Add support for reading PNG files [MPY-397]

iainrussell · iainrussell · commit 0c3230b15820 · 2023-09-22T09:50:41.000Z
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
@@ -3,6 +3,11 @@ Changelog for Metview's Python interface
 
 ========================================
 
+1.16.0 (unreleased)
+-------------------
+- Added support for reading PNG files
+
+
 1.15.0
 ------------------
 - Added arguments() function to mimic the behaviour of the Macro function of the same name
diff --git a/metview/bindings.py b/metview/bindings.py
@@ -1218,9 +1218,17 @@ def translate_return_val(self, val):
         try:
             return self.funcs[rt](val)
         except Exception:
-            raise Exception(
-                "value_from_metview got an unhandled return type: " + str(rt)
-            )
+            # if the type is unknown, it might be a type that is actually stored
+            # as a request rather than as a MARS type, e.g. PNG
+            try:
+                if rt == 99:
+                    rt = MvRetVal.trequest.value
+                    return self.funcs[rt](val)
+            except Exception:
+                raise Exception(
+                    "value_from_metview got an unhandled return type and could not convert to a Request: "
+                    + str(rt)
+                )
 
 
 vr = ValueReturner()
diff --git a/tests/test_metview.py b/tests/test_metview.py
@@ -216,6 +216,11 @@ def test_modify_embedded_request_via_update():
     # mv.plot(a, gv)
 
 
+def test_read_png():
+    p = mv.read(file_in_testdir("MVPROFILEVIEW.png"))
+    assert p.get_verb() == "PNG"
+
+
 def test_print():
     mv.print("Start ", 7, 1, 3, " Finished!")
     mv.print(6, 2, " Middle ", 6)
