
+def main(args, handler, as_json=False, indent=None):
     # Execute the function for each filename
-    for name in names:
+    for name in args:
         ds = gdal.Open(name)
 
-        if json_out:
-            sys.stdout.write(json.dumps(func(ds), sort_keys=False,
+        # Write results to standard output
+        if as_json:
+            sys.stdout.write(json.dumps(handler(ds), sort_keys=False,
                 indent=indent))
 
         else:
-            sys.stdout.write(stringify(func(ds)))
+            sys.stdout.write(stringify(handler(ds)))
 
         sys.stdout.write('\n')
         ds = None
 
-    return 0
-
 
 if __name__ == '__main__':
-    sys.exit(main())
+    parser = CustomArgumentParser(description='''
+        A command-line tool for reporting the extent of GDAL datasets:
+        [-b --bounds] returns the min-max bounds (xmin, ymin, xmax, ymax);
+        [-e --extent] returns the rectangular extent as a GeoJSON polygon;
+        [-s --size]   returns the width and height.
+    ''')
+
+    # Commands
+    commands_group = parser.add_mutually_exclusive_group()
+    commands_group.add_argument('-b', '--bounds', metavar='PATH',
+        nargs='*', help='')
+    commands_group.add_argument('-e', '--extent', metavar='PATH',
+        nargs='*', help='')
+    commands_group.add_argument('-s', '--size', metavar='PATH',
+        nargs='*', help='')
+
+    # Options
+    parser.add_argument('-j', '--as-json', action='store_true',
+        help='output GeoJSON')
+    parser.add_argument('-i', '--indent', metavar='WIDTH', default=None,
+        help='indentation for output GeoJSON', type=int)
+
+    # If no arguments are supplied...
+    if len(sys.argv) == 1:
+        parser.print_usage()
+        sys.exit(1)
+
+    args = parser.parse_args()
+    kwargs = {
+        'as_json': args.as_json,
+        'indent': args.indent
+    }
+
+    if args.bounds:
+        main(args.bounds, get_min_max_bounds, **kwargs)
+
+    elif args.extent:
+        kwargs['as_json'] = True # Force JSON output
+        main(args.extent, get_rect_extent, **kwargs)
+
+    elif args.size:
+        main(args.size, get_width_height, **kwargs)