Having trouble scanning some PDF417 barcodes

[stephen-gobin]

Expected Behaviour

To scan all the examples of PDF417 found here

https://www.activebarcode.com/codes/pdf417.html

as well as large barcodes found on ID cards

Actual Behaviour

The largest code with ECL5 will not scan nor will my MD DL card

Reproduce Scenario (including but not limited to)

I printed the page out, cut out the individual codes and scanned them one by one. I also confirmed the largest scanned with a downloaded app.

Steps to Reproduce

Platform and Version (eg. Android 5.0 or iOS 9.2.1)

Android 6.0

(Android) What device vendor (e.g. Samsung, HTC, Sony...)

Lenovo TB3-730F

Cordova CLI version and cordova platform version

cordova --version

7.0.1

cordova platforms

android 6.2.3

Plugin version

6.0.8

Sample Code that illustrates the problem

I used the sample code provided

Logs taken while reproducing problem

[andersborgabiro]

This is probably due to the camera not having pixels enough in the preview mode to be able to see each pixel distrinctly. I've had that problem with PDF417 and I rendered maps of what the barcode algorithm in Zxing sees, and I concluded:

• Preview pictures are thresholded, so the algorithm only sees a 1-bit-per-pixel bitmap
• I easily came very close to or even under the preview resolution, that is much lower than the full camera resolution
  For the above to work well, there needs to be roughly 3 steady pixels per barcode module. You can easily calculate if you are close to that.

An improvement to Zxing would be to use grayscale maps instead, as well as take full-resolution photos, but as noted, that's not how Zxing works.

I actually lost a consulting assignment due to smartphones not being up to the task of reading such extreme PDF417 codes. In other words, not my fault, but it became my fault. In my case I even had to implement PDF417 Compact in Zxing, that is even hairier to scan, as there's no end marker to lock on to.

[cristianchaparroa]

Hi guys apparently I've the same issue, with Android (LG Xcam) I read the PDF417 image (my country identification) and I get the long text decode, but with IOS (Iphone 7) I get just the first 10 chars, what can I do for decode the hole barcode?

[andersborgabiro]

Before concluding it's an error in the actual decoding, rather than a resolution problem: Have you tried printing out the barcode larger so that there's a greater chance the camera can focus? The iPhone 7 might have a lower resolution video preview than the LG. PDF417 tends to be printed very small.

[cristianchaparroa]

@andersborgabiro well, I can't print the barcode because is my identification and I don't have the image source, so I took a photograph and I printed it bigger, but I can't scan nothing, so is there a way to modify the resolution video preview over IPhone 7 to check your suggestion?

[andersborgabiro]

Fully understandable.

Selection of video preview resolution is handled by Zxing, and there might be a way to change it, but requires making changes to the plugin.

This is about Xamarin, but note the setting: https://stackoverflow.com/questions/42657211/how-to-scan-drivers-license-pdf417-using-xamarin-forms-zxing-on-ios-10-2

[jasj]

iphone have problems reading binary pdf417

for example bytes upper than 127 and lowr to 198 (utf 8 encode) produce and control signal that end the code. This is not an resolution problem as a mention @andresborgabiro due pdf417 with text has no prob'ems

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[jasj]

to fix it is necesary tonchange the outcode from unicode or utf8 to a binnary array, due jsndont handle binary could be an int array

[cristianchaparroa]

@jasj if I understand with Iphone is not possible read complex pdf417 barcodes? I did a whole test with native application with swift and it read's just a little string no more, I can't get the whole string that I can read with Android phones.

[jasj]

Exactly the issue comes with the encode for example a byte with the code 0. El 1 nov. 2017 09:09, "Cristian" <[email protected]> escribió:

…

@jasj <https://github.com/jasj> if I understand with Iphone is not possible read complex pdf417 barcodes? I did a whole test with native application with swift and it read's just a little string no more, I cant get the whole string that I can read with Android phones. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#532 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AFTssQTrXTvD-8aRnL6jX9bJcFO6Bvlfks5syImhgaJpZM4O-_aL> .

[cristianchaparroa]

@jasj So, is there any option to read it?

[jasj]

Using this pluging not yet :(, but a workarround for a while is use a web server and send the image in base64(with previews redice image no more than vesa) El 1 nov. 2017 11:24, "Cristian" <[email protected]> escribió:

…

@jasj <https://github.com/jasj> So, is there any option to read it? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#532 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AFTsscyurqjafRXGpspF1812veO3Plsqks5syKk-gaJpZM4O-_aL> .

[bpetty-formfast]

I have noticed PDF417 problems as well when trying to encode less than 4 characters. For what ever reason it gets them wrong all of the time, so I had to change my demo to ensure that I was scanning a code of at least 4 characters. We later switched to QR, partly due to this problem and because it seemed like it scanned faster on some platforms.

[andersborgabiro]

PDF417 is very sensitive to misalignment etc, so that was a good decision anyway. QR code is much more robust, by design.