VB6 GDI 图像扩边代码

VB6中可以使用GDI（图形设备接口）来进行图像扩边操作。下面是一个简单的示例代码，用于在VB6中实现图像扩边：

Private Declare Function CreateCompatibleDC Lib "gdi32" (ByVal hdc As Long) As Long
Private Declare Function SelectObject Lib "gdi32" (ByVal hdc As Long, ByVal hObject As Long) As Long
Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
Private Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal dwRop As Long) As Long
Private Declare Function GetDeviceCaps Lib "gdi32" (ByVal hdc As Long, ByVal nIndex As Long) As Long

Private Const SRCCOPY = &HCC0020
Private Const HORZRES = 8
Private Const VERTRES = 10

Public Sub ExpandImageBorder(ByVal srcImage As PictureBox, ByVal borderWidth As Integer)
    Dim srcHDC As Long
    Dim srcBitmap As Long
    Dim srcWidth As Long
    Dim srcHeight As Long
    
    ' 获取源图像的句柄和尺寸
    srcHDC = CreateCompatibleDC(0)
    srcBitmap = SelectObject(srcHDC, srcImage.Image)
    srcWidth = srcImage.ScaleWidth
    srcHeight = srcImage.ScaleHeight
    
    ' 创建新的位图，用于扩边后的图像
    Dim newWidth As Long
    Dim newHeight As Long
    newWidth = srcWidth + borderWidth * 2
    newHeight = srcHeight + borderWidth * 2
    Dim newBitmap As Long
    newBitmap = CreateCompatibleBitmap(srcHDC, newWidth, newHeight)
    
    ' 创建新的设备上下文，用于绘制扩边后的图像
    Dim newHDC As Long
    newHDC = CreateCompatibleDC(0)
    SelectObject newHDC, newBitmap
    
    ' 设置背景颜色为白色
    Dim oldBrush As Long
    oldBrush = SelectObject(newHDC, GetStockObject(WHITE_BRUSH))
    PatBlt newHDC, 0, 0, newWidth, newHeight, PATCOPY
    
    ' 计算扩边后的图像在新位图中的位置
    Dim destX As Long
    Dim destY As Long
    destX = borderWidth
    destY = borderWidth
    
    ' 将源图像复制到新位图中，实现扩边效果
    BitBlt newHDC, destX, destY, srcWidth, srcHeight, srcHDC, 0, 0, SRCCOPY
    
    ' 将扩边后的图像显示在PictureBox控件中
    srcImage.Picture = newBitmap
    
    ' 清理资源
    SelectObject srcHDC, srcBitmap
    DeleteObject srcBitmap
    DeleteObject newBitmap
    DeleteObject oldBrush
End Sub

使用以上代码，你可以通过调用`ExpandImageBorder`方法来实现图像的扩边。该方法接受两个参数：`srcImage`为要进行扩边的PictureBox控件，`borderWidth`为要扩展的边框宽度。

注意：以上代码仅为示例，实际使用时需要根据具体情况进行适当的修改和调整。