VB利用GDI+显示PNG图像

所属类别：VB
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发布日期：2007-7-20

在VB使用PNG透明格式的图片其实是非常容易的，那就是使用XP以上操作系统中的GDI+库：

需要声明的GDI+的函数：
    Private Declare Function GdiplusStartup Lib "gdiplus.dll" ( _
    ByRef token As Long, _
    ByRef inputX As GdiplusStartupInput, _
    ByVal Output As Long _
    ) As Status

    Private Declare Sub GdiplusShutdown Lib "gdiplus.dll" (ByVal token As Long)

    Private Declare Function GdipCreateFromHDC Lib "gdiplus.dll" ( _
    ByVal hdc As Long, ByRef graphics As Long _
    ) As Status


    Private Declare Function GdipDrawImage Lib "gdiplus.dll" ( _
    ByVal graphics As Long, ByVal Image As Long, _
    ByVal X As Single, ByVal Y As Single _
    ) As Status

    Private Declare Function GdipLoadImageFromFile Lib "gdiplus.dll" ( _
    ByVal FileName As Long, ByRef Image As Long _
    ) As Status

Private Declare Function GdipDisposeImage Lib "gdiplus.dll" _
    (ByVal Image As Long) As Status

需要声明的结构：

    Private Type GdiplusStartupInput
    GdiplusVersion As Long
    DebugEventCallback As Long
    SuppressBackgroundThread As Long
    SuppressExternalCodecs As Long
    End Type

具体做法如下：

    Dim m_lngGraphics as long
    Dim m_lngInstance as long
    Dim m_lngPic as long

    Private Sub Form_Load() 'GDI+初始化
    Dim udtData As GdiplusStartupInput

    Randomize

    udtData.GdiplusVersion = 1

    If GdiplusStartup(app.hInstance, udtData, 0) Then
        MsgBox "GDI+ could not be initialized", vbCritical
        Exit Sub
    End If

    If GdipCreateFromHDC(Me.hdc, m_lngGraphics) Then
        MsgBox "Graphics object could not be created", vbCritical
        Exit Sub
    End If

GdipLoadimagefromfile "c:\1.png" , m_lngPic
GdipImageDraw m_lngGraphics,m_lngPic
End Sub