将位图保存到流中

本文关键字：保存 位图 | 更新日期: 2023-09-27 18:33:44

我正在尝试通过将上传的流保存到位图中，处理此位图并将处理后的位图保存到应保存到FTP文件夹的新流来调整上传 ASP.NET 图像的大小。上传的流已成功保存为位图并正确处理;只是新处理的流有问题，它呈现为损坏的图像。下面是一段代码：

        s = FileUpload1.FileContent;
        Bitmap bitmap = (Bitmap)Bitmap.FromStream(s);
        Bitmap newBmp = new Bitmap(250, 250, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
        newBmp.SetResolution(72F, 72F);
        Graphics newGraphic = Graphics.FromImage(newBmp);
        newGraphic.Clear(Color.White);
        newGraphic.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
        newGraphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
        newGraphic.DrawImage(bitmap, 0, 0, 250, 250);
        newBmp.Save(MapPath("temp.jpg"));
        Stream memoryStream = new MemoryStream();
        newBmp.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Jpeg);

将位图保存到流中

这里的关键是你得到一个空的图像，这几乎总是从一开始就没有被读取的流。

在

将位图写入流后，需要查找回流的开头。 

memoryStream.Seek(0, SeekOrigin.Begin); //go back to start

否则，当您稍后尝试保存该流时，它会从末尾读取流。当位图写入流时，它会追加字节并推进位置。 这是 MVC 中工作的示例代码。

Index.cshtml

@{
    ViewBag.Title = "Index";
}
@using (Html.BeginForm("UploadImage", "BitmapConvert", FormMethod.Post, new { enctype = "multipart/form-data" })){
    <input type="file" name="uploadFile"/>
    <input type="submit" value="Upload"/>
}

位图转换控制器.cs

using System.Drawing;
using System.IO;
using System.Web;
using System.Web.Mvc;
namespace MvcSandbox.Controllers
{
    public class BitmapConvertController : Controller
    {
        public ActionResult Index()
        {
            return View();
        }
        [HttpPost]
        public ActionResult UploadImage(HttpPostedFileBase uploadFile)
        {
            var s = uploadFile.InputStream;
            var bitmap = new Bitmap(s);
            var resizedBitmap = new Bitmap(250, 250, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
            resizedBitmap.SetResolution(72F, 72F);
            using (var g = Graphics.FromImage(resizedBitmap))
            {
                g.Clear(Color.White);
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                g.DrawImage(bitmap, 0, 0, 250, 250);
                resizedBitmap.Save("C:''Test''test.jpg", System.Drawing.Imaging.ImageFormat.Jpeg);
                using (var memoryStream = new MemoryStream())
                {
                    resizedBitmap.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Jpeg);
                    using (var dest = new FileStream("C:''Test''stream.jpg", FileMode.OpenOrCreate))
                    {
                        memoryStream.Seek(0, SeekOrigin.Begin); //go back to start
                        memoryStream.CopyTo(dest);
                    }
                }
            }
            return RedirectToAction("Index");
        }
    }
}
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