code fragment from RP v1 IESLoader.py

iesloader.py

    def _loadIESProfile(self, name, filename):
        """ Internal method to load an ies profile. Adapted from
        https://gist.githubusercontent.com/AngryLoki/4364512/raw/ies2cycles.py """
        # self.debug("Loading ies profile", filename, "as",len(self.profileNames))

        profileMultiplier = 1.0

        # Open the IES file
        with open(filename, 'r', encoding="utf-8", errors="ignore") as handle:
            content = handle.read()
            content.encode('utf-8')

        # Extract and check version string
        versionString, content = content.split('\n', 1)
        versionString = versionString.strip()

        if versionString in self.IESVersionTable:
            version = self.IESVersionTable[versionString]
        else:
            self.warn("No supported IES version found:",versionString)
            version = None

        # Extract IES properties
        keywords = dict()
        while content and not content.startswith('TILT='):
            key, content = content.split('\n', 1)
            if key.startswith('['):
                endbracket = key.find(']')
                if endbracket != -1:
                    keywords[key[1:endbracket]] = key[endbracket + 1:].strip()

        # After all properties, the tile keyword should follow
        keyword, content = content.split('\n', 1)

        if not keyword.startswith('TILT'):
            self.warn("TILT keyword not found")
            return False

        # Strip data
        fileData = content.replace(',', ' ').split()

        # Property 0 is the amount of lamps
        numLamps = int(fileData[0])
        if numLamps != 1:
            self.warn("Only 1 lamp is supported,", numLamps, "found:",name)

        # Extract further properties
        lumensPerLamp = float(fileData[1])
        candelaMultiplier = float(fileData[2])
        numVerticalAngles = int(fileData[3])
        numHorizontalAngles = int(fileData[4])

        # Check if everything went right so far
        if not numVerticalAngles or not numHorizontalAngles:
            self.error("Error during property extract")
            return False

        # Extract further properties
        photometricType = int(fileData[5])
        unitType = int(fileData[6])

        # Determine the unit type, either feet or meters
        if unitType not in [1, 2]:
            self.warn("Unkown unity type:", unitType)

        # Extract data size
        width, length, height = map(float, fileData[7:10])
        ballastFactor = float(fileData[10])

        futureUse = float(fileData[11])
        if futureUse != 1.0:
            self.warn("Invalid future use field")

        inputWatts = float(fileData[12])

        # Extract the actual data
        verticalAngles = [float(s) for s in fileData[13:13 + numVerticalAngles]]
        horizontalAngles = [float(s) for s in fileData[13 + numVerticalAngles:
                                              13 + numVerticalAngles + numHorizontalAngles]]

        # Determine the vertical light cone type. There are 90 and 180 degree cone types.
        if verticalAngles[0] == 0 and verticalAngles[-1] == 90:
            lampConeType = 'TYPE90'
        elif verticalAngles[0] == 0 and verticalAngles[-1] == 180:
            lampConeType = 'TYPE180'
        else:
            self.warn("Unsupported angles: ", verticalAngles[0], "-", verticalAngles[-1])
            lampConeType = 'TYPE180'

        # Determine the horizontal light cone type
        if len(horizontalAngles) == 1 or abs(horizontalAngles[0] - horizontalAngles[-1]) == 360:
            lampHorizontalConeType = 'TYPE360'
        elif abs(horizontalAngles[0] - horizontalAngles[-1]) == 180:
            lampHorizontalConeType = 'TYPE180'
        elif abs(horizontalAngles[0] - horizontalAngles[-1]) == 90:
            lampHorizontalConeType = 'TYPE90'
        else:
            self.warn("Unsupported horizontal angles: ", horizontalAngles[0], "-", horizontalAngles[-1])
            lampHorizontalConeType = 'TYPE360'
            
        # Read the candela values
        offset = 13 + len(verticalAngles) + len(horizontalAngles)
        candelaIndex = len(verticalAngles) * len(horizontalAngles)
        candelaValues = [float(s) for s in fileData[offset:offset + candelaIndex]]

        # Convert the 1d candela array to 2d array
        candela2D = list(zip(*[iter(candelaValues)] * len(verticalAngles)))

        # Compute the fallof gradient
        lampGradientData = [x / verticalAngles[-1] for x in verticalAngles]
       
        # Compute the radial gradient
        radialGradientData = [sum(x) / len(x) for x in zip(*candela2D)]
        radialGradientDataMax = max(radialGradientData)
        
        # Normalize the radial gradient by dividing by the maximum value
        radialGradientData = [val / radialGradientDataMax for val in radialGradientData]

        # Finally register the profile
        self._storeIESProfile(name, radialGradientData, lampGradientData)
        return True