merge_and_warp.py

#Definition of inputs and outputs
#==================================
##Budyko=group
##Merge, reproject and subset=name
##ParameterMultipleInput|inputImages|Input images|3|
##ParameterCrs|projection|Metric coordinate system (UTM)|
##ParameterExtent|extent|Spatial extent|
##ParameterCrs|extentProjection|Coordinate system of the extent|EPSG:4326|False
##ParameterNumber|resolution|Spatial resolution in target coordinate system (leave as 0 for no change)|0.0|100000000.0|0.0|
##OutputRaster|outputImage|Output image

# This script is not made as a model because there is no ParameterMultipleInput in the QGIS 2.x 
# modeler (it exists in QGIS 3.x)

# Run Build Virtual Raster to merge the images
params = {'INPUT': inputImages, 'RESOLUTION': "0", 'SEPARATE': False, 
          'PROJ_DIFFERENCE': False, 'OUTPUT': None}
vrtOutput = processing.runalg("gdalogr:buildvirtualraster", params)

# Run GDAL warp to reproject, resample and subset
params = {'INPUT': vrtOutput['OUTPUT'], 'DEST_SRS': projection, 'METHOD': 5, "TR": resolution,
          'USE_RASTER_EXTENT': True, 'RASTER_EXTENT': extent, 'EXTENT_CRS': extentProjection, 
          'NO_DATA': "-32768", "OUTPUT": outputImage}
processing.runalg("gdalogr:warpreproject", params)