"Invalid stride" error after duplex scan with Canon P-208II

[dominikbayerl]

Hi!

I am not sure if I should file a bug report for this, so if in doubt I'll just post here instead.
When I try to scan a Duplex page with my Canon P-208II scanner, I sometimes receive an error during processing of the second page. I am using the TWAIN default backend. I tried to do some debugging on this and the exception seems to happen in

naps2/NAPS2.Images/Bitwise/PixelInfo.cs

Lines 5 to 25 in 7a2ecff

	public PixelInfo(int width, int height, SubPixelType subPixelType, int stride = -1, int strideAlign = -1)
	{
	var minStride = (width * subPixelType.BitsPerPixel + 7) / 8;
	if (stride == -1)
	{
	stride = minStride;
	}
	else if (stride < minStride)
	{
	throw new ArgumentException("Invalid stride");
	}
	if (strideAlign > 0)
	{
	stride = (stride + (strideAlign - 1)) / strideAlign * strideAlign;
	}
	Width = width;
	Height = height;
	SubPixelType = subPixelType;
	Stride = stride;
	Length = stride * height;
	}

I inspected the passed TwainMemoryBuffer memoryBuffer object in a debugger. The object looks like this:

  "buffer": "[...]"
  "rows": 26,
  "columns": 2504,
  "bytesPerRow": 2504

Obviously the calculation fails, since minStride = (2504 * 24 + 7) / 8 = 7512 and, the passed stride = 2504.
However, I can't really figure out what is wrong here. I attached the debug log below.

I am very thankful about any hints for this issue!

