src/PdfEncoder.Infrastructure/Pdf/PdfPageRenderer.cs - master - afanasevn/PdfEncoder

src/PdfEncoder.Infrastructure/Pdf/PdfPageRenderer.cs
71 строка2 KB
IBS\NAfanasev
DocumentContext local functional
01 июл 2026, 15:30
01 июл 2026, 15:30b4038c9
using Docnet.Core.Models;
using PdfEncoder.Application.Abstractions;
using UglyToad.PdfPig;

namespace PdfEncoder.Infrastructure.Pdf;

/// <summary>
/// Рендер страниц PDF через Docnet.
/// </summary>
public sealed class PdfPageRenderer(IDocLibProvider docLibProvider) : IPdfPageRenderer
{
    /// <inheritdoc />
    public Task<RenderedPageImage> RenderPageAsync(
        ReadOnlyMemory<byte> content,
        int pageIndex,
        int dpi,
        CancellationToken ct)
    {
        ct.ThrowIfCancellationRequested();

        var dimensions = ResolvePageDimensions(content, pageIndex, dpi);
        using var reader = docLibProvider.Instance.GetDocReader(content.ToArray(), dimensions);
        using var pageReader = reader.GetPageReader(pageIndex);

        var width = pageReader.GetPageWidth();
        var height = pageReader.GetPageHeight();
        var bgra = pageReader.GetImage();
        var grayscale = ConvertBgraToGrayscale(bgra);

        return Task.FromResult(new RenderedPageImage
        {
            GrayscaleBytes = grayscale,
            Width = width,
            Height = height
        });
    }

    private static PageDimensions ResolvePageDimensions(
        ReadOnlyMemory<byte> content,
        int pageIndex,
        int dpi)
    {
        using var document = PdfDocument.Open(content);
        var pageNumber = pageIndex + 1;
        if (pageNumber < 1 || pageNumber > document.NumberOfPages)
        {
            return new PageDimensions(1700, 2200);
        }

        var page = document.GetPage(pageNumber);
        var widthPx = Math.Max(1, (int)Math.Round(page.Width / 72d * dpi));
        var heightPx = Math.Max(1, (int)Math.Round(page.Height / 72d * dpi));
        return new PageDimensions(widthPx, heightPx);
    }

    private static byte[] ConvertBgraToGrayscale(byte[] bgra)
    {
        var pixelCount = bgra.Length / 4;
        var grayscale = new byte[pixelCount];
        for (var i = 0; i < pixelCount; i++)
        {
            var offset = i * 4;
            var b = bgra[offset];
            var g = bgra[offset + 1];
            var r = bgra[offset + 2];
            grayscale[i] = (byte)((r * 299 + g * 587 + b * 114) / 1000);
        }

        return grayscale;
    }
}