.net - 相同的代码在不同的服务器上产生不一致的图像质量

Question

拍摄以下两张图片:

开发版 - IIS7 Windows 7 Pro 64 位机器



实时版本 - IIS7 Windows Server 2008 64 位机器



请注意 Live 版本是如何“像素化”的并且看起来质量很低，而 Dev 版本是平滑的、抗锯齿的并且看起来不错。这些都是由相同的代码生成的:

' Settings
Dim MaxHeight As Integer = 140
Dim MaxWidth As Integer = 140
Dim WorkingFolderPath As String = "\\server\share\bla\"
Dim AllowedFileExtensions As New ArrayList
AllowedFileExtensions.Add(".jpg")
AllowedFileExtensions.Add(".jpeg")

' Select an image to use from the WorkingFolder
Dim ImageFileName As String = ""
Dim WorkingFolder As New IO.DirectoryInfo(WorkingFolderPath)
Dim SourceImages As IO.FileInfo() = WorkingFolder.GetFiles()

For Each SourceImage As IO.FileInfo In SourceImages
    If AllowedFileExtensions.Contains(SourceImage.Extension.ToLower) = True Then
        ImageFileName = SourceImage.Name
    End If
Next

' Determine path to selected image (if no image was found use a placeholder)
Dim PhysicalPath As String = ""
If ImageFileName = "" Then
    ' No Image was found, use the filler image
    PhysicalPath = Server.MapPath("ProductOfTheMonthMissing.jpg")
Else
    ' An Image was found, Redirect to it / build path for Thumnailing
    If Request.QueryString("FullSize") = "true" Then
        Response.Redirect("../share/bla/" & ImageFileName)
    Else
        PhysicalPath = WorkingFolderPath & ImageFileName
    End If
End If

' Load image and output in binary (resizing if necessary)
Using ProductImage As System.Drawing.Image = System.Drawing.Image.FromFile(PhysicalPath)
    Dim newWidth As Integer = ProductImage.Width
    Dim newHeight As Integer = ProductImage.Height

    ' Check if selected size is too big, if so, determine new size
    If ProductImage.Width > MaxWidth Or ProductImage.Height > MaxHeight Then
        Dim ratioX As Double = CDbl(MaxWidth) / ProductImage.Width
        Dim ratioY As Double = CDbl(MaxHeight) / ProductImage.Height
        Dim ratio As Double = Math.Min(ratioX, ratioY)

        newWidth = CInt(ProductImage.Width * ratio)
        newHeight = CInt(ProductImage.Height * ratio)
    End If

    ' Create a new bitmap from the image with new size
    Dim Codecs As ImageCodecInfo() = ImageCodecInfo.GetImageEncoders()
    Dim CodecInfo As ImageCodecInfo = Nothing
    Dim ProductOfTheMonth As New Bitmap(ProductImage, newWidth, newHeight)
    Dim ReSizer As Graphics = Graphics.FromImage(ProductOfTheMonth)

    ReSizer.InterpolationMode = InterpolationMode.HighQualityBicubic
    ReSizer.SmoothingMode = SmoothingMode.HighQuality
    ReSizer.PixelOffsetMode = PixelOffsetMode.HighQuality
    ReSizer.CompositingQuality = CompositingQuality.HighQuality

    ' Ensure the encoder uses the best quality settings
    Dim EncoderParams As New EncoderParameters(3)
    EncoderParams.Param(0) = New EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L)
    EncoderParams.Param(1) = New EncoderParameter(System.Drawing.Imaging.Encoder.ScanMethod, CInt(EncoderValue.ScanMethodInterlaced))
    EncoderParams.Param(2) = New EncoderParameter(System.Drawing.Imaging.Encoder.RenderMethod, CInt(EncoderValue.RenderProgressive))

    ' Set jpeg as the output codec
    For Each Codec As ImageCodecInfo In Codecs
        If Codec.MimeType = "image/jpeg" Then
            CodecInfo = Codec
        End If
    Next

    ' Ready a memory stream and byte array
    Dim MemStream As New MemoryStream()
    Dim bmpBytes As Byte()

    ' Save the image the the memory stream & prep ContentType for HTTP reasponse
    Response.ContentType = "image/jpeg"
    ProductOfTheMonth.Save(MemStream, CodecInfo, EncoderParams)

    ' Flush memory stream into byte array & flush to browser
    bmpBytes = MemStream.GetBuffer()
    Response.BinaryWrite(bmpBytes)

    ' Cleanup
    ProductOfTheMonth.Dispose()
    MemStream.Close()
    ProductImage.Dispose()
End Using

这背后的原因是什么以及我如何解决这个问题？大概是实时网络服务器上的 GD 问题 - 但我不知道是什么 - 我试图尽可能彻底地设置图形和编解码器设置，但它仍然不同？

编辑:两个示例中的源图像也是相同的(位于中央 unc 共享上)-源图像的副本 here

Answer 1

我已经和，在这里回答了一个类似的问题:Graphics wrong image interpolation in .Net ，但简而言之，似乎不同的平台使用不同的内部算法(或者它可能是 GDI 中的内部舍入问题)。

无论如何，问题出在设置上。因此，请尝试以下操作:

Using s As Bitmap = DirectCast(Bitmap.FromFile(PhysicalPath), Bitmap)
    Dim scale As Double = Math.Min(140.0 / s.Width, 140.0 / s.Height)
    Using d As New Bitmap(CInt(Math.Floor(scale * s.Width)), CInt(Math.Floor(scale * s.Height)), System.Drawing.Imaging.PixelFormat.Format24bppRgb)
        Using dg As Graphics = Graphics.FromImage(d)
            dg.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic
            dg.SmoothingMode = SmoothingMode.HighQuality
            dg.PixelOffsetMode = PixelOffsetMode.HighQuality
            dg.CompositingQuality = CompositingQuality.HighQuality
            dg.Clear(Color.White)
            dg.DrawImage(s, New Rectangle(0, 0, d.Width, d.Height), New Rectangle(0, 0, s.Width, s.Height), GraphicsUnit.Pixel)
        End Using

        Dim jpegArgs As New EncoderParameters(3)
        jpegArgs.Param(0) = New EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 100L)
        jpegArgs.Param(1) = New EncoderParameter(System.Drawing.Imaging.Encoder.ScanMethod, CInt(EncoderValue.ScanMethodInterlaced))
        jpegArgs.Param(2) = New EncoderParameter(System.Drawing.Imaging.Encoder.RenderMethod, CInt(EncoderValue.RenderProgressive))

        Dim Codecs As ImageCodecInfo() = ImageCodecInfo.GetImageEncoders()
        Dim jpegParams As ImageCodecInfo = Nothing

        '#### Set jpeg as the output codec
        For Each Codec As ImageCodecInfo In Codecs
            If Codec.MimeType = "image/jpeg" Then
                jpegParams = Codec
            End If
        Next

        Response.Clear()
        Response.ContentType = "image/jpeg"

        d.Save(Response.OutputStream, jpegParams, jpegArgs)
    End Using
End Using

祝你好运!