Die Community zu .NET und Classic VB.

Startseite / Tipps / VB 5/6-Tipp 0687: Grafik mittels GDI+ als PNG speichern

VB 5/6-Tipp 0687: Grafik mittels GDI+ als PNG speichern

 von Frank Schüler

Schwierigkeitsgrad:

Verwendete API-Aufrufe: GdipCreateBitmapFromFile, GdipCreateBitmapFromHBITMAP, GdipCreateHBITMAPFromBitmap, GdipDisposeImage, GdipGetImageEncoders, GdipGetImageEncodersSize, GdipSaveImageToFile, GdiplusShutdown, GdiplusStartup, OleCreatePictureIndirect, lstrcpyW, lstrlenW

Download: Download des Beispielprojektes [5,22 KB]

'Dieser Quellcode stammt von http://www.activevb.de
'und kann frei verwendet werden. Für eventuelle Schäden
'wird nicht gehaftet.

'Um Fehler oder Fragen zu klären, nutzen Sie bitte unser Forum.
'Ansonsten viel Spaß und Erfolg mit diesem Source!

'---------- Anfang Projektdatei GDIPlusSavePNG.vbp ----------
' Die Komponente 'Microsoft Common Dialog Control 6.0 (SP3) (comdlg32.ocx)' wird benötigt.

'--- Anfang Formular "frmGDIPlusSavePNG" alias frmGDIPlusSavePNG.frm  ---
' Steuerelement: Schaltfläche "cmdSaveAsPng"
' Steuerelement: Bildfeld-Steuerelement "Picture1"
' Steuerelement: Standarddialog-Steuerelement "CommonDialog1"
' Steuerelement: Schaltfläche "cmdLoadPicture"

Option Explicit

' ----==== GDI+ Konstanten ====----
Private Const GdiPlusVersion As Long = 1
Private Const mimePNG As String = "image/png"

' ----==== Sonstige Typen ====----
Private Type GUID
    Data1 As Long
    Data2 As Integer
    Data3 As Integer
    Data4(0 To 7) As Byte
End Type

Private Type IID
    Data1 As Long
    Data2 As Integer
    Data3 As Integer
    Data4(0 To 7)  As Byte
End Type

Private Type PICTDESC
    cbSizeOfStruct As Long
    picType As Long
    hgdiObj As Long
    hPalOrXYExt As Long
End Type

' ----==== GDI+ Typen ====----
Private Type ImageCodecInfo
    Clsid As GUID
    FormatID As GUID
    CodecNamePtr As Long
    DllNamePtr As Long
    FormatDescriptionPtr As Long
    FilenameExtensionPtr As Long
    MimeTypePtr As Long
    Flags As Long
    Version As Long
    SigCount As Long
    SigSize As Long
    SigPatternPtr As Long
    SigMaskPtr As Long
End Type

Private Type GdiplusStartupOutput
    NotificationHook As Long
    NotificationUnhook As Long
End Type

Private Type GDIPlusStartupInput
    GdiPlusVersion As Long
    DebugEventCallback As Long
    SuppressBackgroundThread As Long
    SuppressExternalCodecs As Long
End Type

' ----==== GDI+ Enumerationen ====----
' GDI+ Status
Private Enum Status
    OK = 0
    GenericError = 1
    InvalidParameter = 2
    OutOfMemory = 3
    ObjectBusy = 4
    InsufficientBuffer = 5
    NotImplemented = 6
    Win32Error = 7
    WrongState = 8
    Aborted = 9
    FileNotFound = 10
    ValueOverflow = 11
    AccessDenied = 12
    UnknownImageFormat = 13
    FontFamilyNotFound = 14
    FontStyleNotFound = 15
    NotTrueTypeFont = 16
    UnsupportedGdiplusVersion = 17
    GdiplusNotInitialized = 18
    PropertyNotFound = 19
    PropertyNotSupported = 20
    ProfileNotFound = 21
End Enum

' ----==== GDI+ API Deklarationen ====----
Private Declare Function GdipCreateBitmapFromFile Lib "gdiplus" _
    (ByVal FileName As Long, ByRef Bitmap As Long) As Status

Private Declare Function GdipCreateBitmapFromHBITMAP Lib "gdiplus" _
    (ByVal hbm As Long, ByVal hpal As Long, _
    ByRef Bitmap As Long) As Status

Private Declare Function GdipCreateHBITMAPFromBitmap Lib "gdiplus" _
    (ByVal Bitmap As Long, ByRef hbmReturn As Long, _
    ByVal background As Long) As Status

Private Declare Function GdipDisposeImage Lib "gdiplus" _
    (ByVal image As Long) As Status

Private Declare Function GdipGetImageEncoders Lib "gdiplus" _
    (ByVal numEncoders As Long, ByVal Size As Long, _
    ByRef Encoders As Any) As Status

Private Declare Function GdipGetImageEncodersSize Lib "gdiplus" _
    (ByRef numEncoders As Long, ByRef Size As Long) As Status

Private Declare Function GdiplusShutdown Lib "gdiplus" _
    (ByVal token As Long) As Status

