关于VB6中代码显示PNG图片的问题
vb6中显示png图片，主要代码来自于帖子
http://www.vbforums.com/showthread.php?509292-RESOLVED-png-files-in-Visual-Basic中的【Using_Ping_In_VB.ZIP】例子。
本人对【Using_Ping_In_VB.ZIP】的代码做了相关修改以适应本人要求。具体代码见下面
1. modGDIPlusResize.bas
Option Explicit
Private Type GUID
Data1 As Long
Data2 As Integer
Data3 As Integer
Data4(7) As Byte
End Type
Private Type PICTDESC
size As Long
Type As Long
hBmp As Long
hPal As Long
Reserved As Long
End Type
Private Type GdiplusStartupInput
GdiplusVersion As Long
DebugEventCallback As Long
SuppressBackgroundThread As Long
SuppressExternalCodecs As Long
End Type
Private Type PWMFRect16
left As Integer
top As Integer
Right As Integer
Bottom As Integer
End Type
Private Type wmfPlaceableFileHeader
Key As Long
hMf As Integer
BoundingBox As PWMFRect16
Inch As Integer
Reserved As Long
CheckSum As Integer
End Type
' GDI Functions
Private Declare Function CreateCompatibleDC Lib "gdi32" (ByVal hDC As Long) As Long
Private Declare Function OleCreatePictureIndirect Lib "olepro32.dll" (PicDesc As PICTDESC, RefIID As GUID, ByVal fPictureOwnsHandle As Long, IPic As IPicture) As Long
Private Declare Function CreateCompatibleBitmap Lib "gdi32" (ByVal hDC As Long, ByVal nWidth As Long, ByVal nHeight As Long) As Long
Private Declare Function GetDeviceCaps Lib "gdi32" (ByVal hDC As Long, ByVal nIndex As Long) As Long
Private Declare Function PatBlt Lib "gdi32" (ByVal hDC As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal dwRop As Long) As Long
Private Declare Function CreateBitmap Lib "gdi32" (ByVal nWidth As Long, ByVal nHeight As Long, ByVal nPlanes As Long, ByVal nBitCount As Long, lpBits As Any) As Long
Private Declare Function SelectObject Lib "gdi32" (ByVal hDC As Long, ByVal hObject As Long) As Long
Private Declare Function CreateSolidBrush Lib "gdi32" (ByVal crColor As Long) As Long
Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
Private Declare Function DeleteDC Lib "gdi32" (ByVal hDC As Long) As Long
' GDI+ functions
Private Declare Function GdipLoadImageFromFile Lib "gdiplus.dll" (ByVal FileName As Long, GpImage As Long) As Long
Private Declare Function GdiplusStartup Lib "gdiplus.dll" (Token As Long, gdipInput As GdiplusStartupInput, GdiplusStartupOutput As Long) As Long
Private Declare Function GdipCreateFromHDC Lib "gdiplus.dll" (ByVal hDC As Long, GpGraphics As Long) As Long
Private Declare Function GdipSetInterpolationMode Lib "gdiplus.dll" (ByVal Graphics As Long, ByVal InterMode As Long) As Long
Private Declare Function GdipDrawImageRectI Lib "gdiplus.dll" (ByVal Graphics As Long, ByVal Img As Long, ByVal x As Long, ByVal y As Long, ByVal Width As Long, ByVal Height As Long) As Long
Private Declare Function GdipDeleteGraphics Lib "gdiplus.dll" (ByVal Graphics As Long) As Long
Private Declare Function GdipDisposeImage Lib "gdiplus.dll" (ByVal Image As Long) As Long
Private Declare Function GdipCreateBitmapFromHBITMAP Lib "gdiplus.dll" (ByVal hBmp As Long, ByVal hPal As Long, GpBitmap As Long) As Long
Private Declare Function GdipGetImageWidth Lib "gdiplus.dll" (ByVal Image As Long, Width As Long) As Long
Private Declare Function GdipGetImageHeight Lib "gdiplus.dll" (ByVal Image As Long, Height As Long) As Long
Private Declare Function GdipCreateMetafileFromWmf Lib "gdiplus.dll" (ByVal hWmf As Long, ByVal deleteWmf As Long, WmfHeader As wmfPlaceableFileHeader, Metafile As Long) As Long
Private Declare Function GdipCreateMetafileFromEmf Lib "gdiplus.dll" (ByVal hEmf As Long, ByVal deleteEmf As Long, Metafile As Long) As Long
