Add a template filter for displaying signature as base64

jsignature/templatetags/jsignature_filters.py

@@ -0,0 +1,21 @@
+import base64
+import io
+
+from django import template
+from django.utils.encoding import iri_to_uri
+
+from jsignature.utils import draw_signature
+
+register = template.Library()
+
+
+@register.filter
+def signature_base64(value):
+    if value is None or not isinstance(value, str):
+        return ""
+    in_mem_file = io.BytesIO()
+    draw_signature(value).save(in_mem_file, format="PNG")
+    in_mem_file.seek(0)
+    return "data:image/png;base64,{}".format(
+        iri_to_uri(base64.b64encode(in_mem_file.read()).decode('utf8'))
+    )