JarCastingOutOfFocusQRReader
OutOfFocusQRReader is a library for reading QR Code from out-of-focus images on Android.
This library uses the OpenCV library.
“QR Code” is a registered trademark of DENSO WAVE INCORPORATED.
Install
Download OpenCV
Download the latest version of the OpenCV Android library from the official OpenCV web page.
Extract zip and move SDK folder
Extract the files the downloaded zip file and move the SDK folder to your project root folder.
Install OpenCV SDK
Edit the settings.gradle file in your project and sync your project:
// add
include ':sdk'
Install OutOfFocusQRReader
Edit the build.gradle file in your project:
repositories {
mavenCentral()
}
dependencies {
// OpenCV sdk
implementation project(':sdk')
// core
implementation 'com.github.soranakk.oofqrreader:oofqrreader:1.0.0'
}
Usage
Create ImageData
Example using Camera2API
dependencies {
...
implementation 'com.github.soranakk.oofqrreader:image-converter-android-camera:1.0.0'
}
val imageConverter = Camera2ApiImageConverter()
ImageReader.newInstance(width, height, ImageFormat.YUV_420_888, 1)
.apply {
setOnImageAvailableListener({ reader ->
reader?.acquireLatestImage()?.let { image ->
val imageData = imageConverter.convertImage(image)
... read QR Code
image.close()
}
}, workerHandler)
Example using CameraXAPI
dependencies {
...
implementation 'com.github.soranakk.oofqrreader:image-converter-androidx-camera:1.0.0'
}
val imageConverter = CameraXApiImageConverter()
val imageAnalysis = ImageAnalysis.Builder()
.setTargetRotation(Surface.ROTATION_0)
.setTargetResolution(Size(1280, 720))
.setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST)
.build()
.also {
it.setAnalyzer(cameraExecutor, ImageAnalysis.Analyzer { image ->
val imageData = imageConverter.convertImage(image)
... read QR Code
image.close()
})
}
Create QRCodeDecoder
Example using MLKit:
dependencies {
...
implementation 'com.github.soranakk.oofqrreader:decoder-mlkit:1.0.0'
implementation 'com.google.mlkit:barcode-scanning:16.1.1'
}
val mlKitDecoder = MLKitDecoder()
Example using ZXing:
dependencies {
...
implementation 'com.github.soranakk.oofqrreader:decoder-zxing:1.0.0'
implementation "com.google.zxing:core:3.4.1"
}
val zxingDecoder = ZxingDecoder()
If your app require Android minSdkVersion less than 24, see https://github.com/zxing/zxing/issues/1170 and demoApp's build.gradle
Example using OpenCV:
dependencies {
...
implementation 'com.github.soranakk.oofqrreader:decoder-opencv:1.0.0'
}
val openCVDecoder = OpenCVDecoder()
Read QR code
val qrReader = MultiFilterQRCodeReader(someDecoder)
val result = qrReader.detectAndRead(image)
See demoApp for more info.
Appendix
How to improve accuracy
Estimate the area where a QR code exist
Estimate the area where a QR code exists by using the large contrast between the QR code and the background.
- Make the input image grayscale
- Binarize with Otsu's method
- Use
Imgproc.erodeto thicken the dots in a QR code and turn them into black squares. - Use
Imgproc.findContoursto get the black square area
Adjust the image
Further improve the accuracy by processing the image of the estimated area using various Image Filters. The features of each ImageFilter implemented are as follows.
GaussianThresholdFilter
Binarize with a weighted average using Gaussian as a threshold at a fixed block size.
Input image
Estimate the area where a QR code exists
After applying the image filter
ThresholdOtsuFilter
Binarize Otsu's method.
Input image
Estimate the area where a QR code exists
After applying the image filter
OverexposureFilter
A filter for reading overexposed QR codes by setting a threshold so that even almost white areas become black. Most input images output a black image, but under certain circumstances this filter works well. For example, displaying a QR code on a smartphone will result in overexposure due to the strong backlight of the smartphone.
Input image
Estimate the area where a QR code exists
After applying the image filter
