Question: How to configure detection boundaries for image. processing purpose through 'onImageForAnalysis'

[CuriousDev21]

Hello,

Thank you for the efforts put into making such a comprehensive camera plugin.

I wanted to ask about a use case I am having:

• displaying the camera preview with an overlay. I read that it is possible through the custom builder.
• The overlay shows the a rectangle/square in the middle indicating the target capture frame.
• The idea is to only live capture the image within the bounds of that rectangle and process it for barcode scanning/object detection.

My current challenge is knowing how and if is possible to configure the 'onImageForAnalysis' to capture images only within the bounds of that overlayed rectangle.

Any help appreciated.

Merci,

[apalala-dev]

Hello,

Thanks for the feedback!

• Displaying some kind of indicator above the preview is definitively doable, using CameraAwesomeBuilder.custom() or even CameraAwesomeBuilder.awesome() with a previewDecoratorBuilder.
  • In both case, you might take a look at the previewSize and previewRect parameters to correctly place your indicator / detect if barcode is within it
  • More docs on these coming soon
• The image analysis will always "capture" everything the camera can capture. There is no simple way to crop the image efficiently atm.
  • If you plan on using MLKit, here is a comment from them on stackoverflow from early 2021 stating that they'd had the crop feature.
  • Still no news...
  • Even if it's less efficient, you can detect if the barcodes are scanned in your given area using the boundingBox from the recognized barcodes.
  • If it's within your area, use it, otherwise don't do anything.

Keep in mind that most of the time, you can use a low res for image analysis: processing will be much faster. 👍

[apalala-dev]

Hey @Overlord21 ,

I just made a PR with this example in mind. Several changes on master have not yet been published to pub.dev, but you can take a look if you'd like! The PR is #273

[CuriousDev21]

Hey @apalala-dev,

Thank you for the swift reply.

Yes, I can see it the overlay doable with the previewDecoratorBuilder, just the other aspect of object detection only in the rectangular area, is still unclear to me. I am expecting the full image to have many objects, but I only want to analyse the one within the boundaries of the overlayed rectangle.

Will check the PR changes mentioned.

Thanks again for your valuable support!

[apalala-dev]

Translating image analysis coordinates is not super easy, maybe you can try to take the example from the mentioned PR (preview_overlay_example.dart) and add your own code on top of it since it seems to do something very similar to what you want to achieve. That may be easier.

[CuriousDev21]

Thanks, will try to use the preview Overlay example. My input is an image with a remote control device having a list of icons (kinda like a remote control), and the app should try and detect/identify one of the icons only inside the rectangular overlay.

I know it sounds very specific and will require something like a custom RenderRepaintBoundary to translate coordinates and crop images.

[apalala-dev]

Hey @Overlord21 , we've released 1.3 which includes the mentioned PR.

You might want to take a look at the doc of the barcode overlay example.