Add energy expressed in keV

tomoscan/unitsystem/metricsystem.py

@@ -29,9 +29,50 @@ __date__ = "01/09/2016"
 
 from silx.utils.enum import Enum as _Enum
 
+# Constants
+_elementary_charge_coulomb = 1.602176634e-19
 
-_meter = 1.0
 
+_joule_si = 1.0
+class EnergySI(_Enum):
+    """Util enum for energy in SI units (Joules)"""
+    JOULE = _joule_si
+    ELEMCHARGE = _elementary_charge_coulomb
+    ELECTRONVOLT = _elementary_charge_coulomb
+
+    KILOELECTRONVOLT = _elementary_charge_coulomb * 1e3
+    KILOJOULE = 1e3 * _joule_si
+
+    @classmethod
+    def from_value(cls, value):
+        if isinstance(value, str):
+            return cls.from_str(value=value)
+        else:
+            _Enum.from_value(value=value)
+
+    @classmethod
+    def from_str(cls, value: str):
+        assert isinstance(value, str)
+        if value.lower() in ('e', 'qe'):
+            return EnergySI.ELEMCHARGE
+        elif value.lower() in ("j", "joule"):
+            return EnergySI.JOULE
+        elif value.lower() in ("kj", "kilojoule"):
+            return EnergySI.KILOJOULE
+        elif value.lower() in ("ev", "electronvolt"):
+            return EnergySI.ELECTRONVOLT
+        elif value.lower() in ("kev", "kiloelectronvolt"):
+            return EnergySI.KILOELECTRONVOLT
+        else:
+            raise ValueError("Cannot convert: %s" % value)
+
+
+# Default units:
+#  - lenght: meter (m)
+#  - energy: kilo Electronvolt (keV)
+_meter = 1.0
+_kev = 1.0
+_joule_kev = 1./EnergySI.KILOELECTRONVOLT.value
 
 class MetricSystem(_Enum):
     """Util enum to retrieve metric"""
@@ -42,6 +83,12 @@ class MetricSystem(_Enum):
     MICROMETER = _meter * 1e-6
     NANOMETER = _meter * 1e-9
 
+    KILOELECTRONVOLT = _kev
+    ELECTRONVOLT = _kev * 1e-3
+    JOULE = _kev / EnergySI.KILOELECTRONVOLT.value
+    KILOJOULE = _kev / EnergySI.KILOELECTRONVOLT.value * 1e3
+
+
     @classmethod
     def from_value(cls, value):
         if isinstance(value, str):
@@ -62,6 +109,14 @@ class MetricSystem(_Enum):
             return MetricSystem.MICROMETER
         elif value.lower() in ('nm', 'nanometer'):
             return MetricSystem.NANOMETER
+        elif value.lower() in ('kev', 'kiloelectronvolt'):
+            return MetricSystem.KILOELECTRONVOLT
+        elif value.lower() in ('ev', 'electronvolt'):
+            return MetricSystem.ELECTRONVOLT
+        elif value.lower() in ('j', 'joule'):
+            return MetricSystem.JOULE
+        elif value.lower() in ('kj', 'kilojoule'):
+            return MetricSystem.KILOJOULE
         else:
             raise ValueError("Cannot convert: %s" % value)