Output RGB Bytes From Any Source

True Story Follows

So I’m on the grind, straight hustling on an interesting side project. I’m exploring the whacky world of microcontrollers and C blogs that have no CSS on them. And by the time I’ve put something together, I found out that it was dramatically easier than I thought it would be. But the work I did was just a small component of what could otherwise be a gateway to tons of hardware and IOT projects.

The Problem

You have a video file, you want to work with the raw RGB bytes to do something: maybe integrate with a microcontroller, maybe do some whacky IOT stuff…who knows. But here’s how you can easily get the raw RGB bytes from any video source and manipulate in real time:

The Code from cStringIO import StringIO
import sys
# requires Pillow==2.7.0
from PIL import Image
# requires numpy
import numpy as np
BYTES_PER_PIXEL = 3
class PPMState(object):
READ_P6 = 0
READ_WIDTH_HEIGHT = 1
READ_MAX_COLOR = 2
READ_DATA = 3
expected_length = sys.maxint
def get_np_array_from_frame(read_buffer, expected_length, (width, height)):
read_buffer.seek(0)
return np.array(
Image.open(
_image_data_bytes_to_ppm_file(
read_buffer.read(expected_length),
(width, height)
)
)
)
def _image_data_bytes_to_ppm_file(image_data, (width, height)):
ppm_image = StringIO()
ppm_image.write(
"P6\n{width} {height}\n255\n".format(
width=width,
height=height
)
)
ppm_image.write(image_data)
ppm_image.seek(0)
return ppm_image
def generate_np_array_frames_from_std():
current_state = PPMState.READ_P6
read_buffer = StringIO()
for line in sys.stdin:
if current_state == PPMState.READ_WIDTH_HEIGHT and line.startswith("P6"):
current_state = PPMState.READ_P6
if current_state == PPMState.READ_P6:
current_state = PPMState.READ_WIDTH_HEIGHT
elif current_state == PPMState.READ_WIDTH_HEIGHT:
width, height = [int(val) for val in line.split()]
PPMState.expected_length = width * height * BYTES_PER_PIXEL
current_state = PPMState.READ_MAX_COLOR
elif current_state == PPMState.READ_MAX_COLOR:
# unusued, but this could specify colors > 255
int(line) # max color
current_state = PPMState.READ_DATA
elif current_state == PPMState.READ_DATA:
read_buffer.write(line)
if read_buffer.tell() >= PPMState.expected_length:
np_array = get_np_array_from_frame(read_buffer, PPMState.expected_length, (width, height))
read_buffer = StringIO()
current_state = PPMState.READ_WIDTH_HEIGHT
yield np_array
def do_something_with_np_array(np_array):
print np_array
if __name__ == "__main__":
for np_array in generate_np_array_frames_from_std():
do_something_with_np_array(np_array) To Run

ffmpeg -i <my_video_file.avi> -c:v ppm -f rawvideo - < /dev/null | python file_i_just_created.py