Deskew 准确性: .NET 和 Aspose.Imaging

using System;
using System.IO;
using Aspose.Imaging;
using Aspose.Imaging.FileFormats.Tiff;
using Aspose.Imaging.ImageOptions;

class Program
{
    static int Main(string[] args)
    {
        if (args.Length < 2)
        {
            Console.WriteLine("Usage: dotnet run -- <inputImageOrTiff> <outputImageOrTiff>");
            return 1;
        }

        string inputPath  = args[0];
        string outputPath = args[1];

        try
        {
            using (var image = Image.Load(inputPath))
            {
                // Multi-page TIFF? Deskew frame-by-frame.
                if (image is TiffImage tiff)
                {
                    foreach (var frame in tiff.Frames)
                    {
                        // --- Optional: lightweight preprocessing for better angle detection ---
                        // Convert to grayscale-like statistics to reduce chroma noise.
                        // Many real scans already are gray/bilevel; if not, Normalize() helps.
                        TryNormalizeForDeskew(frame);

                        // --- Deskew ---
                        // true  = expand canvas to avoid cropping
                        // White = fill color for the new corners created by rotation
                        frame.NormalizeAngle(true, Aspose.Imaging.Color.White);
                    }

                    tiff.Save(outputPath); // encoder inferred from extension
                }
                else
                {
                    // Single-page raster image
                    var raster = image as RasterImage 
                                 ?? throw new InvalidOperationException("Input is not a raster image.");

                    TryNormalizeForDeskew(raster);
                    raster.NormalizeAngle(true, Aspose.Imaging.Color.White);

                    // Choose encoder explicitly (e.g., PNG/JPEG/TIFF). Here we mirror input extension.
                    image.Save(outputPath);
                }
            }

            Console.WriteLine($"✅ Deskew complete: {Path.GetFullPath(outputPath)}");
            return 0;
        }
        catch (Exception ex)
        {
            Console.Error.WriteLine("❌ " + ex.Message);
            return 2;
        }
    }

    /// <summary>
    /// Minimal, safe preprocessing to stabilize skew detection.
    /// Avoid heavy blurs that can smear thin text.
    /// </summary>
    private static void TryNormalizeForDeskew(RasterImage raster)
    {
        // Ensure pixels are accessible (performance hint for subsequent operations).
        raster.CacheData();

        // If the image has wildly varying brightness (camera shots), a light contrast
        // normalization can help align text lines for skew detection. The exact set
        // of helpers varies by version; keep it simple and non-destructive.
        //
        // Tip: If your version exposes BinarizeOtsu/AdaptiveBinarize, try them
        // *after* deskew for OCR workflows to preserve thin strokes.

        // Example: If available in your build, uncomment one of these:
        // raster.AdjustBrightnessContrast(brightness: 0, contrast: 10); // gentle contrast pop
        // raster.Grayscale(); // reduce chroma noise if present

        // Leave as-is if your scans are already clean (e.g., 300 dpi monochrome).
    }
}