How to save ImageList

[cevem]

Hi.

I'm building a very small and minimalist Movie Collector application. In the Movie Adding dialog, you can select movie's poster. Movie poster is adding to the ImageList.

Adding Movies



Movies are listing in the main window as ListView thumbs (large view). First time is no problem;

No Problem after the adding



...but restarting program, no thumbs in the items.

Restart Application



Andy idea? Please help me, thanks everybody.

[ForumAccount]

How are you saving the data? What is your database?

[cevem]

How are you saving the data? What is your database?

BinaryFormatter

 Dim FS As New System.IO.FileStream(My.Computer.FileSystem.SpecialDirectories.MyDocuments & "\WatchersList\CommonList.mem", IO.FileMode.Create)
            BinFormatter.Serialize(FS, New ArrayList(MovieList.Items))
            FS.Close()

[ForumAccount]

I guess at this point it depends on what you want stored. You could store just the file location of the poster and then at runtime you would load in all the pictures from their file paths. Another option is to save a Byte array that represents the image and then at runtime you recreate the image. There are so many different ways you could go with this, you could even use a SQLite database to save everything. It depends on the scope of your application.

[bergerkiller]

You could also make an "Album" class, with all members required such as the cover image, title and associated file(s). Next you can store everything in raw data using the BinaryWriter and/or FileStream.

Example of an "Image pointer" class, which will hold the information of an image stored in a certain region in a file. (Stored in PNG format)

Public Class ImagePointer
    Sub New(ByVal Path As String, ByVal SourceFile As String, ByVal ImageOffset As Long, ByVal ImageLength As Long)
        Me.Path = Path
        Me.SourceFile = SourceFile
        Me.ImageOffset = ImageOffset
        Me.ImageLength = ImageLength
    End Sub
    Public Path As String = ""
    Public SourceFile As String = ""
    Public ImageOffset As Long = 0
    Public ImageLength As Long = 0
    Public Function GetImage() As Image
        Dim s As New System.IO.FileStream(Me.SourceFile, IO.FileMode.Open)
        Dim imgbytes(Me.ImageLength) As Byte
        s.Position = Me.ImageOffset
        s.Read(imgbytes, 0, Me.ImageLength)
        s.Close()
        Dim ms As New System.IO.MemoryStream(imgbytes, 0, imgbytes.Length)
        ms.Write(imgbytes, 0, imgbytes.Length)
        GetImage = Image.FromStream(ms)
        ms.Close()
    End Function
End Class

It seems that you could use the Image.FromStream directly on the filestream, but it could also be that I didn't do that since an image length is used.

Storing it is somewhat the same:

            Me._Image = value
            Dim ms As New System.IO.MemoryStream()
            value.Save(ms, System.Drawing.Imaging.ImageFormat.Png)
            Me.imageBytes = ms.ToArray
            ms.Close()

Best is to start with the format to use, like a header. Example:

[totalimagecount] (integer)
for each image
* [imagenamelength] (integer)
* [imagename] (char array)
* [imageoffset] (long)
* [imagesize] (long)
for each image
* [rawdata] (PNG image)

This way you can neglect loading the images you don't want to load.

Note: instead of giving the offset and size of each image, you could also send the header length plus the individual sizes of each image. Could save you a few hundred bytes.

[cevem]

I guess at this point it depends on what you want stored. You could store just the file location of the poster and then at runtime you would load in all the pictures from their file paths. Another option is to save a Byte array that represents the image and then at runtime you recreate the image. There are so many different ways you could go with this, you could even use a SQLite database to save everything. It depends on the scope of your application.

Thanks to the your reply. Please show a sample for SQL, or link? Thanks again.

[cevem]

You could also make an "Album" class, with all members required such as the cover image, title and associated file(s). Next you can store everything in raw data using the BinaryWriter and/or FileStream.

Example of an "Image pointer" class, which will hold the information of an image stored in a certain region in a file. (Stored in PNG format)

Public Class ImagePointer
    Sub New(ByVal Path As String, ByVal SourceFile As String, ByVal ImageOffset As Long, ByVal ImageLength As Long)
        Me.Path = Path
        Me.SourceFile = SourceFile
        Me.ImageOffset = ImageOffset
        Me.ImageLength = ImageLength
    End Sub
    Public Path As String = ""
    Public SourceFile As String = ""
    Public ImageOffset As Long = 0
    Public ImageLength As Long = 0
    Public Function GetImage() As Image
        Dim s As New System.IO.FileStream(Me.SourceFile, IO.FileMode.Open)
        Dim imgbytes(Me.ImageLength) As Byte
        s.Position = Me.ImageOffset
        s.Read(imgbytes, 0, Me.ImageLength)
        s.Close()
        Dim ms As New System.IO.MemoryStream(imgbytes, 0, imgbytes.Length)
        ms.Write(imgbytes, 0, imgbytes.Length)
        GetImage = Image.FromStream(ms)
        ms.Close()
    End Function
End Class

It seems that you could use the Image.FromStream directly on the filestream, but it could also be that I didn't do that since an image length is used.

Storing it is somewhat the same:

            Me._Image = value
            Dim ms As New System.IO.MemoryStream()
            value.Save(ms, System.Drawing.Imaging.ImageFormat.Png)
            Me.imageBytes = ms.ToArray
            ms.Close()

Best is to start with the format to use, like a header. Example:

Thanks for the reply. This is a good code. How to apply this code on ListView?

[bergerkiller]

Well first of all you need public members in the background, which store the information you need:

Public albums As New List(Of Album)
Public Class Album
    Public title As String
    Public files() As String
    Public cover As Image
End Class

When populating your listview, you need to use the imagelist. So before you populate the listview, you populate the imagelist with the images you want to display.

ImageList1.Images.Clear()
ListView1.Items.Clear()
For i As Integer = 0 To currentalbums.Count - 1
    ImageList1.Images.Add(currentalbums(i).cover)
    Dim item As New ListViewItem(currentalbums(i).title)
    item.Tag = currentalbums(i).files
    item.ImageIndex = i
    ListView1.Items.Add(item)
Next

The way you do this is up to you, obviously. You can add functions to load/save information from a stream in your Album class:

Public Sub LoadFrom(ByVal s As IO.Stream, ByVal coversize As Long)
    Dim b As New IO.BinaryReader(s)
    Me.title = b.ReadString()
    ReDim Me.files(b.ReadInt32() - 1)
    For i As Integer = 0 To Me.files.Count - 1
        Me.files(i) = b.ReadString()
    Next
    b.Close()
    Dim imgbytes(coversize - 1) As Byte
    s.Read(imgbytes, 0, coversize)
    s.Close()
    Dim ms As New System.IO.MemoryStream(imgbytes, 0, imgbytes.Length)
    ms.Write(imgbytes, 0, imgbytes.Length)
    Me.cover = Image.FromStream(ms)
    ms.Close()
End Sub

Wrote this from scratch, so it could contain some bugs. Idea is to link everything together, and store certain information globally.
Try to Dispose as much as possible, storing lots of Image objects is never a good idea.

EDIT

I recommend adding a loader class, a class which loads Album information from a source file based on an identifier, like a name. It would make everything a bit easier.

Public Function AlbumLoader.GetAlbum("Album name") As Album