[RESOLVED] Image File locked

[Mr.No]

Hi

I am curious to find out why an image file is locked when I load it in a picturebox or Image variable using the code below:

picImage.Image = Image.FromFile("abc.tif")

I can work around the locking bit by reading the image file in a memory stream and then load the Image from the memory stream but I was wondering if there was an alternative way to just assign the filename to the picturebox and not having the image file locked.

Thanks

[MrPolite]

no
I've had trouble with this before. Someone tell me if its still the same in .NET 2.0


if you read on MSDN, it says that when you load the image, you are responsible to leave the image filestream open until the image is dispose. That means that the file remains locked until you're done using the image. It's a quite annoying thing I'd say. I think when I wanted to get around this I would clone the image, I cant remember quite clearly.
your code is ok, its .NET

[grilkip]

It would not be much code to just open a stream yourself and say: Image.FromStream and then close the stream

Turns out I'm wrong, the stream must remain open

[MrPolite]

thats exactly what I just said above
arent you just ashamed of yourself
it works fine if you do what he said and duplicate the image. The problem is, it's redundant. If you're dealing with a lot of images, then you're talking about a big loss of performance/memory etc etc
anyone can check this in .net 2.0?

[grilkip]

I only just took you of my ignore list MrPolite

I wonder when you do what Mr No said and load it into memory first and use that stream, would the new Image Object 'encapsulate' the data or would it copy all of the imagedata to a new location?

[MrPolite]

well it has to make a copy somewhere
I'm not sure what he's doing exactly. The memory stream would need to copy the image data to memory, so I think no matter what you do, you'd end up with two copies of the image

[grilkip]

well it has to make a copy somewhere
I'm not sure what he's doing exactly. The memory stream would need to copy the image data to memory, so I think no matter what you do, you'd end up with two copies of the image

If you create an MemoryStream from an image, you are making the copy (from the disk). I was wondering if when you create an image from a MemoryStream is the data from that stream being copied again or is it 'used' directly.

I don't know if I'm making sence, I can hardly follow my own thoughts.

[MrPolite]

makes sense
I believe it'd be used directly. However.... .it seems like you can't load a file into a memory stream directly (or am I wrong?) so I think you'd have to first load the file, then make a copy of it in the memory stream

[Mr.No]

Thanks for the responses guys. Here's the code I currently use, I had a clue from this link Stream

Try
      ofs = New FileStream(sLogoFile, FileMode.Open, FileAccess.Read)
      oMemStream = New MemoryStream(Convert.ToInt32(ofs.Length))
      oBinReader = New BinaryReader(ofs)
      Dim bytesRead As Byte() = oBinReader.ReadBytes(Convert.ToInt32(ofs.Length))
      oMemStream.Write(bytesRead, 0, Convert.ToInt32(ofs.Length))
      ' picLogo.Image.FromStream(oMemStream) ' This doesn't show the image. Why ????
      picLogo.Image = New Bitmap(oMemStream)
 
      ofs.Close()
 
    Catch ex As Exception
    Finally
      ofs = Nothing  ' release file
    End Try

As you can see, its quite a long step just to show an image, I wonder why the PictureBox doesn't have a method for this. Mind you, while I'm typing this it suddenly occurred to me that I could SubClass the PictureBox to expose a method that would be called say ShowImageWithoutLocking. What do you think? Any alternatives?

Thanks

[grilkip]

I'm not sure that this is more efficient because you are still buffering the whole image in a byte-array, you might as well clone it I think. And you don't really need a BinaryReader to do that

Dim bytesRead As Byte(Convert.ToInt32(ofs.Length))
      ofs.Read(bytesRead, 0, Convert.ToInt32(ofs.Length))
      oMemStream.Write(bytesRead, 0, Convert.ToInt32(ofs.Length))
      ' picLogo.Image.FromStream(oMemStream) ' This doesn't show the image. Why ???? 
      'because it is a shared function that [b]returns[/b] an image.
      picLogo.Image = Image.FromStream(oMemStream)

I typed it freehand, so forgive me small errors.

[wossname]

How about...

picturebox1.image = new Bitmap(Image.FromFile(path))

That doesn't lock the file.

[wossname]

Rep me now or later its up to you

[Mr.No]

Wonderful it works.

Thanks

[MrPolite]

How about...

picturebox1.image = new Bitmap(Image.FromFile(path))

That doesn't lock the file.

you dork
that's what I said I've been doing (cloning the image). It's not any more efficient, as you'd be creating a copy of the image anyways
I don't think there is a way to avoid creating a duplicate

[wossname]

It's not cloning the image you retard. Cloning would lock the file. This is just a straight blit from one bound image to an unbound one.

Maybe it not any faster but it takes up hardly any code and its easy to understand.