只更新部分图形

Question

请问有没有简单的方法可以只更新部分图文？在下面的示例中，我绘制了 1560 个 10x10px 的小方块，并将其中的 3 个涂成蓝色。这需要相当长的时间（大约 1 秒），可以看到它们是如何在屏幕上绘制的。在下一步中，我想将 3 个蓝色方块移动到不同的位置，这意味着我想保留所有绘制的图形，但是 只将 3 个方块涂回灰色并将另外 3 个方块涂成蓝色。如果我完全重新绘制图片，大约需要 "lot" 的时间。 1 秒。上文提到的。我希望每秒至少达到几帧，因为我正在做一个小型 "animated" 模拟。这意味着，代码不必很性感，但足够简单以用于生命周期很短的程序。

Button4_click 代码中描述的方法很快，但只是因为 只绘制 新方块，清除旧图形。

请注意，我在 Panel1 上绘制，而不是 PictureBox1，这是出于性能方面的建议（避免一些不必要的事件处理程序和刷新）。

草图测试代码：

Private drawPattern As Boolean = False
Private drawBlueRects As Boolean = False
Dim blueBrush As New SolidBrush(Color.Blue)
Dim grayBrush As New SolidBrush(Color.Gray)

Private Sub Panel1_Paint(sender As Object, e As PaintEventArgs) Handles Panel1.Paint
    Dim g As Graphics = e.Graphics
    If drawPattern Then
        Dim StartY As Integer = 250 - 60 ' just set Y for upper set of squares
        For ir = 1 To 6                  ' paint upper set of squares
            For ic = 0 To 120
                g.DrawRectangle(New Pen(Color.Gray), 5 + ic * 10, StartY + ir * 10, 8, 8)
            Next
        Next ir
        StartY = 250 + 10  ' just set Y for bottom set of squares
        For ir = 1 To 6    ' paint bottom set of squares
            For ic = 0 To 120
                g.DrawRectangle(New Pen(Color.Gray), 5 + ic * 10, StartY + ir * 10, 8, 8)
            Next
        Next ir
        For ic = 0 To 120  ' paint middle set of squares
            g.FillRectangle(grayBrush, 5 + ic * 10, 250 + 10, 8, 8)
        Next
        ' paint 3 blue squares
        g.FillRectangle(blueBrush, 155, 250 + 10, 8, 8)
        g.FillRectangle(blueBrush, 165, 250 + 10, 8, 8)
        g.FillRectangle(blueBrush, 175, 250 + 10, 8, 8)
    ElseIf drawBlueRects = True Then
        ' paint 3 blue squares
        g.FillRectangle(blueBrush, 255, 250 + 10, 8, 8)
        g.FillRectangle(blueBrush, 265, 250 + 10, 8, 8)
        g.FillRectangle(blueBrush, 275, 250 + 10, 8, 8)
    End If
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    drawPattern = True
    Panel1.Refresh()
    'Panel1.Refresh()
End Sub

Private Sub Button4_Click(sender As Object, e As EventArgs) Handles Button4.Click
    drawPattern = False
    drawBlueRects = True
    Panel1.Refresh()
End Sub

如果我用谷歌搜索到了现成的解决方案，我深表歉意；在这种情况下请提供 link。

此致，

Libor

Answer 1

控件的Invalidate方法指定控件的特定区域需要重绘，Update方法启动重绘。 Refresh方法只是调用了Invalidate，没有参数，说明整个控件需要重新绘制，然后调用Update。不要 Refresh，而是自己调用 Invalidate 和 Update。这样，您可以将适当的参数传递给 Invalidate 以准确指定要重绘控件的哪个或哪些部分。对于一个或多个复杂区域，您可以多次调用 Invalidate。

Answer 2

我通过变通方法解决了这个问题 - 我绘制到位图中并在每次更改时使用该位图更新 PictureBox。由于我可以绘制到位图的特定位置，因此 re-drawing:

没有问题

在 class 标题中定义位图：

Dim bm As New Bitmap(1910, 500)

初始图纸：

Private Sub CreateImage()
    Dim w As Integer = bm.Width ' or PictureBox1.Width
    Dim h As Integer = bm.Height  ' or PictureBox1.Height
    Dim bmp As New Bitmap(w, h, System.Drawing.Imaging.PixelFormat.Format32bppArgb)
    bm = bmp
    Using g As Graphics = Graphics.FromImage(bmp)  ' get it from current state of bitmap
        Me.DoubleBuffered = True
        Dim Ypos As Integer = 0
        Call DrawRecArray(StartY - 100, g, NoOfBaysInSet)
        Call DrawRecArray(StartY + 10, g, NoOfBaysInSet)
        For ic = 0 To icLimit   ' paint middle set of squares
            g.FillRectangle(grayBrush, 5 + ic * 10, StartY + 10, 8, 8)
            Call DrawStringFunc(5 + ic * 10, StartY - 70 + Ypos * 5, ic + 1, g, drawFont)
            Ypos += 1
            If Ypos = 3 Then Ypos = 0
            If Ypos = 1 Then Call DrawStringFunc(5 + ic * 10, StartY - 90 + Ypos * 5, (ic + 1 * 3) / 3, g, drawFontB)
        Next
    End Using
    PictureBox1.Image = bmp  ' put the bitmap into Picturebox !!!
End Sub

更新位图：

Private Sub UpdateImage(FromPos As Int16, ToPos As Int16)
    Dim w As Integer = bm.Width
    Dim h As Integer = bm.Height
    Dim bmp As New Bitmap(Me.PictureBox1.Image) ' now get the bitmap from the PictureBox
    bm = bmp
    Using g As Graphics = Graphics.FromImage(bmp)
        Me.DoubleBuffered = True
        g.FillRectangle(backBrush, 5 + FromPos * 10, StartY + 10, 28, 8)
        g.FillRectangle(grayBrush, 5 + FromPos * 10, StartY + 10, 8, 8)
        g.FillRectangle(grayBrush, 15 + FromPos * 10, StartY + 10, 8, 8)
        g.FillRectangle(grayBrush, 25 + FromPos * 10, StartY + 10, 8, 8)
        g.FillRectangle(blueBrush, 5 + ToPos * 10, StartY + 10, 28, 8)
    End Using
    PictureBox1.Image = bmp  ' update pictureBox with modified bitmap
End Sub

我相信这是一个有价值的答案。我处理 GDI 好几年了，反复遇到这个问题，在成千上万的答案中，只有少数人描述了没有 _paint 事件的重绘，我认为这对这种情况毫无用处。大多数样本是 one-off 图纸。

此致

Libor

只更新部分图形

Update only part of graphics

vb.net

graphics

refresh