PdfiumViewer组件扩展(Pdfium.Net.Free)--添加文本

项目地址：

Pdfium.Net：https://github.com/1000374/Pdfium.Net.Free

PdfiumViewer：https://github.com/1000374/PdfiumViewer

Pdfium.Net.Free 支持

• .NETFramework 4.0

• .NETFramework 4.5

• .NETStandard 2.0

• .Net8.0

可以和PdfiumViewer.Free共同使用预览、编辑pdf，也可以直接引用Pdfium.Net.Free 操作pdf，Pdfium.Net.Free封装了现有Pdfium的函数，实现了部分操作pdf的功能，部分功能等待后续~~

Pdfium.Net 添加文本有3个重载 可对添加的文字设置x、y坐标、字体大小、颜色、x、y缩放比例、旋转、裁切、混合模式、渲染模式（根据此设置镂空样式

FpdfTextRenderMode.STROKE_CLIP）、镂空填充色、镂空颜色。当strokeColor为null时 取fillColor

1.当前重载使用pdf标准字库添加文字（中文会乱码）

    /// <summary>
    /// Add text object using one of the standard PDF fonts.  Chinese maybe garbled characters
    /// </summary>
    /// <param name="text"></param>
    /// <param name="posX"></param>
    /// <param name="posY"></param>
    /// <param name="font_size">the font size for the new text object.</param>
    /// <param name="fillColor"></param>
    /// <param name="fontName"><see cref="Native.Enums.StandardPDFFonts"/></param>
    /// <param name="scalex"></param>
    /// <param name="scaley"></param>
    /// <param name="rotate"></param>
    /// <param name="shear"></param>
    /// <param name="blend">Blend mode can be one of following: Color, ColorBurn, ColorDodge, Darken,Difference, Exclusion, HardLight, Hue, Lighten, Luminosity, Multiply, Normal,Overlay, Saturation, Screen, SoftLight.<see cref="BlendMode"/></param>
    /// <param name="render_mode">render_mode<see cref="FpdfTextRenderMode"/></param>
    /// <param name="strokeColor">stroke Color render_mode </param>
    /// <param name="strokeWidth">stroke Width</param>
    /// <returns></returns>
    public bool AddString(string text, int posX, int posY, float font_size, Color fillColor, string fontName, float scalex = 1f, float scaley = 1, float rotate = 0, float shear = 0, 
string blend = BlendMode.Darken, FpdfTextRenderMode render_mode = FpdfTextRenderMode.FILL, Color? strokeColor = null, float strokeWidth = 0.2f)

 

调用示例：

  using (var doc = PdfDocument.CreateNew())
  {
      var cSharpString = "!you ok 这是第一句。 这是第二行。a you ok";
      var page = doc.Pages.Add(612, 792);
      page.AddString(cSharpString, 10, 50, 12, Color.Black, StandardPDFFonts.TimesNewRoman);
      doc.Save("./Pdfium.NetTests/AddString1.pdf");
  }

　　

2.当前重载使用获取的PdfFont 对象添加文字，详情请参照

Pdfium.Net.Free 一个免费的Pdfium的 .net包装器--加载字体 

   /// <summary>
   /// add Text with add <see cref="FpdfFontT"/>
   /// </summary>
   /// <param name="pageNumber"></param>
   /// <param name="text"></param>
   /// <param name="posX"></param>
   /// <param name="posY"></param>
   /// <param name="font_size"></param>
   /// <param name="fillColor"></param>
   /// <param name="font"></param>
   /// <param name="scalex"></param>
   /// <param name="scaley"></param>
   /// <param name="rotate"></param>
   /// <param name="shear"></param>
   /// <param name="blend">Blend mode can be one of following: Color, ColorBurn, ColorDodge, Darken,Difference, Exclusion, HardLight, Hue, Lighten, Luminosity, Multiply, Normal,Overlay, Saturation, Screen, SoftLight.<see cref="BlendMode"/></param>
   /// <param name="render_mode">render_mode<see cref="FpdfTextRenderMode"/></param>
   /// <param name="strokeColor">stroke Color render_mode </param>
   /// <param name="strokeWidth">stroke Width</param>
   /// <returns></returns>
   public bool AddString(string text, float posX, float posY, float font_size, Color fillColor, PdfFont font, float scalex = 1f, float scaley = 1, float rotate = 0, float shear = 0, string blend = BlendMode.Darken,
 FpdfTextRenderMode render_mode = FpdfTextRenderMode.FILL, Color? strokeColor = null, float strokeWidth = 0.2f)

