How to flip and rotate the camera image?

Yocto
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I’m currently working on a project where I need to manipulate the camera. Specifically, I’m trying to flip and rotate the camera image but I’m not sure how to achieve this.

I’m using IoT Yocto, and I want to flip the image horizontally (mirror effect) and rotate it by 90 degrees.

Could someone guide me on how to implement this? Any code examples or references would be greatly appreciated!

12

Use MDP to flip and rotate the camera image

MDP is an image processing hardware that exists in the SoC and can be used through the v4l2 API or Gstreamer - v4l2convert.

The MDP video device has properties that can be set to rotate, flip,

 horizontal_flip 0x00980914 (bool) : default=0 value=0
 vertical_flip 0x00980915 (bool) : default=0 value=0
 rotate 0x00980922 (int) : min=0 max=270 step=90 default=0 value=0 flags=modify-layout

In addition to setting the property, you also need to set the corresponding output buffer size. For example, if the input buffer is 1280*720 and is rotated 90 degrees, the output buffer will become 720*1280.

Here are some examples to rotate and flip the camera input through v4l2convert (mdp):


# Original:
gst-launch-1.0 -v v4l2src device=${VIDEO_DEV[0]} ! video/x-raw,width=1280,height=720,format=YUY2 ! v4l2convert output-io-mode=dmabuf-import capture-io-mode=dmabuf extra-controls="cid" ! 'video/x-raw, format=NV12' ! queue ! waylandsink

# Rotate 90 degrees:
gst-launch-1.0 -v v4l2src device=${VIDEO_DEV[0]} ! video/x-raw,width=1280,height=720,format=YUY2 ! v4l2convert output-io-mode=dmabuf-import capture-io-mode=dmabuf extra-controls="cid,rotate=90" ! 'video/x-raw, width=720, height=1280, pixel-aspect-ratio=(fraction)1/1, format=NV12' ! queue ! waylandsink

# horizontal flip
gst-launch-1.0 -v v4l2src device=${VIDEO_DEV[0]} ! video/x-raw,width=1280,height=720,format=YUY2 ! v4l2convert output-io-mode=dmabuf-import capture-io-mode=dmabuf extra-controls="cid,horizontal_flip=1" ! 'video/x-raw, format=NV12' ! queue ! waylandsink

# horizontal flip + Rotate 180 degrees:
gst-launch-1.0 -v v4l2src device=${VIDEO_DEV[0]} ! video/x-raw,width=1280,height=720,format=YUY2 ! v4l2convert output-io-mode=dmabuf-import capture-io-mode=dmabuf extra-controls="cid,rotate=180,horizontal_flip=1" ! 'video/x-raw, pixel-aspect-ratio=(fraction)1/1, format=NV12' ! queue ! waylandsink

# vertical flip:
gst-launch-1.0 -v v4l2src device=${VIDEO_DEV[0]} ! video/x-raw,width=1280,height=720,format=YUY2 ! v4l2convert output-io-mode=dmabuf-import capture-io-mode=dmabuf extra-controls="cid,vertical_flip=1" ! 'video/x-raw, format=NV12' ! queue ! waylandsink

# vertical flip + Rotate 270 degrees:
gst-launch-1.0 -v v4l2src device=${VIDEO_DEV[0]} ! video/x-raw,width=1280,height=720,format=YUY2 ! v4l2convert output-io-mode=dmabuf-import capture-io-mode=dmabuf extra-controls="cid,rotate=270,vertical_flip=1" ! 'video/x-raw, width=720, height=1280, pixel-aspect-ratio=(fraction)1/1, format=NV12' ! queue ! waylandsink