# Created by Leo from: C:\Python23\Tom\leo\pyro.leo

# << demmod declarations >>
import struct,string
import Image
# -- end -- << demmod declarations >>
# << demmod methods >>
class demdata:
    # << class demdata methods >> (1 of 2)
    def __init__(self):    
        self.tom = open('c:\\python23\demdata\W140N40.DEM','rb')
        #gif = open('c:\\python23\demdata\W140N40.GIF','rb')
        bmp = Image.open('c:\\python23\demdata\W140N40.GIF').convert('RGB')
        self.imgtxt = bmp.tostring() 
        self.imgsize =  (bmp.size[0], bmp.size[1])
        temp_file = open('c:\\python23\demdata\W140N40.HDR','r')
        temp_file.readline()
        temp_file.readline()
        self.N_ROWS = int(string.split(temp_file.readline())[1])
        self.N_COLS = int(string.split(temp_file.readline())[1])
        temp_file.readline()
        temp_file.readline()
        temp_file.readline()
        temp_file.readline()
        temp_file.readline()
        temp_file.readline()
        self.long_num = float(string.split(temp_file.readline())[1])
        #self.start_long = long_num
        self.lat_num = float(string.split(temp_file.readline())[1])
        #self.start_lat = lat_num
        self.x_scale = float(string.split(temp_file.readline())[1])
        self.y_scale = float(string.split(temp_file.readline())[1])
        #Latitude_Minimum = lat_num - (N_ROWS * y_scale)
        #Latitude_Maximum = lat_num + y_scale
        #Longitude_Minimum = long_num -  x_scale
        #Longitude_Maximum = long_num + (N_COLS * x_scale)
        temp_file.close()
    # << class demdata methods >> (2 of 2)
    def TD(self,coords):    # where Everything is happening
        #hi_num = 0# there?s a master list of elevation for each tile of the DEM data
        #lo_num = 4328# so I could use some kind of look up table but this way is just as easy
        new_line = []
        data_char = ''
        data_line_num = (coords[2] * 16)
        # width of box 8 to 1 data to gif ratio 16 bit variable in a string
        for x in range((coords[1] * 8),(coords[1] + coords[3])  * 8):
            # iterate over height
            data_start = (x * 9600) + (coords[0]  * 16)
            # find start position of rectangle in file (the number 9600 bytes per line
            # should probably be in a variable)
            self.tom.seek(data_start)# move to proper position in file            
            data_char = self.tom.read(data_line_num)# read proper number of bytes
            for i in range(0, len(data_char) - 1, 2):# iterate over the characters by 2s
                # its a 16 bit signed integer which means that there has got to be
                # a more elegant way of doing this but I was lazy
                data_num = struct.unpack('>h',data_char[i:i+2])[0]
                #data_num = (ord(data_char[i]) << 8) | ord(data_char[i+1])                
                #if data_num == 55537:#sea level
                #	data_num = 0
                #if data_num >= 32767:
                #	data_num = -(data_num ^ 65535)
                if data_num == -9999:#sea level
                    data_num = 0

                new_line.append(data_num)

        return new_line
    # -- end -- << class demdata methods >>
# -- end -- << demmod methods >>