Reduced/Increased size polygons with Buffering GDAL/OGR

Question

In case somebody needs to do the buffering of geometries (using pure OGR).

I am trying to create reduced/extended polygons from an existing polygon using OGR in Python.

The abstract idea that I have is to use the "Buffering" function of OGR to achieve the goal that is dressed here and here (using GIS interfaces).

More precisely I want to create a buffer with negative/positive distance and based on that create a new polygon with borders drawn inward/outward.

For this I used Create Buffer from GDAL/OGR cookbook as the template with a small addition of importing SRS from the input polygon to the output(buffer) polygon.

I have been suggested to use SQLite dialect in order to achieve it. This means that there are certainly more options to get the same results.

Here is the code:

import os
import sys
from osgeo import ogr 
from osgeo import osr

def createBuffer(inputfn, outputBufferfn, bufferDist):
    inputds = ogr.Open(inputfn)
    inputlyr = inputds.GetLayer()

    shpdriver = ogr.GetDriverByName('ESRI Shapefile')
    if os.path.exists(outputBufferfn):
        shpdriver.DeleteDataSource(outputBufferfn)
    outputBufferds = shpdriver.CreateDataSource(outputBufferfn)
    # create the spatial reference system, WGS84
    #srs =  osr.SpatialReference()
    #srs.ImportFromEPSG(4326)
    srs = inputlyr.GetSpatialRef()
    bufferlyr = outputBufferds.CreateLayer(outputBufferfn,srs, 
    geom_type=ogr.wkbPolygon)
    featureDefn = bufferlyr.GetLayerDefn()

    for feature in inputlyr:
        ingeom = feature.GetGeometryRef()
        geomBuffer = ingeom.Buffer(bufferDist)

        outFeature = ogr.Feature(featureDefn)
        outFeature.SetGeometry(geomBuffer)
        bufferlyr.CreateFeature(outFeature)
        outFeature = None

def main(inputfn, outputBufferfn, bufferDist):
    createBuffer(inputfn, outputBufferfn, bufferDist)


if __name__ == "__main__":
    inputfn = 'polygon.shp'
    outputBufferfn = 'polygonBuffer.shp'
    bufferDist = -1.0

    main(inputfn, outputBufferfn, bufferDist)