Create PNG from Shapefile

gistfile1.py

import shapefile
import pngcanvas

# Open shapefile with Python Shapefile Library
shapefile_name = 'REPLACE_WITH_SHAPEFILE_NAME' # e.g. england_oa_2001
r = shapefile.Reader(shapefile_name)

# Determine bounding box x and y distances and then calculate an xyratio
# that can be used to determine the size of the generated PNG file. A xyratio
# of greater than one means that PNG is to be a landscape type image whereas
# an xyratio of less than one means the PNG is to be a portrait type image.
xdist = r.bbox[2] - r.bbox[0]
ydist = r.bbox[3] - r.bbox[1]
xyratio = xdist/ydist
image_max_dimension = 600 # Change this to desired max dimension of generated PNG
if (xyratio >= 1):
    iwidth  = image_max_dimension
    iheight = int(image_max_dimension/xyratio)
else:
    iwidth  = int(image_max_dimension/xyratio)
    iheight = image_max_dimension

# Iterate through all the shapes within the shapefile and draw polyline
# representations of them onto the PNGCanvas before saving the resultant canvas
# as a PNG file
xratio = iwidth/xdist
yratio = iheight/ydist
pixels = []
c = pngcanvas.PNGCanvas(iwidth,iheight)
for shape in r.shapes():
    for x,y in shape.points:
        px = int(iwidth - ((r.bbox[2] - x) * xratio))
        py = int((r.bbox[3] - y) * yratio)
        pixels.append([px,py])
    c.polyline(pixels)
    pixels = []
f = file("%s.png" % shapefile_name,"wb")
f.write(c.dump())
f.close()

# Create a world file
wld = file("%s.pgw" % shapefile_name, "w")
wld.write("%s\n" % (xdist/iwidth))
wld.write("0.0\n")
wld.write("0.0\n")
wld.write("-%s\n" % (ydist/iheight))
wld.write("%s\n" % r.bbox[0])
wld.write("%s\n" % r.bbox[3])
wld.close

Hi, 9 years later....
Line 20 should be multiplying by the xyratio.
Explanation:
If xyratio < 1, the width is smaller than the height. Dividing by a number < 1 will make the width larger, rather than smaller, as we intent.

Otherwise, thanks for this. Saved me a few hours and got me introduced to the meat of shapefiles.