Csharp 将图像字节数组转换为 PDF

I suppose what you want is the PdfWriter to auto-scale the Image inside the Document.
Optionally, position the Image in the center of the Page.

您可以更改代码设置[Image].SetAutoScale(true)和[Image].SetHorizontalAlignment(HorizontalAlignment.CENTER):

Note:我为iText.Layout.Properties(别名:PdfProperties)和iText.Layout.Element.Image(别名:PdfImage)定义了别名，以避免与其他别名冲突.Net程序集，这些程序集的类和枚举数具有相同的确切名称.只要把它们取下来，以防你根本不需要它们.

using iText.IO.Image;
using iText.Kernel.Pdf;
using iText.Layout;
using PdfProperties = iText.Layout.Properties;
using PdfImage = iText.Layout.Element.Image;

public byte[] ConvertImageToPDF(byte[] imageBytes)
{
    using (var ms = new MemoryStream()) {
        using (var pdfWriter = new PdfWriter(ms)) {
            var pdf = new PdfDocument(pdfWriter);
            var document = new Document(pdf);

            var img = new PdfImage(ImageDataFactory.Create(imageBytes))
                .SetAutoScale(true)
                .SetHorizontalAlignment(PdfProperties.HorizontalAlignment.CENTER);

            document.Add(img);
            document.Close();
            pdf.Close();
            return ms.ToArray();
        }
    }
}

You can also specify the size, in floating point units, of the Image and use the [Image].ScaleToFit() method, to scale the Image within those bounds.
Here, using a PageSize set to PageSize.A4. You can of course set different measures.

using iText.Kernel.Geom;

// [...]
var document = new Document(pdf);

var page = document.GetPageEffectiveArea(PageSize.A4);
var img = new PdfImage(ImageDataFactory.Create(imageBytes))
    .ScaleToFit(page.GetWidth(), page.GetHeight())
    .SetHorizontalAlignment(PdfProperties.HorizontalAlignment.CENTER);

// [...]