Passing it as a string will be cumbersome.. you can do this a lot more efficient.
If you pass it as a single, or a set of numbers, it will become a lot more compressed 
ie: use the binary representation of the number
11000011 = 195
01100110 = 102
00111100 = 60
00011000 = 24
4 numbers, 1 per line of pixels
This 'bitmap' would represent a V
While what PaulS says is true, that only the black pixels matter.. do not ignore the 'white' pixels.
It is possible to heavily compress a bitmap (see above), but if you'd send a list of black pixels with their location, it becomes a lot harder to compress it to useable sizes.