　

调用示例（从pdf中获取字体后写入）：

   var pathPdf = "./Pdfium.NetTests/resources/fontText.pdf";
   using (var doc = PdfDocument.Load(new MemoryStream(File.ReadAllBytes(pathPdf))))
   {
       var font = doc.Pages[0].GetTextObjFont("你", out float size);
       if (!font.IsNull)
       {
           var emb = font.IsEmbedded;
           var cSharpString = "你好啊,abc";
           var page = doc.Pages[0];
           page.AddString(cSharpString, 10, 50, size, Color.Black, font);
           doc.Save("./Pdfium.NetTests/TextObjFont.pdf");
       }
   }

　　

3.当前重载需提前调用

   public void LoadFont(string fontPath, bool isSubSet = false, string words = null, FpdfFontTypes fontTypes = FpdfFontTypes.TrueType)

　　

方法，且只能调用一次，否则抛出找不到字体对象，或者pdf会多次加载字体导致pdf很大，也就是每次调用都会往doc中加载一次字库。

可创建子集后加载字库，以减少pdf大小，具体参照

Pdfium.Net.Free 一个免费的Pdfium的 .net包装器--创建字符子集 

 /// <summary>
 /// add Text with add <see cref="FpdfFontT"/>
 /// </summary>
 /// <param name="text"></param>
 /// <param name="posX"></param>
 /// <param name="posY"></param>
 /// <param name="font_size">the font size for the new text object.</param>
 /// <param name="fillColor">the font color.</param>
 /// <param name="isSubSet">ttf path use File.ReadAllBytes(fontPath);</param>
 /// <param name="scalex">scale x</param>
 /// <param name="scaley">scale y</param>
 /// <param name="rotate">rotate</param>
 /// <param name="shear">shear</param>
 /// <param name="blend">Blend mode can be one of following: Color, ColorBurn, ColorDodge, Darken,Difference, Exclusion, HardLight, Hue, Lighten, Luminosity, Multiply, Normal,Overlay, Saturation, Screen, SoftLight.<see cref="BlendMode"/></param>
 /// <param name="render_mode">render_mode<see cref="FpdfTextRenderMode"/></param>
 /// <param name="strokeColor">stroke Color render_mode </param>
 /// <param name="strokeWidth">stroke Width</param>
 /// <returns></returns>
 public bool AddString(string text, float posX, float posY, float font_size, Color fillColor, float scalex = 1f, float scaley = 1, float rotate = 0, float shear = 0,  
string blend = BlendMode.Darken, FpdfTextRenderMode render_mode = FpdfTextRenderMode.FILL, Color? strokeColor = null, float strokeWidth = 0.2f)

　

调用字符集全部加载示例：

　

  using (var doc = PdfDocument.CreateNew())
  {
      var fontPath = @"c:\Windows\fonts\simhei.ttf";
      doc.LoadFont(fontPath);
      var cSharpString = "!you ok 这是第一句。 这是第二行。a you ok";
      var page = doc.Pages.Add(612, 792);
      page.AddString(cSharpString, 10, 50, 12, Color.Black);
      doc.Save("./Pdfium.NetTests/AddString.pdf");
  }

　　

创建字符子集加载示例：

 using (var doc = PdfDocument.CreateNew())
 {
     var fontPath = @"c:\Windows\fonts\simhei.ttf";

     var cSharpString = "!you ok 这是第一句。";
     var cSharpString2 = " 这是第二行。a you ok 你好 abcdefghijklmnopqrstuvwxyz1234567890-*/+~`@#$%^&*(){}[];:'|?,，。.！!";
     doc.LoadFont(fontPath, true, cSharpString + cSharpString2);
     var page = doc.Pages.Add(612, 792);
     page.AddString(cSharpString, 10, 50, 12, Color.Black);

     page.AddString(cSharpString2, 10, 80, 12, Color.Black);
     doc.Save("./Pdfium.NetTests/AddString3.pdf");
 }