Automatically switch renderer to EPS

This makes `./run -o 840147413574.eps 840147413574` generate an EPS file instead of an SVG file.

beautiful_barcode/barcode.py

@@ -1,3 +1,5 @@
+import os.path
+
 from . import renderers
 
 
@@ -6,14 +8,14 @@ def to_modules(self) -> str:
         """ Convert the Barcode to modules (1 or 0) """
         raise NotImplementedError
 
-    def render(self, renderer='auto') -> bytes:
+    def render(self, renderer='auto', extension=None) -> bytes:
         """ Renders the barcode as a bytes object """
 
-        rend = renderers.make_renderer(renderer)
+        rend = renderers.make_renderer(renderer, extension=extension)
         self._paint(rend)
         return rend.to_bytes()
 
     def write(self, filename, renderer='auto'):
-        data = self.render(renderer=renderer)
+        data = self.render(renderer=renderer, extension=os.path.splitext(filename)[1])
         with open(filename, 'wb') as out_file:
             out_file.write(data)

beautiful_barcode/renderers.py

@@ -108,10 +108,15 @@ def text(self, characters, x, y, scale=1):
             x += _DIGIT_WIDTH[char] * scale
 
 
-def make_renderer(spec):
+def make_renderer(spec, extension=None):
     if isinstance(spec, SVGRenderer):
         return spec  # Already a renderer, great
-    klass = NAMED_RENDERERS.get(spec, spec)
+
+    if spec == 'auto' and extension == '.eps':
+        klass = InkscapeEPSRenderer
+    else:
+        klass = NAMED_RENDERERS.get(spec, spec)
+
     return klass()
 
 

test/test_renderer.py

@@ -0,0 +1,13 @@
+import unittest
+
+import tutils  # noqa
+from beautiful_barcode.renderers import make_renderer, InkscapeEPSRenderer
+
+
+class RendererTest(unittest.TestCase):
+    def test_auto_eps(self):
+        svg_renderer = make_renderer('auto', extension='.svg')
+        self.assertFalse(isinstance(svg_renderer, InkscapeEPSRenderer))  # actual result is implementation-defined
+
+        eps_renderer = make_renderer('auto', extension='.eps')
+        self.assertTrue(isinstance(eps_renderer, InkscapeEPSRenderer))