Delay when capturing color images

[jonas-hurst]

There seems to be a small delay when capturing color camera images of around 1/3 of a second. Is there a way to get the color images (almost) instantly?

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(This problem has driven me crazy for weeks. I finally found a solution, so I am writing this issue to document a solution for everyone to profit. Solution in comment below.)

[jonas-hurst]

The issue occurs when device color format is set to device_config.color_format = pykinect.K4A_IMAGE_FORMAT_COLOR_MJPG. This is the default setting. Decoding the jpg seems to take some time causing the delay.

When using BGRA32 color format instead, no decoding of the image is necessary. device_config.color_format = pykinect.K4A_IMAGE_FORMAT_COLOR_BGRA32

A conversion between from BGRA to BGR color space is however necessary to show the image with opencv's cv2.imshow() method.

color_image_bgr = cv2.cvtColor(color_image_bgra, cv2.COLOR_BGRA2BGR)

[miraclejzd]

Hi. I tried your solution, and foundd it really efficient!

But there is another question: The color of the image are changed, such as the face of the human turns to blue, which is really strange. Do you know how to resolve it?

[jonas-hurst]

Did you convert to BGR color format? Or do you use an image viewer that does not expect BGR but RGB?

[miraclejzd]

Yeah, I use cv2.cvtColor() to convert it to BGR format. And then I use cv2.imshow() to show the image. Here is part of my code:

    device_config = pykinect.default_configuration
    device_config.color_format = pykinect.K4A_IMAGE_FORMAT_COLOR_BGRA32
    device_config.color_resolution = pykinect.K4A_COLOR_RESOLUTION_1080P
    device_config.depth_mode = pykinect.K4A_DEPTH_MODE_WFOV_2X2BINNED

    device = pykinect.start_device(config=device_config)

    cv2.namedWindow('Color image', cv2.WINDOW_NORMAL)
    while True:
        capture = device.update()

        ret, color_image = capture.get_color_image()
        if not ret:
            continue

        color_image = cv2.cvtColor(color_image, cv2.COLOR_RGBA2BGR)
        cv2.imshow('Color image', color_image)