c# – 确保导出的JPEG小于最大文件大小

我正在使用C#作为演示者应用程序,它通过下面的过程将屏幕截图编码成JPEG.我担心的是,使用静态压缩设置时,图像质量会有很大变化.如果我有应用程序捕获我的屏幕,当我有Visual Studio全屏幕时,图像输出将是?200 KB,但如果我最小化我的屏幕并显示我的桌面背景,那将是?400 KB.

我可以将编码过程放在一个循环中,并持续减小图像大小,直到字节数组的大小小于300 KB,但这似乎是一个繁琐的操作.有没有其他方法可以使用？

提前致谢.

// get the screenshot
System.Drawing.Rectangle totalSize = System.Drawing.Rectangle.Empty;
//foreach (Screen s in Screen.AllScreens)
totalSize = System.Drawing.Rectangle.Union(totalSize,Screen.PrimaryScreen.Bounds);
Bitmap screenShotBitmap = new Bitmap(totalSize.Width,totalSize.Height,System.Drawing.Imaging.PixelFormat.Format32bppRgb);
screenShotBitmap.SetResolution(96,96);
Graphics screenShotGraphics = Graphics.FromImage(screenShotBitmap);
screenShotGraphics.CopyFromScreen(totalSize.X,totalSize.Y,totalSize.Size,CopyPixelOperation.SourceCopy);
screenShotGraphics.Dispose();

// image codec information
ImageCodecInfo imageCodecInfo = GetEncoderInfo("image/jpeg");

// encoder settings
System.Drawing.Imaging.Encoder encoderQuality;
System.Drawing.Imaging.Encoder encoderColor;
encoderQuality = System.Drawing.Imaging.Encoder.Quality;
encoderColor = System.Drawing.Imaging.Encoder.ColorDepth;

// compression & quality for JPEG output
Int64 quality = 40L;

// storage for exported JPEG
byte[] screenShotByteArray;

// encoder parameters
EncoderParameter encoderQualityParameter = new EncoderParameter(encoderQuality,quality);
//EncoderParameter encoderColorParameter = new EncoderParameter(encoderColor,8L);

// encoder parameters table
EncoderParameters encoderParameters = new EncoderParameters(1);
encoderParameters.Param[0] = encoderQualityParameter;
//encoderParameters.Param[1] = encoderColorParameter;

// get the code into a memory stream
MemoryStream screenShotMemoryStream = new MemoryStream();
screenShotBitmap.Save(screenShotMemoryStream,imageCodecInfo,encoderParameters);

// convert to a byte array
screenShotByteArray = screenShotMemoryStream.GetBuffer();

// close the memory stream
screenShotMemoryStream.Close();