Office系列(3)---Office文件(Word、PPT)瘦身

开门见山：在上一篇文章提取Office文件(Word、PPT)中的所有图片 中已经介绍了对特定格式（后缀为.docx、.pptx、.xlsx）Office文件的解析。对于一个Office文件来说，想要减少文件占用的空间大小，最直接的方式就是降低内部引用的资源的大小。最简单的办法，直接对图片进行压缩就可以达到对整个Office文件瘦身的效果。

代码：获取PPT中所有引用到的图片文件，压缩后覆盖掉原文件

using DocumentFormat.OpenXml.Packaging;

/// <summary>
/// PPT文件压缩---压缩图片
/// </summary>
/// <param name="sourcePath">源文件路径</param>
/// <param name="targetDir">目标文件存放目录</param>
/// <returns></returns>
public static void CompressPPTImages(string sourcePath,string targetDir)
{
    using (PresentationDocument presentationDocument = PresentationDocument.Open(filePath, isEditable: true))
    {
        PresentationPart presentationPart = presentationDocument.PresentationPart;
        DocumentFormat.OpenXml.Presentation.Presentation presentation = presentationPart.Presentation;
        List<ImagePart> list = new List<ImagePart>();
        foreach (DocumentFormat.OpenXml.Presentation.SlideId item in presentation.SlideIdList.OfType<DocumentFormat.OpenXml.Presentation.SlideId>())
        {
            SlidePart slidePart = presentationPart.GetPartById(item.RelationshipId) as SlidePart;
            list.AddRange(slidePart.ImageParts);
        }
        List<IGrouping<string, ImagePart>> list2 = list.GroupBy(d => d.Uri.OriginalString).ToList();

        string sFile = Path.Combine( System.Environment.GetEnvironmentVariable("TEMP"), "sfile.tmp");
        string dFile = Path.Combine( System.Environment.GetEnvironmentVariable("TEMP"), "dfile.tmp");
        for (int i = 0; i < list2.Count; i++)
        {
            try
            {
                ImagePart imagePart = list2[i].First();
                using (Stream stream = imagePart.GetStream(FileMode.Open))
                {
                    using (Bitmap bitmap = new Bitmap(stream))
                    {
                        bitmap.Save(sFile);
                    }
                }
                if (CompressImage(sFile, dFile, 40))
                {
                    using (FileStream sourceStream = new FileStream(dFile, FileMode.Open))
                    {
                        imagePart.FeedData(sourceStream);
                    }
                }
            }
            catch (Exception ex)
            {
                LogHelper.Log(ex.Message);
            }
        }
        presentation.Save();

        File.Delete(sFile);
        File.Delete(dFile);
    }
}

图片无损压缩代码

/// <summary>
/// 无损压缩图片
/// </summary>
/// <param name="sFile">原图片地址</param>
/// <param name="dFile">压缩后保存图片地址</param>
/// <param name="flag">压缩质量（数字越小压缩率越高）1-100</param>
/// <param name="size">压缩后图片的最大大小</param>
/// <param name="sfsc">是否是第一次调用</param>
/// <returns></returns>
public static bool CompressImage(string sFile, string dFile, int flag = 90, int size = 300, bool sfsc = true)
{
    //如果是第一次调用，原始图像的大小小于要压缩的大小，则直接复制文件，并且返回true
    FileInfo firstFileInfo = new FileInfo(sFile);
    if (sfsc == true && firstFileInfo.Length < size * 1024)
    {
        firstFileInfo.CopyTo(dFile);
        return true;
    }

    //跳出死循环
    if (sfsc == false && flag <= 0)
    {
        return true;
    }

    Image iSource = Image.FromFile(sFile);
    ImageFormat tFormat = iSource.RawFormat;
    int dHeight = iSource.Height / 2;
    int dWidth = iSource.Width / 2;

    Bitmap ob = new Bitmap(dWidth, dHeight);
    using (Graphics g = Graphics.FromImage(ob))
    {
        g.Clear(Color.WhiteSmoke);
        g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
        g.DrawImage(iSource, new Rectangle(0, 0, dWidth, dHeight), 0, 0, iSource.Width, iSource.Height, GraphicsUnit.Pixel);
    }


    //以下代码为保存图片时，设置压缩质量
    EncoderParameters ep = new EncoderParameters();
    long[] qy = new long[1];
    qy[0] = flag;//设置压缩的比例1-100
    EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);
    ep.Param[0] = eParam;

    try
    {
        ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
        ImageCodecInfo jpegICIinfo = arrayICI.ToList().FirstOrDefault(d => d.FormatDescription.Equals("JPEG"));
        if (jpegICIinfo != null)
        {
            ob.Save(dFile, jpegICIinfo, ep);//dFile是压缩后的新路径
            FileInfo fi = new FileInfo(dFile);
            if (fi.Length > 1024 * size)
            {
                flag = flag - 10;
                CompressImage(sFile, dFile, flag, size, false);
            }
        }
        else
        {
            ob.Save(dFile, tFormat);
        }
        return true;
    }
    catch
    {
        return false;
    }
    finally
    {
        iSource.Dispose();
        ob.Dispose();
    }
}