Images Lazy Loading

Imports System.ComponentModel
Imports System.IO
Imports System.Windows.Forms

Public Class Form1
    Private ImageFolderPath As String = "Chemin_vers_le_dossier_des_images"
    Private ImageList As New ImageList()
    Private Thumbnails As New List(Of ImageInfo)()
    Private Loading As Boolean = False
    Private WithEvents backgroundWorker As New BackgroundWorker()

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ListView1.View = View.LargeIcon
        ListView1.LargeImageList = ImageList

        ' Gérez le défilement pour charger les images à la demande.
        AddHandler ListView1.Scroll, AddressOf ListView1_Scroll

        ' Configurez le BackgroundWorker.
        backgroundWorker.WorkerReportsProgress = True
        backgroundWorker.WorkerSupportsCancellation = True

        ' Chargez les images initiales (par exemple, les 50 premières images).
        LoadInitialImages(50)
    End Sub

    Private Sub ListView1_Scroll(sender As Object, e As ScrollEventArgs)
        ' Chargez plus d'images lorsque l'utilisateur fait défiler.
        If Not Loading AndAlso e.NewValue + ListView1.ClientSize.Height >= ListView1.Items.Count * ListView1.Items(0).Bounds.Height Then
            LoadMoreImages(50)
        End If
    End Sub

    Private Sub LoadInitialImages(count As Integer)
        For i As Integer = 0 To count - 1
            Dim imagePath As String = Path.Combine(ImageFolderPath, $"image_{i}.jpg")
            If File.Exists(imagePath) Then
                Dim thumbnail As Image = GetThumbnail(imagePath)
                If thumbnail IsNot Nothing Then
                    ImageList.Images.Add(thumbnail)
                    Thumbnails.Add(New ImageInfo() With {.FilePath = imagePath, .Thumbnail = thumbnail})
                End If
            End If
        Next

        ' Ajoutez les images à la ListView.
        For Each imageInfo As ImageInfo In Thumbnails
            Dim item As New ListViewItem()
            item.ImageIndex = ImageList.Images.Count - 1
            ListView1.Items.Add(item)
        Next
    End Sub

    Private Sub LoadMoreImages(count As Integer)
        ' Utilisez le BackgroundWorker pour charger les images en arrière-plan.
        If Not backgroundWorker.IsBusy Then
            Loading = True
            backgroundWorker.RunWorkerAsync(count)
        End If
    End Sub

    Private Sub backgroundWorker_DoWork(sender As Object, e As DoWorkEventArgs) Handles backgroundWorker.DoWork
        Dim count As Integer = CInt(e.Argument)
        Dim startIndex As Integer = Thumbnails.Count

        For i As Integer = startIndex To startIndex + count - 1
            If backgroundWorker.CancellationPending Then
                e.Cancel = True
                Exit For
            End If

            Dim imagePath As String = Path.Combine(ImageFolderPath, $"image_{i}.jpg")
            If File.Exists(imagePath) Then
                Dim thumbnail As Image = GetThumbnail(imagePath)
                If thumbnail IsNot Nothing Then
                    Thumbnails.Add(New ImageInfo() With {.FilePath = imagePath, .Thumbnail = thumbnail})
                    backgroundWorker.ReportProgress(i)
                End If
            End If
        Next
    End Sub

    Private Sub backgroundWorker_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles backgroundWorker.ProgressChanged
        ' Ajoutez les images chargées à la ListView.
        Dim index As Integer = e.ProgressPercentage
        Dim imageInfo As ImageInfo = Thumbnails(index)
        ImageList.Images.Add(imageInfo.Thumbnail)
        Dim item As New ListViewItem()
        item.ImageIndex = ImageList.Images.Count - 1
        ListView1.Items.Add(item)
    End Sub

    Private Sub backgroundWorker_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles backgroundWorker.RunWorkerCompleted
        Loading = False
    End Sub

    Private Sub Form1_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
        ' Annulez le BackgroundWorker s'il est en cours d'exécution.
        If backgroundWorker.IsBusy Then
            backgroundWorker.CancelAsync()
        End If
    End Sub

    Private Function GetThumbnail(imagePath As String) As Image
        ' Code pour créer et retourner une miniature de l'image.
        ' Par exemple, vous pouvez utiliser la classe Bitmap pour redimensionner l'image.
        ' Assurez-vous de gérer les erreurs et de libérer les ressources correctement.
        Try
            Dim originalImage As New Bitmap(imagePath)
            Dim thumbnail As New Bitmap(100, 100) ' Redimensionnez la miniature selon vos besoins.
            Using g As Graphics = Graphics.FromImage(thumbnail)
                g.DrawImage(originalImage, 0, 0, thumbnail.Width, thumbnail.Height)
            End Using
            originalImage.Dispose()
            Return thumbnail
        Catch ex As Exception
            Return Nothing
        End Try
    End Function
End Class

Public Class ImageInfo
    Public Property FilePath As String
    Public Property Thumbnail As Image
End Class