Render image to the screen from MVC controller

问题

I have images in the database and I want to return the image for viewing from an action. Here's my action.

public FileContentResult Index(ItemImageRequest request)
{
    var result = queueService.GetItemImage(request);

    if (result.TotalResults == 0)
        return File(new byte[0], "image/jpeg");

    var image = result.FirstResult;

    return File(image.Image, "image/tif");
}

I have also tried this code

public FileStreamResult Index(ItemImageRequest request)
{
    //retrieval omitted

    var image = result.FirstResult;

    System.IO.Stream stream = new System.IO.MemoryStream(image.Image);

    return new FileStreamResult(stream, "image/tif");
}

When I go to my action in the browser it prompts me for download. I don't want it to download, I want it to show in the browser. How do I accomplish this?

回答1:

If you use return Controller.File(filename, ...), you'll return a FilePathResult, which probably isn't what you want - I'm assuming that 'image' in your sample is an image filename (a case where 'var' isn't helping anyone...)

If you use one of the other File overloads, or use FileContentResult or FileStreamResult directly, you'll get the effect you want.

You don't need to make a custom ActionResult class (though of course, it might be useful for other reasons.)

HOWEVER, having just written all this, I've realised that your problem is that TIFF is not a file format which browsers can always (ever?) display internally, which is probably why they're prompting for a download.

You will need to re-render it to a PNG or something on the server to display in a browser.

回答2:

The File ActionResult adds a line to the HTTP header like this:

Content-disposition: attachment; filename=foo

This will cause the browser to attempt to download the file. That's why there is an overload to specify the filename.

You can create your own ActionResult to do the downloading, and omit the Content-disposition.

If you want to copy-and-paste, I have the code for one on codeplex: ImageResult.cs

回答3:

As requested, here is my solution.

Here is the ImageResult class, copied and modified from John

public class ImageResult : ActionResult
{
    public ImageResult()
    {
    }

    public byte[] ImageData
    {
        get;
        set;
    }

    public MemoryStream ImageStream
    {
        get;
        set;
    }

    public string MimeType
    {
        get;
        set;
    }

    public HttpCacheability Cacheability
    {
        get;
        set;
    }

    public string ETag
    {
        get;
        set;
    }

    public DateTime? Expires
    {
        get;
        set;
    }

    public override void ExecuteResult(ControllerContext context)
    {
        if (this.ImageData == null && ImageStream == null)
        {
            throw new ArgumentNullException("ImageData or ImageStream");
        }

        if (string.IsNullOrEmpty(this.MimeType))
        {
            throw new ArgumentNullException("MimeType");
        }

        context.HttpContext.Response.ContentType = this.MimeType;

        if (!string.IsNullOrEmpty(this.ETag))
        {
            context.HttpContext.Response.Cache.SetETag(this.ETag);
        }

        if (this.Expires.HasValue)
        {
            context.HttpContext.Response.Cache.SetCacheability(this.Cacheability);
            context.HttpContext.Response.Cache.SetExpires(this.Expires.Value);
        }

        if (ImageStream != null)
        {
            ImageData = ImageStream.ToArray();
        } 

        context.HttpContext.Response.OutputStream.Write(this.ImageData, 0, this.ImageData.Length);

    }
}

Here is my action, modified for clarity

public ActionResult Index(ItemImageRequest request)
{
    var result = queueService.GetItemImage(request);

    if (result.TotalResults == 0)
        return new EmptyResult();

    ItemImage image = result.FirstResult;

    //image.Image is type byte[]
    MemoryStream tiffStream = new MemoryStream(image.Image);

    MemoryStream pngStream = new MemoryStream();

    System.Drawing.Bitmap.FromStream(tiffStream).Save(pngStream, System.Drawing.Imaging.ImageFormat.Png);

    return new ImageResult()
    {
        ImageStream = pngStream,
        MimeType = "image/png",
        Cacheability = HttpCacheability.NoCache
    };
}

Thanks to John and Will for helping me out with this.

来源：https://stackoverflow.com/questions/5172380/render-image-to-the-screen-from-mvc-controller