压缩图像而不保存

问题描述

我正在使用以下代码来压缩图像，这做得很好，但是我想使用压缩后的图像而不保存它。因此，现在我必须保存图像，然后再次读取它，这很慢。

I am using the following code to compress an image and it does a nice job but I want to use the compressed image not save it. So right now I have to save the image then read it in again which is slow. Is there a way of compressing it with out saving it.

    private void compress(System.Drawing.Image img, long quality, ImageCodecInfo codec)
    {
        EncoderParameters parameters = new EncoderParameters(1);
        parameters.Param[0] = new EncoderParameter(Encoder.Quality, quality);
        img.Save("check1.jpg", codec, parameters);
    }

    private static ImageCodecInfo GetCodecInfo(string mimeType)
    {
        foreach (ImageCodecInfo encoder in ImageCodecInfo.GetImageEncoders())
            if (encoder.MimeType == mimeType)
                return encoder;
        throw new ArgumentOutOfRangeException(
            string.Format("'{0}' not supported", mimeType));
    }

推荐答案

有一个，因此您可以将其直接保存到 MemoryStream ，而无需保存到磁盘/重新加载。

There is an overload that takes a Stream so you can save it straight to a MemoryStream and won't need to save to disk/reload.

EncoderParameters parameters = new EncoderParameters(1);
parameters.Param[0] = new EncoderParameter(Encoder.Quality, quality);

var ms = new MemoryStream();
img.Save(ms, codec, parameters);

//Do whatever you need to do with the image
//e.g.
img = Image.FromStream(ms);

在注释中提到参数无效异常的原因是因为在尝试调用 FromStream 之前不会处理图像，因此您需要对其进行处理。另外，我不知道您如何调用此方法，但您可能应该对其进行更新以返回 MemoryStream 。

The reason you're getting the "Parameter not valid" exception you mention in the comments is because the image isn't being disposed of before you try to call FromStream, so you'll need to dispose it. Also, I don't know how you're calling this method, but you should probably update it to return the MemoryStream.

private void compress(System.Drawing.Image img, long quality, ImageCodecInfo codec)
{
    EncoderParameters parameters = new EncoderParameters(1);
    parameters.Param[0] = new EncoderParameter(Encoder.Quality, quality);

    var ms = new MemoryStream();
    img.Save(ms, codec, parameters);
    return ms;
}

public void MyMethod()
{
    MemoryStream ms;
    using(var img = Image.FromFile("myfilepath.img"))
    {
        ms = compress(img, /*quality*/, /*codec*/);
    }

    using(var compressedImage = Image.FromStream(ms))
    {
        //Use compressedImage
    }
}

注意我如何从压缩返回 ms 。另外，更重要的是，我们如何将初始 img 包裹在 using 语句中，这将正确处理文件句柄，以及之后被处理掉后，创建第二个 compressedImage ，它也在中使用，因此它将完成操作后， 也将得到适当处理。

Notice how I return ms from compress and capture it. Also, more importantly, how we wrap the initial img in a using statement which will dispose the file handle correctly, and after that gets disposed create the second compressedImage which is also in a using so it will also get disposed of properly when you're done.

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