动态地将位图返回到浏览器

Question

我正在裁剪图像,并希望使用ashx处理程序返回它.裁剪代码如下:

public static System.Drawing.Image Crop(string img, int width, int height, int x, int y)
    {
        try
        {
            System.Drawing.Image image = System.Drawing.Image.FromFile(img);
            Bitmap bmp = new Bitmap(width, height, PixelFormat.Format24bppRgb);
            bmp.SetResolution(image.HorizontalResolution, image.VerticalResolution);

            Graphics gfx = Graphics.FromImage(bmp);
            gfx.SmoothingMode = SmoothingMode.AntiAlias;
            gfx.InterpolationMode = InterpolationMode.HighQualityBicubic;
            gfx.PixelOffsetMode = PixelOffsetMode.HighQuality;
            gfx.DrawImage(image, new Rectangle(0, 0, width, height), x, y, width, height, GraphicsUnit.Pixel);
            // Dispose to free up resources
            image.Dispose();
            bmp.Dispose();
            gfx.Dispose();

            return bmp;
        }
        catch (Exception ex)
        {
            return null;
        }
    }

正在返回位图,现在需要通过上下文流将其发送回浏览器,因为我不想创建物理文件.

Answer 1

您真的只需要使用适当的MIME类型通过响应发送它:

using System.Drawing;
using System.Drawing.Imaging;

public class MyHandler : IHttpHandler {

  public void ProcessRequest(HttpContext context) {

    Image img = Crop(...); // this is your crop function

    // set MIME type
    context.Response.ContentType = "image/jpeg";

    // write to response stream
    img.Save(context.Response.OutputStream, ImageFormat.Jpeg);

  }
}

您可以将格式更改为许多不同的内容; 只需检查枚举.