PIL was quite slow for my purposes, and it had some issues running under Parallel Python.
I've created a few modifications that should make it easier for others to simply import and start using this.
I should point out that this is by no means infallible, and if you are creating dynamically sized images, be sure to test the extremes to make sure the files are readable. I have had problems with some programs reading generated files around 200k in size. I suspect simply modifying the header using something like this (
http://www.fastgraph.com/help/bmp_header_format.html) as a reference would fix that.
import BMPWriter
header = BMPWriter.default_bmp_header
...(as in test code)
#!/usr/bin/python
import struct, random
# modified from http://pseentertainmentcorp.com/smf/index.php?topic=2034.0
# important values: offset, headerlength, width, height and colordepth
# This is for a Windows Version 3 DIB header
# You will likely want to customize the width and height
default_bmp_header = {'mn1':66,
'mn2':77,
'filesize':0,
'undef1':0,
'undef2':0,
'offset':54,
'headerlength':40,
'width':200,
'height':200,
'colorplanes':0,
'colordepth':24,
'compression':0,
'imagesize':0,
'res_hor':0,
'res_vert':0,
'palette':0,
'importantcolors':0}
def bmp_write(header, pixels, filename):
'''It takes a header (based on default_bmp_header),
the pixel data (from structs, as produced by get_color and row_padding),
and writes it to filename'''
header_str = ""
header_str += struct.pack('<B', header['mn1'])
header_str += struct.pack('<B', header['mn2'])
header_str += struct.pack('<L', header['filesize'])
header_str += struct.pack('<H', header['undef1'])
header_str += struct.pack('<H', header['undef2'])
header_str += struct.pack('<L', header['offset'])
header_str += struct.pack('<L', header['headerlength'])
header_str += struct.pack('<L', header['width'])
header_str += struct.pack('<L', header['height'])
header_str += struct.pack('<H', header['colorplanes'])
header_str += struct.pack('<H', header['colordepth'])
header_str += struct.pack('<L', header['compression'])
header_str += struct.pack('<L', header['imagesize'])
header_str += struct.pack('<L', header['res_hor'])
header_str += struct.pack('<L', header['res_vert'])
header_str += struct.pack('<L', header['palette'])
header_str += struct.pack('<L', header['importantcolors'])
#create the outfile
outfile = open(filename, 'wb')
#write the header + pixels
outfile.write(header_str + pixels)
outfile.close()
def row_padding(width, colordepth):
'''returns any necessary row padding'''
byte_length = width*colordepth/8
# how many bytes are needed to make byte_length evenly divisible by 4?
padding = (4-byte_length)%4
padbytes = ''
for i in range(padding):
x = struct.pack('<B',0)
padbytes += x
return padbytes
def pack_color(red, green, blue):
'''accepts values from 0-255 for each value, returns a packed string'''
return struct.pack('<BBB',blue,green,red)
def pack_hex_color(hex_color):
'''accepts RGB hex colors like '#ACE024', returns a packed string'''
base = 16
red = int(hex_color[1:3], base)
green = int(hex_color[3:5], base)
blue = int(hex_color[5:7], base)
return pack_color(red, green, blue)
###################################
def test():
header = default_bmp_header
header["width"] = 150
header["height"] = 50
#Function to generate a random number between 0 and 255
def rand_color():
x = random.randint(0,255)
return x
#Build the byte array. This code takes the height
#and width values from the dictionary above and
#generates the pixels row by row. The row_padding
#stuff is necessary to ensure that the byte count for each
#row is divisible by 4. This is part of the specification.
pixels = ''
for row in range(header['height']-1,-1,-1):# (BMPs are L to R from the bottom L row)
for column in range(header['width']):
r = rand_color()
g = rand_color()
b = rand_color()
pixels += pack_color(r, g, b)
pixels += row_padding(header['width'], header['colordepth'])
#call the bmp_write function with the
#dictionary of header values and the
#pixels as created above.
bmp_write(header, pixels, "test.bmp")
if __name__ == '__main__':
test()
