Overlay Text with OpenCV in CustomEncoder

[Altair68]

Is it possible to overlay a given Text with a CustomEncoder?
This is a snippet of what I'm trying to do:

import picamera
import picamera.mmal as mmal
import sys
import numpy as np

class MyEncoder(picamera.PiCookedVideoEncoder):
    def start(self, output, motion_output=None):
        super(MyEncoder, self).start(output, motion_output)

    def _callback_write(self, buf):

        bufData = buf[0].data

        data = np.fromstring(bufData, dtype=np.uint8)
        image = cv2.imdecode(data, 1)

        #This is where I'd cv2.putText(...)

        super(MyEncoder, self)._callback_write(buf)


class MyCamera(picamera.PiCamera):
    def __init__(self):
        super(MyCamera, self).__init__();

    def _get_video_encoder(self, camera_port, output_port, format, resize, **options):
        return MyEncoder(self, camera_port, output_port, format, resize, **options)


with MyCamera() as camera:
    while True:
        camera.start_recording(sys.stdout, format='h264')
        camera.wait_recording(60 *60 * 24)
        camera.stop_recording()

With that code "camera.stop_recording()" raises "TypeError: 'MMALBuffer' object does not support indexing".

Or is there an easier way of doing what I'm trying to do here?

[Berryfier]

See my issue #337 on removing the indexing error.

[Altair68]

So basically adding key=0 as a parameter should do the trick?

[Berryfier]

The interactive help identifies key=0, but this may be a default. For me the removal of [0] after buf was sufficient.

[Altair68]

Ahhh now I see! 👍 Thanks a lot :)

[waveform80]

If you just want to overlay text, see the annotate_text property.

Unfortunately what you're trying to do (modify the image in the encoder class) isn't going to work: the encoder callback is at the very end of the pipeline after the image has been encoded and is about to be written to the output. What I think you're wanting to do is modify the image before it gets to the encoder; that's not (currently, easily) possible with picamera.