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Target Overlay Misaligns After Flip

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Running a Six Hexapod (EZ-Robot) with the EZ-B Wi-Fi camera mounted upside down under the top plate, connected over Wi-Fi to ARC on Windows. I’m using Camera Device at 640x480 and added the Target Overlay skill to put a crosshair PNG over the video to help center the robot before walking. The overlay looks centered initially, but when I correct the camera orientation in Camera Device (Flip Vertical or Rotate 180), the Target Overlay doesn’t appear to follow that transform-the crosshair is no longer in the true center of the video and sometimes shifts slightly toward the top-left. If I change the Camera Device resolution from 320x240 to 640x480, the overlay also seems stretched or offset, even when I reattach.

What I’ve tried:

  • Created PNGs that exactly match the camera resolution (320x240 and 640x480) with transparent backgrounds.
  • Toggled Attach/Detach and reloaded the image after changing flip/rotation.
  • Docked/undocked and resized the camera panel to see if it’s a UI scaling issue.
  • Init script to re-attach on startup:
ControlCommand("Target Overlay", "Detach")
Sleep(200)
ControlCommand("Camera Device", "Start")
Sleep(500)
ControlCommand("Target Overlay", "LoadImage", "C:\overlays\crosshair_640x480.png")
ControlCommand("Target Overlay", "Attach", "Camera Device")

Is there a supported way to have Target Overlay inherit the Camera Device’s flip/rotate and resolution changes on the Six’s camera feed, or should I pre-rotate/mirror per resolution and then auto-attach via ControlCommand on project start?


Related Hardware (view all EZB hardware)
Six Hexapod
Six Hexapod by EZ-Robot
Six hexapod robot kit: Canadian-designed, customizable WiFi 6-legged platform with 12 servos/12 DOF for dynamic motion. Available at EZ-Robot.
Wi-Fi / USB
Servos 24
Camera
Audio
UART 3
I2C
ADC 8
Digital 24

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Camera Device by Synthiam
Use PC or robot cameras for vision tracking: color, QR, glyph, face, object, motion; record video/data, control servos and movement, run scripts
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Picture In Picture by Synthiam
Picture-in-picture camera overlay: superimpose one camera onto another; configure source/destination, position, size, border, processed frames, and swap
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Yes - what you’re seeing makes sense.

Why it happens

Target Overlay does not inherit the camera’s internal image transform settings from Camera Device.

So when you apply:

  • Flip Vertical
  • Rotate 180
  • resolution changes like 320x240 640x480

the camera feed being displayed changes, but the overlay image is still drawn using its own coordinate space and sizing behavior. That’s why it can look:

  • offset toward the top-left
  • slightly shifted after rotation/flip
  • stretched or mismatched after a resolution change

What to do instead

Best practice

Use an overlay image that already matches the final displayed camera orientation and resolution.

That means:

  • if the camera is mounted upside down, make the overlay PNG already rotated/mirrored to match the corrected view
  • create separate PNGs for each resolution you use, such as:
    • crosshair_320x240.png
    • crosshair_640x480.png

Then load the correct one after the camera starts.

For your Six Hexapod camera setup, I’d suggest:

  1. Set the Camera Device transform first
    • Flip/Rotate as needed
  2. Set the camera resolution
  3. Load the matching overlay PNG for that exact output
  4. Attach the overlay after the camera is fully started

Your startup script approach is the right idea, but I’d make sure the camera is fully active before attaching the overlay.

Example:

ControlCommand("Camera Device", "CameraStart")
sleep(1000)
ControlCommand("Target Overlay", "LoadImage", "C:\\overlays\\crosshair_640x480.png")
sleep(200)
ControlCommand("Target Overlay", "Attach", "Camera Device")

If your overlay skill has a configurable image mode or placement settings in the kebab menu, check those too. In ARC, each robot skill’s settings are in the three-line menu on the skill window.

Important limitation

There currently isn’t a built-in "inherit camera transform" feature for overlay skills like that. So the overlay won’t automatically mirror the camera’s flip/rotate state unless the skill itself was designed to do that.

If you want it fully dynamic

If you need this to adapt automatically when you change resolution or orientation, the cleanest approach is to create a small custom robot skill that reads the camera dimensions and draws the crosshair programmatically.

That’s exactly the kind of thing ARC’s custom skill system is for: https://synthiam.com/Support/Create-Robot-Skill/Overview

If you want, I can help you sketch a simple JavaScript-based ARC script or a custom robot skill approach to draw a centered crosshair without needing separate PNGs.

Quick question

Which exact skill are you using for the overlay - Target Overlay, Picture in Picture, or a different camera overlay skill? If you share that, I can tell you whether there’s a specific setting in its kebab menu that helps with alignment.

I am a customer support AI and still learning. Please verify important answers in our support documentation. For advanced AI features, use the AI Script Agent built into ARC.
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