如何在.net中保存具有4-2-2和高质量的jpeg?

当我使用bitmap.save保存jpg文件时,当我指定编码器和质量时,它会保存为jpeg 4-1-1,而当我不指定编码器和质量时,它会保存为4-2-2。我想将其保存为4-2-2,质量高于默认值。可以使用bitmap.save吗?我用4-1-1储蓄有什么损失吗?

Dim bmp As Bitmap
Dim ep As New EncoderParameters(1)
Dim sysCodecs() As ImageCodecInfo
Dim jpgCodec, cdc As ImageCodecInfo

sysCodecs = ImageCodecInfo.GetImageEncoders()

' get jpg codec
jpgCodec = Nothing
For Each cdc In sysCodecs
  If String.Compare(cdc.MimeType, "image/jpeg", True) = 0 Then
    jpgCodec = cdc
    Exit For
  End If
Next cdc

If jpgCodec IsNot Nothing Then
  ep.Param(0) = New EncoderParameter(Encoder.Quality, 97)
  bmp = Bitmap.FromFile(filename)
  bmp.Save(outname, jpgCodec, ep) ' saves 4-1-1
  bmp.Save(outname) ' saves 4-2-2
end if