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# Just to save the user having to install PIL.
# BMP code from: http://pseentertainmentcorp.com/smf/index.php?topic=2034.0
# Distributed with kind permission from James Main <jdmain@comcast.net>
import struct
def WriteBMP(pixels,filename):
'''
Write a BMP to filename from the (r,g,b) triples in pixels[row][column].
Usage example:
WriteBMP( [[(255,0,0),(0,255,0),(255,255,0)],[(0,0,255),(0,0,0),(0,255,255)]], "test.bmp" )
'''
# Here is a minimal dictionary with header values.
d = {
'mn1':66,
'mn2':77,
'filesize':0,
'undef1':0,
'undef2':0,
'offset':54,
'headerlength':40,
'width':len(pixels[0]),
'height':len(pixels),
'colorplanes':1,
'colordepth':24,
'compression':0,
'imagesize':0,
'res_hor':0,
'res_vert':0,
'palette':0,
'importantcolors':0
}
# 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_mod and padding
# stuff is necessary to ensure that the byte count for each
# row is divisible by 4. This is part of the specification.
bytes = ''
for row in range(d['height']-1,-1,-1): # (BMPs are encoded left-to-right from the bottom-left)
for column in range(d['width']):
r,g,b = pixels[row][column]
pixel = struct.pack('<BBB',b,g,r)
bytes += pixel
row_mod = (d['width']*d['colordepth']/8) % 4
if row_mod == 0:
padding = 0
else:
padding = (4 - row_mod)
padbytes = ''
for i in range(padding):
x = struct.pack('<B',0)
padbytes = padbytes + x
bytes = bytes + padbytes
# These header values are described in the bmp format spec.
# You can find it on the internet. This is for a Windows
# Version 3 DIB header.
mn1 = struct.pack('<B',d['mn1'])
mn2 = struct.pack('<B',d['mn2'])
filesize = struct.pack('<L',d['filesize'])
undef1 = struct.pack('<H',d['undef1'])
undef2 = struct.pack('<H',d['undef2'])
offset = struct.pack('<L',d['offset'])
headerlength = struct.pack('<L',d['headerlength'])
width = struct.pack('<L',d['width'])
height = struct.pack('<L',d['height'])
colorplanes = struct.pack('<H',d['colorplanes'])
colordepth = struct.pack('<H',d['colordepth'])
compression = struct.pack('<L',d['compression'])
imagesize = struct.pack('<L',d['imagesize'])
res_hor = struct.pack('<L',d['res_hor'])
res_vert = struct.pack('<L',d['res_vert'])
palette = struct.pack('<L',d['palette'])
importantcolors = struct.pack('<L',d['importantcolors'])
# create the outfile
outfile = open(filename,'wb')
# write the header + the bytes
outfile.write(mn1+mn2+filesize+undef1+undef2+offset+headerlength+width+height+\
colorplanes+colordepth+compression+imagesize+res_hor+res_vert+\
palette+importantcolors+bytes)
outfile.flush()
outfile.close()
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