Object reference not set to an instance of an object. System.Drawing.Image Save-CodePudding

Not sure why I am getting this error on the last line of code MyOnlineImg.Save. I am using Visual Studio 2017 on Windows 10 Pro. I am pretty sure the code used to work. When I debug it everything seems normal to me.

Dim MyOnlineImg As System.Drawing.Image
MyOnlineImg = GetImagefromDB(ImgID, Now)
Dim ms As New MemoryStream()
Dim myImageCodecInfo As ImageCodecInfo
Dim myEncoder As System.Drawing.Imaging.Encoder
Dim myEncoderParameter As EncoderParameter
Dim myEncoderParameters As EncoderParameters
myImageCodecInfo = GetEncoderInfo(ImageFormat.Png)
myEncoderParameters = New EncoderParameters(1)
myEncoder = System.Drawing.Imaging.Encoder.Quality
myEncoderParameter = New EncoderParameter(myEncoder, CType(50L, Int32))
myEncoderParameters.Param(0) = myEncoderParameter
MyOnlineImg.Save(ms, myImageCodecInfo, myEncoderParameters)

I also tried this but I still had the same error.

ms = {System.IO.MemoryStream} 
pngCodec = {System.Drawing.Imaging.ImageCodecInfo}
myEncoderParameters = {System.Drawing.Imaging.EncoderParameters}

Code:

    Dim ms As New MemoryStream()
    Dim myImageCodecInfo As ImageCodecInfo
    Dim myEncoder As System.Drawing.Imaging.Encoder
    'Dim myEncoderParameter As EncoderParameter
    'Dim myEncoderParameters As EncoderParameters
    myImageCodecInfo = GetEncoderInfo(ImageFormat.Png) 'lets think about switching from PNG to JPG to speed up performance (reduce quality)
    'myEncoderParameters = New EncoderParameters(1)
    myEncoder = System.Drawing.Imaging.Encoder.Quality
    'myEncoderParameter = New EncoderParameter(myEncoder, CType(50L, Int32))
    'myEncoderParameters.Param(0) = myEncoderParameter


    Dim pngCodec As ImageCodecInfo = GetEncoderInfo(ImageFormat.Png)
    Dim myEncoderParameters As New EncoderParameters()
    myEncoderParameters.Param(0) = New EncoderParameter(Encoder.Quality, 50)

    Dim MyOnlineImg As System.Drawing.Image = GetImagefromDB(ImgID, Now)
    'Dim ms As New MemoryStream()
    MyOnlineImg.Save(ms, pngCodec, myEncoderParameters)

I tried adding tests for nulls with breakpoints but they were all ok:

If ms Is Nothing Then
        Dim blah As String = ""
    End If
    If pngCodec Is Nothing Then
        Dim blah As String = ""
    End If
    If myEncoderParameters Is Nothing Then
        Dim blah As String = ""
    End If

CodePudding user response：

Try this (after adding appropriate Imports directives at the top of the file):

Dim pngCodec As ImageCodecInfo = GetEncoderInfo(ImageFormat.Png)
Dim myEncoderParameters As New EncoderParameters()
myEncoderParameters.Param(0) = New EncoderParameter(Encoder.Quality, 50)

Dim MyOnlineImg As Image = GetImagefromDB(ImgID, Now)
Dim ms As New MemoryStream()
MyOnlineImg.Save(ms, pngCodec, myEncoderParameters)

If it doesn't work, check that GetEncoderInfo() and GetImagefromDB() do what you expect, and that neither return Nothing.

CodePudding user response：

I found that Image was corrupted. Thanks!