Python GDAL RasterizeLayer option parameter

Question

I'm writing some code that's supposed to take multiple multipolygon layers and merge them into 1 raster. I can load in the datasets just fine and render them to an image (although I use this just for debugging), here's what I'm doing right now:

noiselayers["noise"] = [[1, 0.1], [2, 0.8]]

    #create a source in memory
    ds = ogr.GetDriverByName("Memory").CreateDataSource("wrk")
    source = ds.CreateLayer("", None, ogr.wkbMultiPolygon )
    source.CreateField(ogr.FieldDefn("VAL", ogr.OFSTFloat32))

    for layerdata in noiselayers[selected]:
        data = requests.get("http://localhost/api/layer/export/%s" % str(layerdata[0]))
        geometry = json.loads(data.text)

        for g in geometry:
            geom = ogr.CreateGeometryFromWkt(g['the_geom'])

            structure = ogr.Feature(source.GetLayerDefn())
            structure.SetGeometry(geom)
            structure.SetField("VAL", layerdata[1])

            #save geometry to layer
            source.CreateFeature(structure)


    pixelsize = 1000
    #novalue = -9999

    #get the layer bounds dynamically from the layer        
    #x_min, x_max, y_min, y_max = layer.GetExtent()

    #extracted values from ns_play_area_final_EPSG_3035
    x_min = 2777236.78057
    x_max = 5065039.36824
    y_min = 2815620.0976
    y_max = 4485652.62185

    x_res = int((x_max - x_min) / pixelsize)
    y_res = int((y_max - y_min) / pixelsize)

    target = gdal.GetDriverByName("MEM").Create("", x_res, y_res, 1, gdal.GDT_Byte)
    target.SetGeoTransform((x_min, pixelsize, 0, y_max, 0, -pixelsize))            

    gdal.RasterizeLayer(target, [1], source)

This grabs a bunch of data from our API and rasterizes it just fine. However, I need to merge multiple layers with different weights (in the noiselayers variable, the 2nd value of each list is the weight). When it's a higher value it should increase the value more, for now just setting the value of the square to that value is enough. I've tried using the options (as seen here: https://svn.osgeo.org/gdal/trunk/autotest/alg/rasterize.py), but they never seem to do anything, here's some of the things I tried to use the options:

gdal.RasterizeLayer(target, [1], source, None, None, [1000], ["ATTRIBUTE=VAL"])

gdal.RasterizeLayer(target, [1], source, options = ["ATTRIBUTE=VAL"])

• any combination of the 2, the options never seem to do anything other than break the rasterizing. I've also tried inversing (using INVERSE=TRUE, or any combination of capitalizing/not capitalizing that) the raster, but that also never seemed to work.

Does anyone have a working example of how to use attributes and/or other hints on how to solve my issue?

Answer 1

Those options never worked for me either. I ended up using a work around by setting attribute filters on the layer object. How about this:

for index, weight in noiselayers[selected]:
    source.SetAttributeFilter('VAL={}'.format(weight))
    gdal.RasterizeLayer(target, [1], source, burn_values=[weight])

# reset the filter
source.SetAttributeFilter('')

you can find the attribute filter documentation here.