New class with code extracted from bandraster, for more general use

formats/auxiliaryfile.py

+from xml.dom import minidom
+import os.path
+from math import floor
+import traceback
+ 
+__author__ = "Steven B. Hoek"
+
+class AuxiliaryFile(object):
+    """A helper class that can handle the common *.aux.xml files used by ArcGIS and GDAL"""
+    datafile = None
+        
+    def __enter__(self):
+        return self
+    
+    def __exit__(self, exc_type, exc_value, tb):
+        try:
+            if exc_type is not None:
+                traceback.print_exception(exc_type, exc_value, tb)
+                return False
+            else:
+                return True
+        finally:
+            if self.datafile is not None: self.datafile.close()            
+        
+    def __getpath(self, aRaster):
+        result = os.path.join(aRaster.folder, aRaster.name) + ".aux.xml"
+        return result
+    
+    def read(self, aRaster):
+        result = -9999
+        pathtoxml = self.__getpath(aRaster)
+        if os.path.exists(pathtoxml):
+            # Assume there is only a single band
+            doc = minidom.parse(pathtoxml)
+            nodatatag = doc.getElementsByTagName("NoDataValue")
+            tmpstr = nodatatag[0].firstChild.nodeValue
+            if tmpstr.find('.') != -1: result = floor(float(tmpstr))
+            else: result = int(tmpstr)
+        return result
+    
+    def write(self, aRaster):
+        pathtoxml = self.__getpath(aRaster)        
+        if not os.path.exists(pathtoxml):
+            xmldoc = minidom.Document()               
+            root = xmldoc.createElement('PAMDataset')  
+            xmldoc.appendChild(root)               
+            bandChild = xmldoc.createElement('PAMRasterBand') 
+            bandChild.setAttribute('band', '1')               
+            root.appendChild(bandChild)     
+            nodataChild = xmldoc.createElement('NoDataValue') 
+            bandChild.appendChild(nodataChild)
+            textnode = xmldoc.createTextNode(str(aRaster.nodatavalue))
+            nodataChild.appendChild(textnode) 
+            xmltext = xmldoc.toprettyxml(indent ="  ")
+            with open(pathtoxml) as x:
+                x.write(xmltext)
+        else:
+            # Check if such a file already contains a NoDataValue node
+            dirty = False
+            with open(pathtoxml, 'r') as infile:
+                xmltext = "".join(infile.readlines())
+                xmltext = xmltext.replace("\n", "")
+            xmldoc = minidom.parseString(xmltext)
+            
+            nodatatags = xmldoc.getElementsByTagName("NoDataValue")
+            if len(nodatatags) != 0:
+                nodatatags[0].firstChild.nodeValue = aRaster.nodatavalue
+                dirty = True
+            else:
+                bandChildren = xmldoc.getElementsByTagName("PAMRasterBand")
+                if len(bandChildren) != 0:
+                    nodataChild = xmldoc.createElement('NoDataValue')             
+                    bandChildren[0].appendChild(nodataChild)
+                    textnode = xmldoc.createTextNode(str(aRaster.nodatavalue))
+                    nodataChild.appendChild(textnode) 
+                    dirty = True
+            if dirty: 
+                # Ensure pretty looking XML: no lines with only whitespace!
+                xmltext = xmldoc.toprettyxml(indent = "  ")
+                xmllist = [line for line in xmltext.splitlines() if line.strip() != ""]
+                xmltext = "\n".join(xmllist)
+                with open(pathtoxml, 'w') as outfile:
+                    outfile.writelines(xmltext)