HttpPostedFileBase调整图像大小

Question

I have the following line of code which takes my HttpPostedFileBase and converts it to an image.

I have messed around with Encoder Parameteres to try and resize the image but can't seem to do this.

What is the best way to resize the image to 250x250?

I would also prefer it to take the middle of the image as 250x250 rectangle rather than somewhere random.

What is the most space efficent way to convert and save the image as it will be going in the database?

Please note that model.Image is of type HttpPostedFileBase .

var image = Image.FromStream(model.Image.InputStream, true, true);

ImageCodecInfo jpgInfo = ImageCodecInfo.GetImageEncoders()
    .Where(codecInfo => codecInfo.MimeType == "image/jpeg").First();
using (EncoderParameters encParams = new EncoderParameters(1))
{
    encParams.Param[0] = new EncoderParameter(Encoder.Quality, (long)50);

    //quality should be in the range [0..100]
    using (var ms = new MemoryStream())
    {
        // Convert Image to byte[]
        image.Save(ms, ImageFormat.Jpeg);
        byte[] imageBytes = ms.ToArray();

        // Convert byte[] to Base64 String
        string base64String = Convert.ToBase64String(imageBytes);
        image64 = base64String;
    }
}

Answer 1

The best way is to use an established library like ImageResizer ; that way, you avoid re-inventing the wheel. If you are concerned about space efficiency (file size), use the JPEG format with maximum compression. Note that using JPEG's lossy encoding will drastically reduce image quality. If you want to use a lossless encoding, try PNG. Compressing PNG images is quite difficult in .NET, in my experience. I searched in vain awhile back for a single library that would do it and all I found were thick-client Windows applications.