Private Declare Function GdipCreateBitmapFromHICON Lib "gdiplus.dll" (ByVal hIcon As Long, GpBitmap As Long) As Long
Private Declare Function GdipDrawImageRectRectI Lib "gdiplus.dll" (ByVal Graphics As Long, ByVal GpImage As Long, ByVal dstx As Long, ByVal dsty As Long, ByVal dstwidth As Long, ByVal dstheight As Long, ByVal srcx As Long, ByVal srcy As Long, ByVal srcwidth As Long, ByVal srcheight As Long, ByVal srcUnit As Long, ByVal imageAttributes As Long, ByVal callback As Long, ByVal callbackData As Long) As Long
Private Declare Sub GdiplusShutdown Lib "gdiplus.dll" (ByVal Token As Long)
' GDI and GDI+ constants
Private Const PLANES = 14 ' Number of planes
Private Const BITSPIXEL = 12 ' Number of bits per pixel
Private Const PATCOPY = &HF00021 ' (DWORD) dest = pattern
Private Const PICTYPE_BITMAP = 1 ' Bitmap type
Private Const InterpolationModeHighQualityBicubic = 7
Private Const GDIP_WMF_PLACEABLEKEY = &H9AC6CDD7
Private Const UnitPixel = 2
' Initialises GDI Plus
Public Function InitGDIPlus() As Long
Dim Token As Long
Dim gdipInit As GdiplusStartupInput
gdipInit.GdiplusVersion = 1
GdiplusStartup Token, gdipInit, ByVal 0&
InitGDIPlus = Token
End Function
' Frees GDI Plus
Public Sub FreeGDIPlus(Token As Long)
GdiplusShutdown Token
End Sub
' Loads the picture (optionally resized)
Public Function LoadPictureGDIPlus(PicFile As String, Optional Width As Long = -1, Optional Height As Long = -1, Optional ByVal BackColor As Long = vbWhite, Optional RetainRatio As Boolean = False) As IPicture
Dim hDC As Long
Dim hBitmap As Long
Dim Img As Long
' Load the image
If GdipLoadImageFromFile(StrPtr(PicFile), Img) <> 0 Then
Err.Raise 999, "GDI+ Module", "Error loading picture " & PicFile
Exit Function
End If
' Calculate picture's width and height if not specified
If Width = -1 Or Height = -1 Then
GdipGetImageWidth Img, Width
GdipGetImageHeight Img, Height
End If
' Initialise the hDC
InitDC hDC, hBitmap, BackColor, Width, Height
' Resize the picture
gdipResize Img, hDC, Width, Height, RetainRatio
GdipDisposeImage Img
' Get the bitmap back
GetBitmap hDC, hBitmap
' Create the picture
Set LoadPictureGDIPlus = CreatePicture(hBitmap)
End Function
' Initialises the hDC to draw
Private Sub InitDC(hDC As Long, hBitmap As Long, BackColor As Long, Width As Long, Height As Long)
Dim hBrush As Long
' Create a memory DC and select a bitmap into it, fill it in with the backcolor
hDC = CreateCompatibleDC(ByVal 0&)
hBitmap = CreateBitmap(Width, Height, GetDeviceCaps(hDC, PLANES), GetDeviceCaps(hDC, BITSPIXEL), ByVal 0&)
hBitmap = SelectObject(hDC, hBitmap)
hBrush = CreateSolidBrush(BackColor)
hBrush = SelectObject(hDC, hBrush)
PatBlt hDC, 0, 0, Width, Height, PATCOPY
DeleteObject SelectObject(hDC, hBrush)
End Sub
' Resize the picture using GDI plus
Private Sub gdipResize(Img As Long, hDC As Long, Width As Long, Height As Long, Optional RetainRatio As Boolean = False)
Dim Graphics As Long ' Graphics Object Pointer
Dim OrWidth As Long ' Original Image Width
Dim OrHeight As Long ' Original Image Height
Dim OrRatio As Double ' Original Image Ratio
Dim DesRatio As Double ' Destination rect Ratio
Dim DestX As Long ' Destination image X
Dim DestY As Long ' Destination image Y
Dim DestWidth As Long ' Destination image Width
Dim DestHeight As Long ' Destination image Height
GdipCreateFromHDC hDC, Graphics
GdipSetInterpolationMode Graphics, InterpolationModeHighQualityBicubic
If RetainRatio Then
GdipGetImageWidth Img, OrWidth
GdipGetImageHeight Img, OrHeight
