client/Services/Printing/ImagePrintJobExecutor.cs

using CloudPrint.Client.Models;
using System.Drawing;
using System.Drawing.Printing;
using System.IO;

namespace CloudPrint.Client.Services.Printing;

public sealed class ImagePrintJobExecutor : IPrintJobExecutor
{
    private readonly IWindowsPrintQueueService _queueService;

    private static readonly HashSet<string> SupportedExtensions = new(StringComparer.OrdinalIgnoreCase)
    {
        ".jpg", ".jpeg", ".png", ".bmp", ".gif"
    };

    public ImagePrintJobExecutor(IWindowsPrintQueueService queueService)
    {
        _queueService = queueService;
    }

    public bool CanHandle(PrintJob job)
    {
        return SupportedExtensions.Contains(Path.GetExtension(job.FilePath));
    }

    public Task ExecuteAsync(PrintJob job, IProgress<int>? progress, CancellationToken cancellationToken = default)
    {
        PrintFileGuards.EnsurePrintableFile(job);

        return Task.Run(() =>
        {
            cancellationToken.ThrowIfCancellationRequested();
            using var image = Image.FromFile(job.FilePath);
            using var document = new PrintDocument
            {
                DocumentName = string.IsNullOrWhiteSpace(job.FileName) ? job.JobNo : job.FileName,
                PrinterSettings =
                {
                    PrinterName = job.PrinterName,
                    Copies = (short)Math.Clamp(job.Copies, 1, short.MaxValue)
                }
            };

            if (document.PrinterSettings.CanDuplex)
            {
                document.PrinterSettings.Duplex = job.Duplex ? Duplex.Vertical : Duplex.Simplex;
            }

            document.DefaultPageSettings.Color = job.Color;
            document.PrintPage += (_, args) => DrawImageToPage(image, args);
            progress?.Report(20);
            document.Print();
            CaptureWindowsJob(job, document.DocumentName);
            progress?.Report(100);
        }, cancellationToken);
    }

    private void CaptureWindowsJob(PrintJob job, string documentName)
    {
        var queueJob = _queueService.FindLatestJob(job.PrinterName, documentName);
        if (queueJob is null)
        {
            return;
        }

        job.WindowsJobId = queueJob.JobId;
        job.WindowsJobStatus = queueJob.Status;
    }

    private static void DrawImageToPage(Image image, PrintPageEventArgs args)
    {
        if (args.Graphics is null)
        {
            throw new InvalidOperationException("打印图形上下文不可用");
        }

        var bounds = args.MarginBounds;
        var ratio = Math.Min(bounds.Width / (double)image.Width, bounds.Height / (double)image.Height);
        var width = (int)(image.Width * ratio);
        var height = (int)(image.Height * ratio);
        var x = bounds.Left + (bounds.Width - width) / 2;
        var y = bounds.Top + (bounds.Height - height) / 2;

        args.Graphics.DrawImage(image, x, y, width, height);
        args.HasMorePages = false;
    }
}