adding parameter for no data value used in merge alg

merge_rename_bands_algorithm.py

@@ -34,6 +34,7 @@ from qgis.PyQt.QtCore import QCoreApplication
 from qgis.core import (QgsProcessingAlgorithm,
                        QgsProject,
                        QgsProcessingParameterDefinition,
+                       QgsProcessingParameterNumber,
                        QgsProcessingParameterRasterDestination)
 import processing
 from osgeo import gdal
@@ -79,6 +80,7 @@ class MergeAndRenameAlgorithm(QgsProcessingAlgorithm):
     # calling from the QGIS console.
 
     INPUT = 'INPUT'
+    NODATA = 'NODATA'
     OUTPUT = 'OUTPUT'
 
     def initAlgorithm(self, config):
@@ -95,6 +97,17 @@ class MergeAndRenameAlgorithm(QgsProcessingAlgorithm):
                 False # True if optional
             )
         )
+        
+        # parameter for no data value
+        self.addParameter(
+            QgsProcessingParameterNumber(
+                    self.NODATA,
+                    self.tr('No data value'), 
+                    type=QgsProcessingParameterNumber.Integer, 
+                    defaultValue=0,
+                    optional=True
+            )
+        )
             
         # output raster layer
         self.addParameter(
@@ -112,6 +125,7 @@ class MergeAndRenameAlgorithm(QgsProcessingAlgorithm):
 
         # RETRIEVE INPUTS AND OUTPUT
         input_param = ParameterMergeBandTable.tableValuesAsList(parameters[self.INPUT])
+        nodata = self.parameterAsDouble(parameters, self.NODATA, context)
         output_raster_path = self.parameterAsOutputLayer(parameters, self.OUTPUT, context)
         
         # GETTING USEFUL PARAMETERS
@@ -136,6 +150,7 @@ class MergeAndRenameAlgorithm(QgsProcessingAlgorithm):
         merge_param = {
                 'INPUT' : rasterPaths,
                 'SEPARATE' : True,
+                'NODATA_OUTPUT' : nodata,
                 'OUTPUT' : output_raster_path
                 }
         processing.run("gdal:merge", merge_param, context=context, feedback=feedback)