LatitudePlot.py

#!/usr/bin/env python

# LatitudePlot.py
# Created 30 July 2013
# Created by snowdonjames@googlemail.com

import os, time, math
from datetime import datetime
from time import mktime
import xml.etree.ElementTree as ET
from PIL import Image, ImageDraw

def GetKmlFiles():
    """Locates and reads local .kml files, returns a list of kml dictionary data""" 
    KmlData = []
    for dirname, dirnames, filenames in os.walk('.'):
        for filename in filenames:
            sp = filename.split('.')
            if  sp[len(sp)-1]== "kml": #locate kml files
                print "Reading kml file " + filename
                KmlData.append(ReadKmlFile(dirname, filename))
    return KmlData

def ReadKmlFile(dirname, filename):
    """Parses a single kml file, returns a dict of format {time: [lat, long]}"""
    KmlData = {}
    kmltime = datetime.time
    latlist = []
    longlist = []
    timelist = []
    cnt =0
    f = open(filename)
    line = f.readline()
    while line:
        if 'when' in line:
            timelist.append(time.strptime(ET.fromstring(line)[0].text,"%Y-%m-%dT%H:%M:%SZ"))
        if 'coordinates' in line:
            latlist.append(float(ET.fromstring(line)[0].text.split(',')[0]))
            longlist.append(float(ET.fromstring(line)[0].text.split(',')[1]))
            cnt+=1
            if cnt % 5000 ==0:
                print "Parsing " + filename + ": points found: " + str(cnt)
        line = f.readline()
    f.close()
    return [latlist, longlist, timelist]

def DrawMapData(KmlData,InputImage, OutputImage, itop, ibottom, ileft, iright,xnudge,ynudge):
    """Draws kml line data on top of the specified image"""
    im = Image.open(InputImage)
    draw = ImageDraw.Draw(im)
    cnt =0
    for KmlD in KmlData:
        for d in range(len(KmlD[0])-1):
            #Get points x and y coordinates and draw line
            x1=(LongToX(KmlD[0][d],ileft,iright,im.size[0]))+xnudge
            y1=(LatToY(KmlD[1][d],itop,ibottom,im.size[1]))+ynudge
            x2=(LongToX(KmlD[0][d+1],ileft,iright,im.size[0]))+xnudge
            y2=(LatToY(KmlD[1][d+1],itop,ibottom,im.size[1]))+ynudge
            if(EuclidDistance(x1,y1,x2,y2) < 10000):
                #setting this around 80 works okay. Attempts to remove some noise  
                draw.line((x1,y1, x2,y2), fill=255)
            cnt+=1
            if cnt % 10000 ==0:
                print "Drawing point number " + str(cnt)
    im.save(OutputImage)
        
def LongToX(InputLong, LeftLong, RightLong, ImWidth):
    """Converts a longitude value in to an x coordinate"""
    return ScalingFunc(InputLong+360, LeftLong+360, RightLong+360, ImWidth);

def LatToY(InputLat, TopLat, BottomLat, ImHeight):
    """Converts a latitude value in to a y coordinate"""
    return ScalingFunc(InputLat+360, TopLat+360, BottomLat+360, ImHeight);

def EuclidDistance(x1, y1, x2, y2):
    """Calculates the euclidean distance between two points"""
    return math.sqrt((x1 - x2)**2+(y1 - y2)**2)

def ScalingFunc(inputv, minv, maxv, size):
    """Helps convert latitudes and longitudes to x and y"""
    if((float(maxv) -float(minv)) ==0):
       return 0
    return ((((float(inputv) - float(minv)) / (float(maxv) -float(minv))) * float(size)));

def ParseImageFile():
    """Reads SatelliteImageData.csv containing:
    <File name of image to draw data on>,
    <image top latitude>,
    <image bottom lattitude>,
    <image left longitude>,
    <image right longitude>,
    (optional) <x value nudge>,
    (optional) <y value nudge>"""
    with open('ImageData.csv', 'r') as f:
        read_data = f.read().split(',')
    while 5 <= len(read_data) < 7:
        read_data.append(0)
    ReturnData = [0]*7
    ReturnData[0]=read_data[0]
    for i in range(1,7):
        ReturnData[i] = float(read_data[i])
    return ReturnData

if __name__ == "__main__":
    ImageData = ParseImageFile()
    DrawMapData(GetKmlFiles(),ImageData[0], "LatitudeData.png", ImageData[1], ImageData[2], ImageData[3], ImageData[4],ImageData[5],ImageData[6])