.NET保存的JPEG具有相同的质量，因为它被加载 [英] .NET Saving jpeg with the same quality as it was loaded

问题描述

我有一门大炮数码相机，我把它拍照与超细质量和它输出.jpg文件的大小300万。
如果我加载像这样在ASP.NET（这是非常有用的改变它的dpi分辨率或裁剪或whaterver）

I have a cannon digital camera and I set it to take pictures with superfine quality and it outputs a .jpg file 3 mega in size. If I load it like this in ASP.NET(this is useful to change it's dpi resolution or crop it or whaterver)

imgPicture = Image.FromFile(Config.WorkDirectory + this.TempPhotoName);
bmpPicture = new Bitmap(imgPicture);

然后我再保存它是这样的：

and then I save it again like this:

bmpModified.Save(Config.WorkDirectory + this.TempPhotoName,System.Drawing.Imaging.ImageFormat.Jpeg);

它输出JPG格式，这只是700KB左右的规模。有质量的损失。

it outputs a jpg that is only 700KB or so in size. There is a loss of quality.

我也试过保存这样的：

bmpPicture.Save(Config.WorkDirectory + this.TempPhotoName, codecJpeg, encparams);

其中codecJpeg是

where codecJpeg is

ImageCodecInfo codecJpeg = this.getEncoderInfo("image/jpeg");


    private ImageCodecInfo getEncoderInfo(string mimeType)
    {
        // Get image codecs for all image formats
        ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();

        // Find the correct image codec
        for (int i = 0; i < codecs.Length; i++)
            if (codecs[i].MimeType == mimeType)
                return codecs[i];
        return null;
    }

和encparams：

and encparams:

EncoderParameters encparams = new EncoderParameters(1);
encparams.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 97L);

这样的大小（我怀疑也是质量）保持，但我输入查询用手质量。

This way the size(and I suspect also the quality) is maintained but I am inputing the quality by hand.

我要问：

有没有办法将图像具有相同的品质保存，因为它是没有硬编码的质量值装？

Is there a way to save the image with the same quality as it was loaded without hardcoding the quality value?

感谢您提前

推荐答案

因此​​，它听起来就像你知道如何设置的质量，你真的只需要知道如何的从原来的取的质量形象？

So it sounds like you know how to set the quality, you really just need to know how to fetch the quality from the original image?

我怀疑 图片.PropertyItems 是你的朋友，如果质量在开始与元数据。 （我不知道是否有甚至在JPEG品质连接codeRS标准等级。）

I suspect that Image.PropertyItems is your friend, if the quality is in the metadata to start with. (I don't know if there's even a standard scale for quality within JPEG encoders.)

编辑：我刚刚查，和JPEG我下载没有任何标签的质量

I've just checked, and a jpeg I downloaded didn't have any tags for quality.

一个选择可能是摸出文件应该有多大最终有大致相同的质量，然后保存了好几次，做一个二进制搜索制定出最合适的品质。过甜的，但它可能只是工作。

One option might be to work out how big the file should end up to have roughly the same quality, and then save it several times, doing a binary search to work out the most appropriate quality. Icky, but it might just work.

我暗自怀疑存在的不是的一个办法只有preserve原来的画质设置，虽然我没有很好的理由，这种怀疑...

I have a sneaking suspicion that there isn't a way to just preserve the original quality setting, although I don't have very good grounds for that suspicion...

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