C# pdf转png图片

写作背景

最近有朋友问我有没有pdf转jpg或者png的工具，发他一个，网上查了好多资料最后发现大部分都是收费项目。好在咱是程序员，没有咱就手动免费撸一个。最后实现了完美转换。

开发工具：vs2019
.netframework版本:4.5.2
程序依赖项:

<?xml version="1.0" encoding="utf-8"?>
<packages>
  <package id="PdfiumViewer" version="2.13.0.0" targetFramework="net452" />
  <package id="PdfiumViewer.Native.x86.v8-xfa" version="2018.4.8.256" targetFramework="net452" />
</packages>

程序代码

using PdfiumViewer;
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
 
namespace PdfConverter
{
    class Program
    {
        static void Main(string[] args)
        {
            var path = AppDomain.CurrentDomain.BaseDirectory ;
            var helper = new PdfHelper();
            helper.PdfToPic(path + "input\\1.pdf", path + "output\\", ImageFormat.Png);
            Console.WriteLine("转换完成.");
        }
    }
 
    class PdfHelper
    {
        /// <summary>
        /// <param name="filePath">pdf文件路径</param> 
        /// <param name="outFilePath">picture输出文件路径</param> 
        /// <param name="image">文件格式：Jpeg  （转换后文件格式，如：Jpeg，Png等）</param> 
        /// </summary> 
        public void PdfToPic(string filePath, string outFilePath, ImageFormat image)
        {
            var pdf = PdfDocument.Load(filePath);
            var pdfpage = pdf.PageCount;
            var pagesizes = pdf.PageSizes;
            outFilePath = $"{outFilePath}\\{DateTime.Now.ToString("yyyyMMdd-HHmmss")}";
            for (int i = 1; i <= pdfpage; i++)
            {
                Size size = new Size();
                size.Height = (int)pagesizes[(i - 1)].Height;
                size.Width = (int)pagesizes[(i - 1)].Width;
                //可以把".jpg"写成其他形式 RenderPage(filePath, i, size, picPath); 
                string outFile = $"{outFilePath}({i}).{image}";
                RenderPage(filePath, i, size, outFile, image);
            }
 
        }
        /// <summary>
        /// 渲染图片
        /// </summary>
        /// <param name="pdfPath"></param>
        /// <param name="pageNumber"></param>
        /// <param name="size"></param>
        /// <param name="outputPath"></param>
        /// <param name="mat"></param>
        /// <param name="dpi"></param>
        private void RenderPage(string pdfPath, int pageNumber, System.Drawing.Size size, string outputPath, ImageFormat mat, int dpi = 300)
        {
            using (var document = PdfDocument.Load(pdfPath))
            using (var stream = new FileStream(outputPath, FileMode.Create))
            using (var image = GetPageImage(pageNumber, size, document, dpi))
                image.Save(stream, mat);
        }
        /// <summary>
        /// 根据页数转换图片
        /// </summary>
        /// <param name="pageNumber"></param>
        /// <param name="size"></param>
        /// <param name="document"></param>
        /// <param name="dpi"></param>
        /// <returns></returns>
        private static System.Drawing.Image GetPageImage(int pageNumber, Size size, PdfDocument document, int dpi)
        {
            return document.Render(pageNumber - 1, size.Width, size.Height, dpi, dpi, PdfRenderFlags.CorrectFromDpi);
        }
 
    }
}
 

注释：

• PdfRenderFlags.Annotations：设置是否要渲染注释
• PdfRenderFlags.CorrectFromDpi：DPI的正确高度/宽度。更正DPI=8192
• 参数都设置为：PdfRenderFlags.CorrectFromDpi转换picture文件像素就是最合适的了。