如何用Vb.net实现两副图像的上下透明度混合

Question

如何用Vb.net实现两副图像的上下透明度混合

我使用的函数如下：

Public Function OpacityBlend(ByVal BackFile As String, ByVal ForFile As String, ByVal SrcImg As Bitmap, ByVal ForImg As Bitmap,
                             ByVal BackX As Integer, ByVal BackY As Integer, ByVal ForX As Integer,
                            ByVal ForY As Integer, ByVal W As Integer, ByVal H As Integer,
                            Optional ByVal SavePath As String = "", Optional ByVal Opacity As Single = 255) As Bitmap
    Dim Bmp As Bitmap
    If BackFile <> "" Then
        Bmp = Bitmap.FromFile(BackFile)
    Else
        Bmp = SrcImg
    End If
    Dim ForBmp As Bitmap
    If ForFile <> "" Then
        ForBmp = Bitmap.FromFile(ForFile)
    Else
        ForBmp = ForImg
    End If
    Dim BmpDATA As New BitmapData
    Dim TmpBMP As Bitmap = New Bitmap(Bmp)
    Dim Rct As Rectangle = New Rectangle(0, 0, Bmp.Width, Bmp.Height)
    BmpDATA = TmpBMP.LockBits(Rct, ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb)
    Dim BTS(BmpDATA.Stride * BmpDATA.Height) As Byte
    Runtime.InteropServices.Marshal.Copy(BmpDATA.Scan0, BTS, 0, BTS.Length - 1)

    Dim BmpForDATA As New BitmapData
    Dim TmpForBMP As Bitmap = New Bitmap(ForBmp)
    Dim RctFor As Rectangle = New Rectangle(0, 0, ForBmp.Width, ForBmp.Height)
    BmpForDATA = TmpForBMP.LockBits(Rct, ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb)
    Dim BTSFor(BmpForDATA.Stride * BmpForDATA.Height) As Byte
    Runtime.InteropServices.Marshal.Copy(BmpForDATA.Scan0, BTSFor, 0, BTSFor.Length - 1)
    Dim T As Double = 0, x0 As Long, y0 As Long = -1, j As Integer
    j = ForX * 4 * (ForY + 1)
    For i As Integer = 0 To BTS.Length - 4 Step 4
        If x0 = 0 Then y0 = y0 + 1
        x0 = (i / 4) Mod Bmp.Width
        If x0 >= BackX And x0 <= BackX + W Then
            If y0 >= BackY And y0 <= BackY + H Then
                BTS(i) = BlendColor(BTS(i), BTSFor(j), Opacity)
                BTS(i + 1) = BlendColor(BTS(i + 1), BTSFor(j + 1), Opacity)
                BTS(i + 2) = BlendColor(BTS(i + 2), BTSFor(j + 2), Opacity)
            End If
            j = j + 4
        End If
    Next
    Runtime.InteropServices.Marshal.Copy(BTS, 0, BmpDATA.Scan0, BTS.Length - 1)
    TmpBMP.UnlockBits(BmpDATA)
    If SavePath <> "" Then
        Dim Drv As String = SavePath.Substring(0, 1)
        Dim ext As String = IO.Path.GetExtension(SavePath).ToLower
        Dim Path As String = IO.Path.GetDirectoryName(SavePath)
        Do
            On Error Resume Next
            TmpBMP.Save(SavePath)
            If Err.Number = 61 Then
                Shell("explorer.exe " & Path, 1)
                Dim Rc As Integer = MsgBox("目标硬盘" & Drv & "磁盘空间不足，请释放磁盘空间后重试保存！", MsgBoxStyle.Critical + MsgBoxStyle.RetryCancel, "消息")
                If Rc = MsgBoxResult.Cancel Then Exit Do
            End If
        Loop While Err.Number = 61
    End If
    Return TmpBMP
End Function

但是，得到的透明度混合后的图像如图所示，是坏的图像。哪位达人赐教，或者有何其他方法实现两幅图像的透明度混合？

Answer 1

要在 VB.NET 中实现混合具有不同透明度的两个图像的效果，您可以使用 System.Drawing 命名空间在另一个图像上绘制一个图像，并使用 System.Drawing.Imaging.ImageAttributes 调整绘制图像的透明度班级。

以下是如何执行此操作的示例：

' Load the two images into memory
Dim image1 As Image = Image.FromFile("image1.png")
Dim image2 As Image = Image.FromFile("image2.png")

' Create a graphics object for the output image
Dim outputImage As New Bitmap(image1.Width, image1.Height)
Dim graphics As Graphics = Graphics.FromImage(outputImage)

' Set the transparency of the second image
Dim imageAttr As New ImageAttributes()
Dim colorMatrix As New ColorMatrix()
colorMatrix.Matrix33 = 0.5f ' Set the transparency to 50%
imageAttr.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap)

' Draw the first image
graphics.DrawImage(image1, New Rectangle(0, 0, image1.Width, image1.Height), 0, 0, image1.Width, image1.Height, GraphicsUnit.Pixel)

' Draw the second image over the first image
graphics.DrawImage(image2, New Rectangle(0, 0, image2.Width, image2.Height), 0, 0, image2.Width, image2.Height, GraphicsUnit.Pixel, imageAttr)

' Save the output image to a file
outputImage.Save("output.png", ImageFormat.Png)

' Dispose of the graphics object and images
graphics.Dispose()
image1.Dispose()
image2.Dispose()
outputImage.Dispose()

此代码将从文件中加载两个图像，将第二个图像的透明度设置为 50%，并将两个图像绘制在彼此之上，第二个图像绘制在第一个图像上。生成的图像将保存到名为“output.png”的文件中。

请注意，此代码使用 System.Drawing.Imaging.ColorMatrix 类来调整第二个图像的透明度。ColorMatrix 类允许您对图像应用各种颜色变换，例如亮度、对比度和色彩平衡调整。在本例中，我们使用 ColorMatrix 的 Matrix33 属性来设置图像的透明度。值 1.0 表示完全不透明，而值 0.0 表示完全透明。