Month: September 2015

Create a Video From Your Processing Sketch (Using the IDE)

A quick example to show how to create a video from Processing 2.0 . Here, I’m using the Python mode. We write each frame out to a file and then use the built-in Movie Maker to create a QuickTime video (you can also attach audio if you desire).

Example code:

def setup():
    size(500, 500)
    fill(0)

def draw():
    background(255, 255, 255)

    if mousePressed:
        ellipse(mouseX, mouseY, 80, 80)

    saveFrame("frames/frame-#####.png")

For those that aren’t familiar, this just configures the canvas and then constantly clears the canvas with each redraw. If you’re pressing the mouse-button, it’ll draw a circle whereever the cursor is. After the redraw, it’ll capture one PNG image. It’ll implicitly create the “frames” folder if it doesn’t already exist.

Now, we open Movie Maker:

Open Move Maker

Click on the top “Choose…” button to elect your “frames” directory (or whatever you called it):

Dialog

Click “Create Movie…”, select your video-file name/path, and watch it go:

Make Movie

The final result (in my case):

Final Result

For a library-based approach, look into GSVideo.

Drawing to a Video Using OpenCV and Python

I ran into a considerable amount of difficulty writing a video-file using OpenCV (under Python). Almost every video-writing example on the Internet is only concerned with capturing from a webcam, and, even for the relevant examples, I kept getting an empty/insubstantial file.

In order to write a video-file, you need to declare the FOURCC code that you require. I prefer H.264, so I [unsuccessfully] gave it “H264”. I also heard somewhere that since H.264 is actually the standard, I needed to use “X264” to refer to the codec. This didn’t work either. I also tried “XVID” and “DIVX”. I eventually resorted to trying to pass (-1), as this will allegedly prompt you to make a choice (thereby showing you what options are available). Naturally, no prompt was given and yet it still seemed to execute to the end. There doesn’t appear to be a way to show the available codecs. I was out of options.

It turns out that you still have one or more raw-format codecs available. For example, “8BPS” and “IYUV” are available. MJPEG (“MJPG”) also ended-up working, too. This is the best option (so that we can get compression).

It’s important to note that the nicer codecs might’ve not been available simply due to dependencies. At one point, I reinstalled OpenCV (using Brew) with the “–with-ffmpeg” option. This seemed to pull-down XVID and other codecs. However, I still had the same problems. Note that, since this was installed at the time that I tested “MJPG”, the latter may actually require the former.

Code, using MJPEG:

import cv2
import cv
import numpy as np

_CANVAS_WIDTH = 500
_CANVAS_HEIGHT = 500
_COLOR_DEPTH = 3
_CIRCLE_RADIUS = 40
_STROKE_THICKNESS = -1
_VIDEO_FPS = 1

def _make_image(x, y, b, g, r):
    img = np.zeros((_CANVAS_WIDTH, _CANVAS_HEIGHT, _COLOR_DEPTH), np.uint8)
    position = (x, y)
    color = (b, g, r)
    cv2.circle(img, position, _CIRCLE_RADIUS, color, _STROKE_THICKNESS)

    return img

def _make_video(filepath):
    # Works without FFMPEG.
    #fourcc = cv.FOURCC('8', 'B', 'P', 'S')

    # Works, but we don't have a viewer for it.
    #fourcc = cv.CV_FOURCC('i','Y','U', 'V')

    # Works (but might require FFMPEG).
    fourcc = cv.CV_FOURCC('M', 'J', 'P', 'G')

    # Prompt. This never works, though (the prompt never shows).
    #fourcc = -1

    w = cv2.VideoWriter(
            filepath,
            fourcc,
            _VIDEO_FPS,
            (_CANVAS_WIDTH, _CANVAS_HEIGHT))

    img = _make_image(100, 100, 0, 0, 255)
    w.write(img)

    img = _make_image(200, 200, 0, 255, 0)
    w.write(img)

    img = _make_image(300, 300, 255, 0, 0)
    w.write(img)

    w.release()

if __name__ == '__main__':
    _make_video('video.avi')