OrRatio = OrWidth / OrHeight
DesRatio = Width / Height
' Calculate destination coordinates
DestWidth = IIf(DesRatio < OrRatio, Width, Height * OrRatio)
DestHeight = IIf(DesRatio < OrRatio, Width / OrRatio, Height)
' DestX = (Width - DestWidth) / 2
' DestY = (Height - DestHeight) / 2
DestX = 0
DestY = 0
GdipDrawImageRectRectI Graphics, Img, DestX, DestY, DestWidth, DestHeight, 0, 0, OrWidth, OrHeight, UnitPixel, 0, 0, 0
Else
GdipDrawImageRectI Graphics, Img, 0, 0, Width, Height
End If
GdipDeleteGraphics Graphics
End Sub
' Replaces the old bitmap of the hDC, Returns the bitmap and Deletes the hDC
Private Sub GetBitmap(hDC As Long, hBitmap As Long)
hBitmap = SelectObject(hDC, hBitmap)
DeleteDC hDC
End Sub
' Creates a Picture Object from a handle to a bitmap
Private Function CreatePicture(hBitmap As Long) As IPicture
Dim IID_IDispatch As GUID
Dim Pic As PICTDESC
Dim IPic As IPicture
' Fill in OLE IDispatch Interface ID
IID_IDispatch.Data1 = &H20400
IID_IDispatch.Data4(0) = &HC0
IID_IDispatch.Data4(7) = &H46
' Fill Pic with necessary parts
Pic.size = Len(Pic) ' Length of structure
Pic.Type = PICTYPE_BITMAP ' Type of Picture (bitmap)
Pic.hBmp = hBitmap ' Handle to bitmap
' Create the picture
OleCreatePictureIndirect Pic, IID_IDispatch, True, IPic
Set CreatePicture = IPic
End Function
' Returns a resized version of the picture
Public Function Resize(Handle As Long, PicType As PictureTypeConstants, Width As Long, Height As Long, Optional BackColor As Long = vbWhite, Optional RetainRatio As Boolean = False) As IPicture
Dim Img As Long
Dim hDC As Long
Dim hBitmap As Long
Dim WmfHeader As wmfPlaceableFileHeader
' Determine pictyre type
Select Case PicType
Case vbPicTypeBitmap
GdipCreateBitmapFromHBITMAP Handle, ByVal 0&, Img
Case vbPicTypeMetafile
FillInWmfHeader WmfHeader, Width, Height
GdipCreateMetafileFromWmf Handle, False, WmfHeader, Img
Case vbPicTypeEMetafile
GdipCreateMetafileFromEmf Handle, False, Img
Case vbPicTypeIcon
' Does not return a valid Image object
GdipCreateBitmapFromHICON Handle, Img
End Select
' Continue with resizing only if we have a valid image object
If Img Then
InitDC hDC, hBitmap, BackColor, Width, Height
gdipResize Img, hDC, Width, Height, RetainRatio
GdipDisposeImage Img
GetBitmap hDC, hBitmap
Set Resize = CreatePicture(hBitmap)
End If
End Function
' Fills in the wmfPlacable header
Private Sub FillInWmfHeader(WmfHeader As wmfPlaceableFileHeader, Width As Long, Height As Long)
WmfHeader.BoundingBox.Right = Width
WmfHeader.BoundingBox.Bottom = Height
WmfHeader.Inch = 1440
WmfHeader.Key = GDIP_WMF_PLACEABLEKEY
End Sub
2. 调用Form1.frm
Private Declare Function GetSysColor Lib "user32" (ByVal nIndex As Long) As Long
Private Sub Command1_Click()
Dim Token As Long
Dim C As Double
Dim i As Integer
C = Me.BackColor
If C < 0 Then C = GetSysColor(C - &H80000000)
Token = InitGDIPlus
Picture1(0).Picture = LoadPictureGDIPlus(App.Path & "\1.png", , , vbWhite)
Picture1(1).Picture = LoadPictureGDIPlus(App.Path & "\1.png", , , vbCyan)
Picture1(2).Picture = LoadPictureGDIPlus(App.Path & "\1.png", , , vbGreen)
Picture1(3).Picture = LoadPictureGDIPlus(App.Path & "\1.png", , , C)
FreeGDIPlus Token
End Sub主要代码改动说明
1. Dim C As Long 修改为 Dim C As Double (因Long类型数据范围不能满足存储color数据的需要，所以将变量C的数据类型改为Double，以便于存储color数据，如果不做修改，程序在调试时可正常运行，但在编译后运行会出现数据溢出的问题)，long类型与double类型的数据范围可自行查找vb数据类型资料来进行相关比较。
2. Picture1(0).AutoSize 属性设计时改为True，当然也可在运行时通过代码实现。(因LoadPictureGDIPlus函数根据png图片的大小来进行透明处理，如果png图片大小比Picture1控件小，那么png图片与Picture1控件之间的区域将不能被透明处理)。有兴趣的朋友可进行相关测试查看效果。
下面为效果图
