将图像转换为流以进行即时处理

Question

所以我使用 SharpZipLib 递归浏览我的文档并打包它找到的任何 JPEG 图像，如下所示：

foreach (string filename in filenames)
{
    string[] file_split = filename.Split('.');
    if (file_split[file_split.Count() - 1].Equals("jpg"))
    {
        // You might replace these 3 lines with your own stream code
        ScaleImage scaleImage = new ScaleImage();
        FileStream file = new FileStream("path to file", FileMode.Open);

        using (Stream inputStream = File.OpenRead(filename))
        {
            string tarName = filename.Substring(3); // strip off "C:\"
            Image tmpImg = scaleImage.scale(tmpImg);

            long fileSize = inputStream.Length;

            // Create a tar entry named as appropriate. You can set the name to anything,
            // but avoid names starting with drive or UNC
            TarEntry entry = TarEntry.CreateTarEntry(tarName);

            // Must set size, otherwise TarOutputStream will fail when output exceeds.
            entry.Size = fileSize;

            // Add the entry to the tar stream, before writing the data.
            tarOutputStream.PutNextEntry(entry);

            // this is copied from TarArchive.WriteEntryCore
            byte[] localBuffer = new byte[32 * 1024];
            while (true)
            {
                int numRead = inputStream.Read(localBuffer, 0, localBuffer.Length);
                if (numRead <= 0)
                {
                    break;
                }
                tarOutputStream.Write(localBuffer, 0, numRead);
            }
        }
        tarOutputStream.CloseEntry();
    }
}

// Recurse. Delete this if unwanted.
string[] directories = Directory.GetDirectories(sourceDirectory);
foreach (string directory in directories)
{
    CreateTarManually(tarOutputStream, directory);
}

为了尽可能地减少 tar 大小 - 我试图在从流中读取图像时将所有图像调整为指定的宽度 x 高度 "on the fly"。我想我可以在它进入 using (Stream inputStream) 部分后从流中加载图像，并从那里使用找到的调整图像大小的函数。像这样：

public Bitmap scale(Image oldImage)
{
    double resizeFactor = 1;
    if (oldImage.Width > 150 || oldImage.Height > 150)
    {
        double widthFactor = Convert.ToDouble(oldImage.Width) / 150;
        double heightFactor = Convert.ToDouble(oldImage.Height) / 150;
        resizeFactor = Math.Max(widthFactor, heightFactor);
    }
    int width = Convert.ToInt32(oldImage.Width / resizeFactor);
    int height = Convert.ToInt32(oldImage.Height / resizeFactor);
    Bitmap newImage = new Bitmap(width, height);
    Graphics g = Graphics.FromImage(newImage);
    g.InterpolationMode =  System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
    g.DrawImage(oldImage, 0, 0, newImage.Width, newImage.Height);
    return newImage;
}

我的问题是，如何传递要调整大小的流对象，然后将流 object/resized 对象添加到 tar 文件，而不是原始文件本身？实际上，我希望所有这些都在内存中完成，以节省在调整磁盘大小时复制磁盘上的每个文件

Answer 1

将使用 here 的答案。

public Stream ImageToStream(Image image)
{
    //Save to stream
    MemoryStream stream = new MemoryStream();
    image.Save(stream, ImageFormat.Jpeg);
    stream.Seek(0, SeekOrigin.Begin); //Need to reset position to 0
    return stream;
}

并且不使用文件中的输入流，而是使用函数中的输入流：

Image oldImage = Image.FromFile(fileName);
Image newImage = scale(oldImage);
Stream inputStream = ImageToStream(newImage);

奖金建议：

如果要检查文件扩展名，可以这样使用Path.GetExtension(fileName)：

var fileExtension = Path.GetExtension(filename);
if (fileExtension.Equals(".jpg"))
{
     //ApplyLogic
}

将图像转换为流以进行即时处理

Converting images into Streams for on the fly processing

c#

.net

image

stream

sharpziplib