Getting player names from Twitch streams or an exercise in futility

I had an idea last month for a site based around identifying video game streamers while they are in game. If I can identify them in real time then I could have real time fantasy league style betting based around the stats... it was a fun experiment but my techniques ended up not being very practical.

The Idea

In the game League of Legends I could try to find the "yellow health bar" that only your character has. Once I have the coordinates for the yellow health bar I can look above it to see the character name! Boom, with the character name I can look up stats and track all of their games automatically.

The process

For example, watching Krepo's stream here's how I'd go about getting his character name.

Get the stream frame

from livestreamer import Livestreamer

while True:
    session = Livestreamer()
    streams = session.streams('' % streamer)
    if streams:
        stream = streams['source']

        container =
        video_stream = next(s for s in container.streams if s.type == b'video')

        image = None
        for packet in container.demux(video_stream):
            for frame in packet.decode():
                image = frame.to_image()
                features = process_image(image)

Original Stream Image

Find yellow health bar

def _find_our_champion(image, search_step=2, draw_on_image=False):
    # should find the yellow bar underneath our hero and then 
    # we can use the top left of that to center our search area
    data = np.asarray(image)
    # remove any alpha channel in the data so we just have (r, g, b)
    data = data[:, :, :3]
    width, height = data.shape[1], data.shape[0]
    character_name_coords = None

    # Cut off the bottom few hundred pixels, not needed
    height -= 200

    for y in xrange(0, height):
        hits_this_row = 0
        for x in xrange(0, width, search_step):
            r, g, b = data[y][x]
            if r > 200 and 160 < g < 230 and 30 < b < 70:
                # really yellow
                hits_this_row += 1
            if hits_this_row > 20:
                # Top left and bottom right
                character_name_coords = (x - 120, y - 35, x + 100, y - 8)
                if draw_on_image:
                    red = (255, 0, 0)
                    draw = ImageDraw.Draw(image)
                    draw.rectangle(character_name_coords, fill=red)
        if character_name_coords:
    return character_name_coords

Character name image

Process the image

def _ocr_name_box(name_box_image):
    # 0 means load in grayscale
        gray = cv2.cvtColor(np.array(name_box_image), 0)
    except TypeError:
        gray = cv2.cvtColor(name_box_image, 0)
    ret, gray = cv2.threshold(gray, 160, 255, cv2.THRESH_BINARY)

    # ocr code below

Character name image processed

OCR the final processed image

def _ocr_name_box(name_box_image):
    # processing code above

    gray_image = Image.fromarray(gray)
    return pytesseract.image_to_string(gray_image)

OCR results: Krepo

So, it worked in this particular case... this was one of the few that did work.

The results


The idea was super fun to pursue but it doesn't perform very well for a few reasons:

  • Streamers can disable showing character name
  • The "yellow health bar" specific to your character can be disabled
  • What region are players on?
  • PyTesseract is pretty cool but Tesseract is pretty cumbersome to use. Hard to train, seems kind of outdated but definitely decent for being free!
  • The OCR results were pretty bad although I'm sure with mechanical turk + some training we could get it in a decent state, but still.. names could not be shown at all!

So... it was a fun experiment but not very practical!

You can find all the source here.

— 16 December 2015
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