在具有静态标签的面板内滚动图片框

Question

我在 Panel 中有一个 PictureBox，用于在图片很大时获得自动滚动条，一个带有照片标题的 Label。
如果我将 Label 放在 PictureBox 上，“透明”背景颜色会正确显示，但 Label 仍位于 PictureBox 的顶部，并且如果我向上或向下滚动面板的滚动条，它就会离开屏幕！

相反，如果我将标签放在面板之外（在表单上方），标签会如我所愿在屏幕顶部保持静态，但透明背景色无法正确显示，会变为不透明。

然后，如果我将Label的Parent属性设置为PictureBox，透明背景色又可以正常工作了，但是Label的静态位置不再被尊重并再次加入PictureBox！

使用 Panel 的滚动条时，如何在 PictureBox 上获得具有透明背景色的静态标签？

Answer 1

我已经测试了覆盖表单。它似乎在您的上下文中运行良好。
PasteBin中的源代码
将修改后的项目上传到OneDrive
（我没有 FW 4.5.2，用 FW 4.5.1 和 FW 4.7.1 测试过）

Overlay 可能是一个有趣的功能，但是，正如我已经说过的，这也可以使用 TextRender.DrawText() 或 Graphics.DrawString() 来完成，并由滚动图片容器时偏移绘制的文本所需的简单数学支持。

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在您的项目中，我删除了 Label1 以及所有对它的引用。
然后，我设置了这个类字段：

Private OverlayShown As Boolean = False

在frmPho_Load()

Overlay.Size = New Size(200, 50)
Overlay.OverlayPosition = Overlay.Alignment.Center
Overlay.Reposition(Me.Location, Me.Size)
OverlayShown = True
Overlay.Visible = False
Overlay.Show(Me)

在frmPho_Deactivate():

If OverlayShown = False Then
    antip.Width = Me.Width
    antip.Height = Me.Height
    antip.Visible = True
End If
OverlayShown = False

这些是对使用 Overlay 的托管表单 (Form4) 所做的所有更改。

Public Class frmPho

    Private Overlay As New OverlayForm

    Private Sub frmPho_Load(sender As Object, e As EventArgs) Handles Me.Load
        Overlay.Size = New Size(200, 50)
        Overlay.OverlayPosition = Overlay.Alignment.Center
        Overlay.Reposition(Me.Location, Me.Size)
        OverlayShown = True
        Overlay.Visible = False
        Overlay.Show(Me)
        '(...)
        Overlay.Text = IO.Path.GetFileNameWithoutExtension(_ImageFileNames(_CurrentImage))
    End Sub

    Private Sub CheckBox1_CheckedChanged(sender As Object, e As EventArgs) Handles CheckBox1.CheckedChanged
        If CheckBox1.CheckState = False Then
            Overlay.Visible = False
        Else
            OverlayShown = True
            Overlay.Visible = True
        End If
    End Sub

    Private Sub ShowPrevImage()
        '(...)
        OverlayShown = True
        Overlay.Text = IO.Path.GetFileNameWithoutExtension(_ImageFileNames(_CurrentImage))
    End Sub

    Private Sub ShowNextImage()
        '(...)
        OverlayShown = True
        Overlay.Text = IO.Path.GetFileNameWithoutExtension(_ImageFileNames(_CurrentImage))
    End Sub

    Private Sub frmPho_Deactivate(sender As Object, e As EventArgs) Handles Me.Deactivate
        If OverlayShown = False Then
            antip.Width = Me.Width
            antip.Height = Me.Height
            antip.Visible = True
        End If
        OverlayShown = False
    End Sub

    Private Sub frmPho_Move(sender As Object, e As EventArgs) Handles Me.Move
        Overlay.Reposition(Me.Location, Me.Size)
    End Sub

    Private Sub frmPho_Resize(sender As Object, e As EventArgs) Handles Me.Resize
        Overlay.Reposition(Me.Location, Me.Size)
    End Sub

    Private Sub frmPho_Shown(sender As Object, e As EventArgs) Handles Me.Shown
        ShowOverlay(300)
    End Sub

    Private Async Sub ShowOverlay(Delay As Integer)
        Await Task.Delay(Delay)
        Overlay.Visible = True
        Me.Focus()
    End Sub

这是完整的 OverlayForm：

所有边框/控制框都为无（这是一个无边框的表单）
.StartPosition = 手动
.TransparncyKey = WhiteSmoke 取决于字体颜色（需要时修改）
.BackColor = WhiteSmoke 取决于字体颜色（需要时修改）
.ShowInTaskbar = False

Public Class OverlayForm

    Private _Text As String
    Private TextPosition As Point
    Private _Brush As SolidBrush = New SolidBrush(Color.White)
    Private _Flags As StringFormatFlags = StringFormatFlags.NoWrap

    Public Enum Alignment
        Left = 0
        Right = 1
        Center = 2
    End Enum

    Public Sub New()
        InitializeComponent()
    End Sub

    Public Overrides Property Text() As String
        Get
            Return Me._Text
        End Get
        Set(ByVal value As String)
            _Text = value
            Me.Invalidate()
        End Set
    End Property

    Public Property OverlayPosition As Alignment

    Private Sub OverlayForm_Paint(sender As Object, e As PaintEventArgs) Handles Me.Paint

        e.Graphics.TextRenderingHint = Drawing.Text.TextRenderingHint.SingleBitPerPixelGridFit
        e.Graphics.TextContrast = 12
        Dim _Size As SizeF = e.Graphics.MeasureString(Me._Text, Me.Font,
                                                      New SizeF(Me.Width, Me.Height),
                                                      New StringFormat(Me._Flags))

        e.Graphics.DrawString(Me._Text, Me.Font, Me._Brush, New RectangleF(TextAlign(_Size.Width), _Size))

    End Sub

    Private Sub OverlayForm_ForeColorChanged(sender As Object, e As EventArgs) Handles Me.ForeColorChanged
        Me._Brush = New SolidBrush(Me.ForeColor)
        Me.Invalidate()
    End Sub

    Public Sub Reposition(ParentPosition As Point, ParentSize As Size)
        Select OverlayPosition
            Case Alignment.Left
                Me.Location = New Point(ParentPosition.X + 20, ParentPosition.Y + 40)
            Case Alignment.Right
                Me.Location = New Point(ParentSize.Width - Me.Width - 20, ParentPosition.Y + 40)
            Case Alignment.Center
                 Me.Location = New Point(ParentPosition.X + 20 + (ParentSize.Width \ 2) - (Me.Width \ 2), ParentPosition.Y + 40)
        End Select
    End Sub

    Private Function TextAlign(TextWidth As Single) As PointF
        Select Case OverlayPosition
            Case Alignment.Left
                Return New PointF(1, 1)
            Case Alignment.Right
                Return New PointF((Me.Width - TextWidth) - 1, 1)
            Case Alignment.Center
                If TextWidth > Me.Width Then TextWidth = Me.Width - 2
                Return New PointF(CSng((Me.Width - TextWidth) / 4) - 1, 1)
        End Select
    End Function

End Class