I am trying to import a QR code from a .png file and decode it using Zxing.Net.Mobile and ZXing.Net.Mobile.Forms .
If I scan the QR code using the ZXing.Mobile.MobileBarcodeScanner
class, the decoding works as required, however, when importing it from a file, the Qr code reader ( ZXing.QrCode.QRCodeReader()
) decode function always returns null
.
As I'm using Xamarin Forms ; each platform handles the bitmap/image creation and the portable part handle the rest ( Zxing BinaryBitmap
creation and decoding).
//Store rawBytes and image demensions
PotableBitmap bMap = DependencyService.Get<IBitmap>().FileToBitmap(filePath);
RGBLuminanceSource source = new RGBLuminanceSource(bMap.RgbBytes, bMap.Width, bMap.Height, RGBLuminanceSource.BitmapFormat.RGB32);
HybridBinarizer binarized = new HybridBinarizer(source);
BinaryBitmap bitmap = new BinaryBitmap(binarized);
var reader = new ZXing.QrCode.QRCodeReader();
data = reader.decode(qrCodeBitmap); // This is always null
The DependencyService
will call the platform specific function, at the moment I am working with Andorid so, the function is as follows:
public PortableBitmap FileToBitmap(string ms)
{
var bytes = File.ReadAllBytes(ms);
Android.Graphics.Bitmap bMap = BitmapFactory.DecodeByteArray(bytes, 0, bytes.Length);
int[] intArray = new int[bMap.Width * bMap.Height];
bMap.GetPixels(intArray, 0, bMap.Width, 0, 0, bMap.Width, bMap.Height)
List<byte> result = new List<byte>();
foreach (int intRgb in intArray)
{
Color pixelColor = new Color(intRgb);
result.Add(pixelColor.R);
result.Add(pixelColor.G);
result.Add(pixelColor.B);
}
return new PortableBitmap(result.ToArray(), bMap.Width, bMap.Height);
}
I have looked through some of the posts on SO that are having the same problem and have tried the following:
BitmapLuminanceSource
: still returns null
and requires the use of another libraryRGBLuminanceSource
: RGB32, BGR32, ARGB32, ABGR32 (each time changing the FileToBitmap function)Binarizer
, GlobalHistogramBinarizer()
MultiFormatReader()
with the Pure barcode and try harder hints Here is where the return null
is made:
private FinderPattern[] selectBestPatterns()
{
int startSize = possibleCenters.Count;
if (startSize < 3)
{
// Couldn't find enough finder patterns
return null; // It returns here
}
...
The online Zxing decoder can decode the QR code I'm testing correctly. Here is my test QR code:
I solved that problem, with this method in the Android implementation to return an RGBLuminanceSource from the path of the image
public RGBLuminanceSource GetRGBLuminanceSource(string imagePath)
{
if (File.Exists(imagePath))
{
Bitmap bitmap = BitmapFactory.DecodeFile(imagePath);
List<byte> rgbBytesList = new List<byte>();
for (int y = 0; y < bitmap.Height; y++)
{
for (int x = 0; x < bitmap.Width; x++)
{
var c = new Color(bitmap.GetPixel(x, y));
rgbBytesList.AddRange(new[] { c.A, c.R, c.G, c.B });
}
}
byte[] rgbBytes = rgbBytesList.ToArray();
return new RGBLuminanceSource(rgbBytes, bitmap.Height, bitmap.Width, RGBLuminanceSource.BitmapFormat.ARGB32);
}
return null;
}
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