c# - 动态写入图像

我在Web表单的代码背后动态生成了三个值。这三个值将显示给用户。尽管这听起来有些奇怪，但我不希望用户能够复制和粘贴这些值。因此，我想通过动态生成的图像写出值。

我的问题是，有没有一种方法可以动态创建图像并将其写到响应中？我不想创建图像，将其保存到服务器，然后将URL传递回页面。我真的很想在响应中写出二进制内容。这可能吗？如果是这样，有人可以解释/显示如何吗？

最佳答案

在简化列表中，您可以使用context.Response.BinaryWrite()将字节数组写入响应流。通常，您将从映射到特定mime类型（即* .jpg或* .png等）的自定义http处理程序中调用此方法。

以下代码块显示了一种创建简单的capcha图像并将其作为字节数组返回的方式，该字节数组可以由context.Response.BinaryWrite()使用

private Byte[] GenerateImage()
{
  RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
  Byte[] rand = new Byte[200];
  rng.GetBytes(rand);
  int i = 0;

  Bitmap bmp = new Bitmap(_imageWidth, _imageHeight, PixelFormat.Format24bppRgb);
  Bitmap cloneBmp = null;
  Graphics g = null;
  LinearGradientBrush backgroundBrush = null;
  LinearGradientBrush textBrush = null;
  SolidBrush[] circleBrush = new SolidBrush[3];
  Font font = null;
  GraphicsPath path = null;

  try
  {
    g = Graphics.FromImage(bmp);
    g.SmoothingMode = SmoothingMode.AntiAlias;
    Rectangle r = new Rectangle(0, 0, _imageWidth, _imageHeight);
    backgroundBrush = new LinearGradientBrush(
            new RectangleF(0, 0, _imageWidth, _imageHeight),
            Color.FromArgb(rand[i++] / 2 + 128, rand[i++] / 2 + 128, 255),
            Color.FromArgb(255, rand[i++] / 2 + 128, rand[i++] / 2 + 128),
            rand[i++] * 360 / 256);
    g.FillRectangle(backgroundBrush, r);

    for (int br = 0; br < circleBrush.Length; br++)
    {
      circleBrush[br] = new SolidBrush(Color.FromArgb(128, rand[i++], rand[i++], rand[i++]));
    }

    for (int circle = 0; circle < 30; circle++)
    {
      int radius = rand[i++] % 10;
      g.FillEllipse(circleBrush[circle % 2],
          rand[i++] * _imageWidth / 256,
          rand[i++] * _imageHeight / 256,
          radius, radius);
    }

    font = new Font("Tahoma", _imageHeight / 2, FontStyle.Regular);
    StringFormat format = new StringFormat();
    format.Alignment = StringAlignment.Center;
    format.LineAlignment = StringAlignment.Center;

    path = new GraphicsPath();
    path.AddString(_challengeKey, font.FontFamily, (int)font.Style, font.Size, r, format);

    textBrush = new LinearGradientBrush(
            new RectangleF(0, 0, _imageWidth, _imageHeight),
            Color.FromArgb(rand[i] % 128, rand[i] % 128, rand[i++] % 128),
            Color.FromArgb(rand[i] % 128, rand[i] % 128, rand[i++] % 128),
            rand[i++] * 360 / 256);
    g.FillPath(textBrush, path);

    cloneBmp = (Bitmap)bmp.Clone();

    int distortionSeed = rand[i++];
    double distortion = distortionSeed > 128 ? 5 + (distortionSeed - 128) % 5 : -5 - distortionSeed % 5;
    for (int y = 0; y < _imageHeight; y++)
    {
      for (int x = 0; x < _imageWidth; x++)
      {
        // Adds a simple wave
        int newX = (int)(x + (distortion * Math.Sin(Math.PI * y / 96.0)));
        int newY = (int)(y + (distortion * Math.Cos(Math.PI * x / 64.0)));
        if (newX < 0 || newX >= _imageWidth)
        {
          newX = 0;
        }
        if (newY < 0 || newY >= _imageHeight)
        {
          newY = 0;
        }
        bmp.SetPixel(x, y, cloneBmp.GetPixel(newX, newY));
      }
    }

    MemoryStream stream = new MemoryStream();
    bmp.Save(stream, ImageFormat.Jpeg);
    return stream.ToArray();
  }
  finally
  {
    if (backgroundBrush != null)
    {
      backgroundBrush.Dispose();
    }
    if (textBrush != null)
    {
      textBrush.Dispose();
    }
    for (int br = 0; br < circleBrush.Length; br++)
    {
      if (circleBrush[br] != null)
      {
        circleBrush[br].Dispose();
      }
    }
    if (font != null)
    {
      font.Dispose();
    }
    if (path != null)
    {
      path.Dispose();
    }
    if (g != null)
    {
      g.Dispose();
    }
    if (bmp != null)
    {
      bmp.Dispose();
    }
    if (cloneBmp != null)
    {
      cloneBmp.Dispose();
    }
  }
}

这是您的HTTP处理程序的外观。请注意，这是非常基本的操作，可以完成工作，但不包括任何要用于性能提升的客户端或服务器端图像缓存代码。

 public class ImageHandler : IHttpHandler
  {
    public bool IsReusable
    {
      get
      {
        return true;
      }
    }

    public void ProcessRequest(HttpContext context)
    {
        context.Response.ContentType = MimeTypeConstants.JPG;
        context.Response.Clear();
        context.Response.BinaryWrite(GenerateImage());
        context.Response.End();
    }
  }

请享用！

关于c# - 动态写入图像，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/3104278/