c# - 从位图数组创建大位图的快速方法？

Question

我有这个代码，

复制/粘贴到新的winform应用程序中，如果运行它，这将在桌面上写入一个文件:test123abcd.png

Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
    Dim SquareSize = 5
    Dim GridX = 2500
    Dim GridY = 2500
    Dim SquareCount = GridX * GridY - 1
    Dim sw As New Stopwatch

    Dim Rect(4) As Rectangle
    Rect(0) = New Rectangle(0, 3, 3, 1)
    Rect(1) = New Rectangle(3, 0, 1, 3)
    Rect(2) = New Rectangle(3, 3, 3, 1)
    Rect(3) = New Rectangle(0, 0, 1, 3)

    Dim fullsw = Stopwatch.StartNew
    Using board = New Bitmap(SquareSize * (GridX + 1), SquareSize * (GridY + 1), Imaging.PixelFormat.Format32bppPArgb)
        Using graph = Graphics.FromImage(board)
            Using _board = New Bitmap(SquareSize, SquareSize, Imaging.PixelFormat.Format32bppPArgb)
                Using g As Graphics = Graphics.FromImage(_board)
                    For i = 0 To SquareCount
                        g.Clear(If((i And 1) = 1, Color.Red, Color.Blue))
                        g.FillRectangles(Brushes.White, Rect)
                        sw.Start()
                        graph.DrawImageUnscaled(_board, ((i Mod GridX) * SquareSize), ((i \ GridY) * SquareSize))
                        sw.Stop()
                    Next
                End Using
            End Using
        End Using
        fullsw.Stop()
        board.Save(Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory) & "\test123abcd.png", Imaging.ImageFormat.Png)
    End Using

    MessageBox.Show("Full SW: " & fullsw.ElapsedMilliseconds & Environment.NewLine &
                    "DrawImageUnscaled SW: " & sw.ElapsedMilliseconds)
End Sub

大约 40% 到 45% 的时间花在 DrawImageUnscaled 上，在我当前的计算机上大约需要 23 秒，而整个过程大约需要 50 秒

有没有办法加快DrawImageUnscaled的速度？ (也许是整个事情？)

编辑 - vb.net 中的问题，c# 中的答案

Answer 1

假设生成部分(g.FillRectangles(Brushes.White, Rect)，也相当耗时)无法避免，您能做的最好的事情就是避免第二个图表 -生成过程(也适用于 board)，只需从 _board 复制信息。复制比新一代要快得多(如下所示)，但是您会遇到源信息(_board)与目标格式(board)不匹配的问题，通过依赖.SetPixel)，因此您必须创建一个函数，根据提供的信息(当前矩形)确定当前像素(X/Y 点)。

下面您可以看到一个简单的代码，显示两种方法之间的时间要求差异:

Dim SquareSize As Integer = 5
Dim _board As Bitmap = Bitmap.FromFile("in.png")
Dim board As Bitmap = New Bitmap(_board.Width * SquareSize, _board.Height * SquareSize)

For x As Integer = 0 To _board.Width - 1
    For y As Integer = 0 To _board.Height - 1
        board.SetPixel(x * SquareSize, y * SquareSize, _board.GetPixel(x, y))
    Next
Next

board.Save("out1.png", Imaging.ImageFormat.Png)


board = New Bitmap(_board.Width, _board.Height)

Using board
    Using graph = Graphics.FromImage(board)
        Using _board
            Using g As Graphics = Graphics.FromImage(_board)
                For x As Integer = 0 To _board.Width - 1
                    For y As Integer = 0 To _board.Height - 1
                        graph.DrawImageUnscaled(_board, x, y)
                    Next
                Next
            End Using
        End Using
    End Using
    board.Save("out2.png", Imaging.ImageFormat.Png)
End Using

请记住，它不是“正常工作的代码”。它的重点是展示如何在位图之间复制像素(通过乘以一个因子，只是为了获得与输入不同的输出)；并将 DrawImageUnscaled 方法置于同等条件下(尽管输出图片在逻辑上是不同的)，以便更好地了解两种方法之间的时间要求差异。

正如评论中所说，这是我在当前条件下所能做的。我希望这足以帮助您找到最佳解决方案。