2024-02-04 16:37:15.5537 15044 Debug: Trying to raise event DataTransferredEventArgs on thread 16 without sync. 
2024-02-04 16:37:15.5789 15044 NAPS2.TW - DataTransferred 
2024-02-04 16:37:15.5789 15044 Debug: Trying to raise event DataTransferredEventArgs on thread 16 without sync. 
2024-02-04 16:37:15.5789 15044 NAPS2.TW - DataTransferred 
2024-02-04 16:37:15.5789 15044 Debug: Trying to raise event DataTransferredEventArgs on thread 16 without sync. 
2024-02-04 16:37:15.5789 15044 NAPS2.TW - DataTransferred 
2024-02-04 16:37:15.5789 15044 Debug: Trying to raise event DataTransferredEventArgs on thread 16 without sync. 
2024-02-04 16:37:15.5789 15044 NAPS2.TW - DataTransferred 
2024-02-04 16:37:15.5789 15044 Debug: Trying to raise event DataTransferredEventArgs on thread 16 without sync. 
2024-02-04 16:37:15.5789 15044 NAPS2.TW - DataTransferred 
2024-02-04 16:37:15.5789 15044 Debug: Trying to raise event DataTransferredEventArgs on thread 16 without sync. 
2024-02-04 16:37:15.5789 15044 NAPS2.TW - DataTransferred 
2024-02-04 16:37:15.5838 15044 Debug: Trying to raise event DataTransferredEventArgs on thread 16 without sync. 
2024-02-04 16:37:15.5838 15044 NAPS2.TW - DataTransferred 
2024-02-04 16:37:15.5838 15044 Debug: Trying to raise event DataTransferredEventArgs on thread 16 without sync. 
2024-02-04 16:37:15.5838 15044 NAPS2.TW - DataTransferred 
2024-02-04 16:37:15.5838 15044 NAPS2.TW - StateChanged (to 6) 
2024-02-04 16:37:15.5838 15044 NAPS2.TW - StateChanged (to 5) 
2024-02-04 16:37:15.5838 15044 Debug: Thread 16: DisableSource. 
2024-02-04 16:37:15.5838 15044 NAPS2.TW - StateChanged (to 4) 
2024-02-04 16:37:15.5838 15044 NAPS2.TW - SourceDisabled 
2024-02-04 16:37:15.5838 15044 NAPS2.TW - Finishing with completion 
2024-02-04 16:37:15.5997 15044 Debug: Thread 16: CloseSource. 
2024-02-04 16:37:15.6270 15044 NAPS2.TW - StateChanged (to 3) 
2024-02-04 16:37:15.6270 15044 Debug: Thread 16: CloseManager. 
2024-02-04 16:37:15.6270 15044 NAPS2.TW - StateChanged (to 2) 
2024-02-04 16:37:23.2814 26084 Invalid stride System.ArgumentException: Invalid stride
   at new NAPS2.Images.Bitwise.PixelInfo(int width, int height, SubPixelType subPixelType, int stride, int strideAlign) in naps2/NAPS2.Images/Bitwise/PixelInfo.cs:line 14
   at void NAPS2.Scan.Internal.Twain.TwainMemoryBufferReader.CopyBufferToImage(TwainMemoryBuffer memoryBuffer, TwainImageData imageData, IMemoryImage outputImage) in naps2/NAPS2.Sdk/Scan/Internal/Twain/TwainMemoryBufferReader.cs:line 29
   at void NAPS2.Scan.Internal.Twain.TwainImageProcessor.MemoryBufferTransferred(TwainMemoryBuffer memoryBuffer) in naps2/NAPS2.Sdk/Scan/Internal/Twain/TwainImageProcessor.cs:line 99
   at async Task NAPS2.Remoting.Worker.WorkerServiceAdapter.TwainScan(ScanOptions options, CancellationToken cancelToken, ITwainEvents twainEvents) in naps2/NAPS2.Sdk/Remoting/Worker/WorkerServiceAdapter.cs:line 179
   at async Task NAPS2.Scan.Internal.Twain.RemoteTwainSessionController.StartScan(ScanOptions options, ITwainEvents twainEvents, CancellationToken cancelToken) in naps2/NAPS2.Sdk/Scan/Internal/Twain/RemoteTwainSessionController.cs:line 28
   at async Task NAPS2.Scan.Internal.Twain.TwainScanDriver.Scan(ScanOptions options, CancellationToken cancelToken, IScanEvents scanEvents, Action<IMemoryImage> callback)+(?) => { } in naps2/NAPS2.Sdk/Scan/Internal/Twain/TwainScanDriver.cs:line 43
   at async Task NAPS2.Scan.Internal.RemoteScanController.Scan(ScanOptions options, CancellationToken cancelToken, IScanEvents scanEvents, Action<ProcessedImage, PostProcessingContext> callback) in naps2/NAPS2.Sdk/Scan/Internal/RemoteScanController.cs:line 45
   at async IAsyncEnumerable<ProcessedImage> NAPS2.Scan.ScanController.Scan(ScanOptions options, CancellationToken cancelToken)+(?) => { } in naps2/NAPS2.Sdk/Scan/ScanController.cs:line 144

[cyanfish]

The problem is that the buffer (sent by the Canon driver) reports itself as being full color which implies 3 bytes per pixel, but the bytesPerRow value is only 1 byte per column (pixel), so it's invalid.

There are a few things that could be wrong, that might make this fixable:

1. The color is reported incorrectly, and it's 1-byte-per-pixel grayscale image data.
2. The bytesPerRow is reported incorrectly, and the buffer actually has the full color image data.
3. Something else more complicated.

So the questions I would ask:

1. Are you scanning in color or grayscale?
2. What is buffer.Length and how does it compare to rows * columns? 1x or 3x?
3. If you're so inclined, you could try adding a workaround here that would look like this:

if (memoryBuffer.BytesPerRow == memoryBuffer.Columns && _currentImageData.BitsPerPixel == 24)
{
    memoryBuffer.BytesPerRow = memoryBuffer.Columns * 3;
    _logger.LogDebug("NAPS2.TW - Test fix for P-208II");
}

[cyanfish]

Oh, and while I'd like to fix this in NAPS2, you might be able to just get this to work now: in your profile settings, under Advanced -> Twain Implementation, select "Native Transfer".