Creating an image from the memorystream

[Paul Douglas]

I have to created a function which compresses an image, but rather than save
it to a physical file I want to save it to memory and return the stream as
an image object from the function. How would you do this? can this be done?


' make a memory stream to work with the image bytes
Dim imgStream As New MemoryStream()
'Save the image with a filename that indicates
' the compression quality used
oImg.Save(imgStream, imgICI, encoderParams)
' make byte array the same size as the image
Dim imageContent(imgStream.Length) As Byte
'rewind the memory stream
imgStream.Position = 0
'load the byte array with the image
imgStream.Read(imageContent, 0, CInt(imgStream.Length))
Dim bw As New BinaryWriter(imgStream)
'******* Error Generated ****************
Return CType(bw.BaseStream(), Image)
'*****************************************

Thanks in advance
Paul

[Mattias Sjögren]

Paul,

> ' make byte array the same size as the image
> Dim imageContent(imgStream.Length) As Byte

Keep in mind that the number within the parentheses indicates the
upper bound of the array, not the length, so you're allocating one
more byte than you need here. It should be

Dim imageContent(imgStream.Length - 1) As Byte


> Dim bw As New BinaryWriter(imgStream)
> '******* Error Generated ****************
> Return CType(bw.BaseStream(), Image)
> '*****************************************

That should probably be

Return Image.FromStream(imgStream)

The BinaryWriter object isn't needed AFAICT.

But the new Image object you return will probably uncompress the data
from the stream into its internal format, so I don't see the point in
doing this. You could replace the entire procedure with

Return oImg.Clone()



Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/
Please reply only to the newsgroup.

[Paul Douglas]

Worked a treat. Thanks
Mattias Sjögren <mattias.dont.want.spam@mvps.org> wrote:
>Paul,
>
>> ' make byte array the same size as the image
>> Dim imageContent(imgStream.Length) As Byte
>
>Keep in mind that the number within the parentheses indicates the
>upper bound of the array, not the length, so you're allocating one
>more byte than you need here. It should be
>
>Dim imageContent(imgStream.Length - 1) As Byte
>
>
>> Dim bw As New BinaryWriter(imgStream)
>> '******* Error Generated ****************
>> Return CType(bw.BaseStream(), Image)
>> '*****************************************
>
>That should probably be
>
>Return Image.FromStream(imgStream)
>
>The BinaryWriter object isn't needed AFAICT.
>
>But the new Image object you return will probably uncompress the data
>from the stream into its internal format, so I don't see the point in
>doing this. You could replace the entire procedure with
>
>Return oImg.Clone()
>
>
>
>Mattias
>
>--
>Mattias Sjögren [MVP] mattias @ mvps.org
>http://www.msjogren.net/dotnet/
>Please reply only to the newsgroup.