PDFsharp Ximage 不包含包含 1 个参数的构造函数

Question

我正在尝试编写一个 XImage 函数，它从给定的 URL 中读取图像，它看起来像：

    public static XImage FromURI(string uri)
    {
        HttpWebRequest webRequest = (HttpWebRequest)HttpWebRequest.Create(uri);
        webRequest.AllowWriteStreamBuffering = true;
        WebResponse webResponse = webRequest.GetResponse();
        System.Drawing.Image image = System.Drawing.Image.FromStream(webResponse.GetResponseStream());
        webResponse.Close();
        PdfSharp.Drawing.XImage ximg = new PdfSharp.Drawing.XImage(image);
        return new PdfSharp.Drawing.XImage(image);
    }

但我在行

上收到错误

        return new PdfSharp.Drawing.XImage(image);

它说：

XImage does not contain a constructor that contains 1 argument.

当我查看 XImage.cs 文件时，它似乎有一个包含 1 个参数的构造函数。

namespace PdfSharp.Drawing
{
    //
    // Summary:
    //     Defines an object used to draw image files (bmp, png, jpeg, gif) and PDF forms.
    //     An abstract base class that provides functionality for the Bitmap and Metafile
    //     descended classes.
    public class XImage : IDisposable
    {
        //
        // Summary:
        //     Initializes a new instance of the PdfSharp.Drawing.XImage class.
        protected XImage();

        //
        // Summary:
        //     Gets the vertical resolution of the image.
        public virtual double VerticalResolution { get; }
        //
        // Summary:
        //     Gets the horizontal resolution of the image.
        public virtual double HorizontalResolution { get; }
        //
        // Summary:
        //     Gets the size in point of the image.
        public virtual XSize Size { get; }
        //
        // Summary:
        //     Gets the height of the image in pixels.
        public virtual int PixelHeight { get; }
        //
        // Summary:
        //     Gets the width of the image in pixels.
        public virtual int PixelWidth { get; }
        //
        // Summary:
        //     Gets the height of the image in point.
        public virtual double PointHeight { get; }
        //
        // Summary:
        //     Gets the width of the image in point.
        public virtual double PointWidth { get; }
        //
        // Summary:
        //     Gets the height of the image.
        [Obsolete("Use either PixelHeight or PointHeight. Temporarily obsolete because of rearrangements for WPF. Currently same as PixelHeight, but will become PointHeight in future releases of PDFsharp.")]
        public virtual double Height { get; }
        //
        // Summary:
        //     Gets the width of the image.
        [Obsolete("Use either PixelWidth or PointWidth. Temporarily obsolete because of rearrangements for WPF. Currently same as PixelWidth, but will become PointWidth in future releases of PDFsharp.")]
        public virtual double Width { get; }
        //
        // Summary:
        //     Gets or sets a flag indicating whether image interpolation is to be performed.
        public virtual bool Interpolate { get; set; }
        //
        // Summary:
        //     Gets the format of the image.
        public XImageFormat Format { get; }

        //
        // Summary:
        //     Tests if a file exist. Supports PDF files with page number suffix.
        //
        // Parameters:
        //   path:
        //     The path to a BMP, PNG, GIF, JPEG, TIFF, or PDF file.
        public static bool ExistsFile(string path);
        //
        // Summary:
        //     Creates an image from the specified file.
        //
        // Parameters:
        //   path:
        //     The path to a BMP, PNG, GIF, JPEG, TIFF, or PDF file.
        public static XImage FromFile(string path);
        //
        // Summary:
        //     Conversion from Image to XImage.
        public static XImage FromGdiPlusImage(Image image);
        //
        // Summary:
        //     Under construction
        public void Dispose();
        //
        // Summary:
        //     Disposes underlying GDI+ object.
        protected virtual void Dispose(bool disposing);

        //
        // Summary:
        //     Implicit conversion from Image to XImage.
        public static implicit operator XImage(Image image);
    }
}

即使我尝试修复此文件，也无法修复，因为它有一个 [来自元数据] 标签。

Answer 1

class 中的最后一行是隐式运算符，而不是构造函数。这将隐式地将 Image 转换为 XImage，即没有任何数据丢失。您不能像以前那样从 Image 创建 XImage。你需要这样做：

 XImage xImage = new PdfSharp.Drawing.XImage();
 xImage = image;
 return xImage;

您可以阅读有关 implice https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/implicit

Answer 2

您能做的最好的事情是：跳过创建 Image 并直接从流创建 XImage。

XImage class 有一些静态成员。有 XImage.FromGdiImage 需要一个 Image （这将是你问题的答案）并且有 XImage.FromStream 避免首先创建 Image。

当您的项目引用 PDFsharp DLL（例如来自 NuGet）时，Visual Studio 将向您显示无法更改的反编译元数据。您可以使用 PDFsharp 源代码，添加对 .csproj 文件的引用并根据需要进行更改。
以 Image 作为参数的构造函数不是 public。无需将其设置为 public，因为您可以使用 XImage.FromGdiImage 来访问它。请注意，只有 PDFsharp 的 GDI 构建具有此方法。使用 WPF 构建时，可以使用 XImage.FromStream.

PDFsharp Ximage 不包含包含 1 个参数的构造函数

PDFsharp Ximage does not contain a constructor that contains 1 argument

c#

image

pdfsharp