Ticket #20419: map_filter.patch

django/template/defaultfilters.py

@@ -888 +888 @@
         return pformat(value)
     except Exception as e:
         return "Error in formatting: %s" % force_text(e, errors="replace")
+
+###################
+# MATH            #
+###################
+
+@register.filter("map")
+def map_filter(value, src_min, src_max, dst_min, dst_max):
+    """map the value from [src_min,src_max] range to [dst_min, dst_max]
+    range.
+
+    Modeled after the corresponding map() function available (for
+    example) in Processing http://processing.org/reference/map_.html
+    """
+    return dst_min + value * ( dst_max - dst_min) / ( src_max - src_min)
+

tests/defaultfilters/tests.py

@@ -656 +656 @@
         self.assertEqual(removetags(123, 'a'), '123')
         self.assertEqual(striptags(123), '123')
 
+    def test_map_filter(self):
+        self.assertAlmostEqual(map_filter(0, 0, 100, 0, 1000), 0)
+        self.assertAlmostEqual(map_filter(0, 0, 100, 1000, 0), 1000)
+        self.assertAlmostEqual(map_filter(0, 100, 0, 0, 1000), 1000)
+        self.assertAlmostEqual(map_filter(10, 0, 100, 0, 1000), 100)