[Bug/Feature] Pixel 2 XL Not Scanning When QR Code is Exact Fit in ViewFinder about code-scanner HOT 11 CLOSED

Hello.
As I think, what is really counterintuitive - if code outside of frame rect will be recognized.
Btw, I see another soulution, make real recognition area a bit larger than viewfinder frame.
I'll implement something like this in next version.

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Seems like the problem isn't in frame or scanning area. It is in ZXing library itself. Because when you scan from small distance from screen, phone's camera sees different subpixels (RGB) and the library can't decode such images well.

Example in attached screenshot.

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Hello.
As I think, what is really counterintuitive - if code outside of frame rect will be recognized.
Btw, I see another soulution, make real recognition area a bit larger than viewfinder frame.
I'll implement something like this in next version.

The solution you mentioned is what I was proposing in the original post albeit it could have a different approach to do it. Apologies if I wasn't clear enough on that. I am willing to discuss and do the implementation if you agree with the solution we arrive at

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I've already implemented this, and it got no result even with 20% larger area (on Galaxy S7). See my last comment. I'll get Pxel 2 XL in a couple of weeks and test library.
Anyways, completely ignore the frame is bad idea.

Or, the promlem can be in preview image size. I never tested library at 2:1 screens before.

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Just some more info

I have not been able to reproduce this issue on Samsung Galaxy S8 which I believe also has the same screen aspect ratio. The issue seems to just be for Pixel 2 and Pixel 2 XL Devices. (AFAIK based on my testing)

Edit:
I tested on S7 Edge Running Nougat and didn't encounter this issue. Let me get a screenshot of how far the Pixel 2 has to be before recognizing.

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So, this problem should be investigated deeper. I'll kep this issue open.
What parameters of scanner view are you using? (full screen or not, viewfinder aspect ration, etc)
Portrait or landscape orientation?

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Just off the top of my head, do you think it would improve the reliability of the decoder if we did a high contrast filter on the frame before decoding it? Edit: Now that I think about it, they could be doing that in the Zxing library internally as well

Edit: My Config (Orientation Portrait), Full Screen, Aspect Ratio 1:1
codeScanner = CodeScanner(it, codeScannerView)
codeScanner?.isFlashEnabled = false
codeScanner?.isAutoFocusEnabled = true
codeScanner?.setFormats(CodeScanner.ALL_FORMATS)
codeScanner?.setDecodeCallback(this@QRFragment)
codeScanner?.setErrorCallback(this@QRFragment)
codeScanner?.setScanMode(ScanMode.CONTINUOUS)

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I was able to resolve this issue by reapplying your threshold changes and also utilizing a smaller frameSize (was added in my previous PR). Now it scans perfectly for me. I've made it so that the threshold is configurable and is 0 by default (existing behavior) and opened a PR so you can take a look at the code

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So I investigated this issue some more. I thought I had resolved the issue with the changes mentioned above but then on a different monitor, it did not work (most likely due to the subpixels issue you mentioned briefly above)

The next thing I tried was changing the LuminanceSource from PlanarYUV to RGB and that actually ended up resolving that issue. I will test on various devices and monitors/screens to ensure it works consistently and then make a PR.

One thing to note. I think that not all devices actually support RGB mode for the Camera so I am currently converting the cropped frame ONLY to RGB and creating a RGBLuminanceSource

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Hm, I don't think that such conversions is the best way to resolve this issue.
And it's really wired how changing color format helps recognition.

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Seems like the promlem is in subpixel and/or noise. For now, this can't be fixed in my library. However, I'll keep by library up to date with ZXing.

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