Private Declare Function GdiplusStartup Lib "gdiplus" _
    (ByRef token As Long, ByRef lpInput As GDIPlusStartupInput, _
    Optional ByRef lpOutput As Any) As Status

Private Declare Function GdipSaveImageToFile Lib "gdiplus" _
    (ByVal image As Long, ByVal FileName As Long, _
    ByRef clsidEncoder As GUID, _
    ByRef encoderParams As Any) As Status

' ----==== OLE API Deklarationen ====----
Private Declare Sub OleCreatePictureIndirect Lib "oleaut32.dll" _
    (lpPictDesc As PICTDESC, riid As IID, _
    ByVal fOwn As Boolean, lplpvObj As Object)

' ----==== Kernel API Deklarationen ====----
Private Declare Function lstrcpyW Lib "kernel32" _
    (lpString1 As Any, lpString2 As Any) As Long

Private Declare Function lstrlenW Lib "kernel32" _
    (lpString As Any) As Long

' ----==== Variablen ====----
Dim GdipToken As Long
Dim GdipInitialized As Boolean

'------------------------------------------------------
' Funktion     : Execute
' Beschreibung : Gibt im Fehlerfall die entsprechende
'                GDI+ Fehlermeldung aus
' Übergabewert : GDI+ Status
' Rückgabewert : GDI+ Status
'------------------------------------------------------
Private Function Execute(ByVal lReturn As Status) As Status
    Dim lCurErr As Status
    If lReturn = Status.OK Then
        lCurErr = Status.OK
    Else
        lCurErr = lReturn
        MsgBox GdiErrorString(lReturn) & " GDI+ Error:" _
        & lReturn, vbOKOnly, "GDI Error"
    End If
    Execute = lCurErr
End Function

'------------------------------------------------------
' Funktion     : GdiErrorString
' Beschreibung : Umwandlung der GDI+ Statuscodes in Stringcodes
' Übergabewert : GDI+ Status
' Rückgabewert : Fehlercode als String
'------------------------------------------------------
Private Function GdiErrorString(ByVal lError As Status) As String
    Dim s As String
    
    Select Case lError
    Case GenericError:              s = "Generic Error."
    Case InvalidParameter:          s = "Invalid Parameter."
    Case OutOfMemory:               s = "Out Of Memory."
    Case ObjectBusy:                s = "Object Busy."
    Case InsufficientBuffer:        s = "Insufficient Buffer."
    Case NotImplemented:            s = "Not Implemented."
    Case Win32Error:                s = "Win32 Error."
    Case WrongState:                s = "Wrong State."
    Case Aborted:                   s = "Aborted."
    Case FileNotFound:              s = "File Not Found."
    Case ValueOverflow:             s = "Value Overflow."
    Case AccessDenied:              s = "Access Denied."
    Case UnknownImageFormat:        s = "Unknown Image Format."
    Case FontFamilyNotFound:        s = "FontFamily Not Found."
    Case FontStyleNotFound:         s = "FontStyle Not Found."
    Case NotTrueTypeFont:           s = "Not TrueType Font."
    Case UnsupportedGdiplusVersion: s = "Unsupported Gdiplus Version."
    Case GdiplusNotInitialized:     s = "Gdiplus Not Initialized."
    Case PropertyNotFound:          s = "Property Not Found."
    Case PropertyNotSupported:      s = "Property Not Supported."
    Case Else:                      s = "Unknown GDI+ Error."
    End Select
    
    GdiErrorString = s
End Function

'------------------------------------------------------
' Funktion     : GetEncoderClsid
' Beschreibung : Ermittelt die Clsid des Encoders
' Übergabewert : mimeType = mimeType des Encoders
'                pClsid = CLSID des Encoders (in/out)
' Rückgabewert : True = Ermitteln erfolgreich
'                False = Ermitteln fehlgeschlagen
'------------------------------------------------------
Private Function GetEncoderClsid(mimeType As String, _
    pClsid As GUID) As Boolean
    
    Dim num As Long
    Dim Size As Long
    Dim pImageCodecInfo() As ImageCodecInfo
    Dim j As Long
    Dim buffer As String
    
    Call GdipGetImageEncodersSize(num, Size)
    If (Size = 0) Then
        ' fehlgeschlagen
        GetEncoderClsid = False
        Exit Function
    End If
    
    ReDim pImageCodecInfo(0 To Size \ Len(pImageCodecInfo(0)) - 1)
    
    Call GdipGetImageEncoders(num, Size, pImageCodecInfo(0))
    
    For j = 0 To num - 1
        
        buffer = _
        Space$(lstrlenW(ByVal pImageCodecInfo(j).MimeTypePtr))
        
        Call lstrcpyW(ByVal StrPtr(buffer), _
        ByVal pImageCodecInfo(j).MimeTypePtr)
        
        If (StrComp(buffer, mimeType, vbTextCompare) = 0) Then
            pClsid = pImageCodecInfo(j).Clsid
            Erase pImageCodecInfo
            ' erfolgreich
            GetEncoderClsid = True
            Exit Function
        End If
    Next j
    
    Erase pImageCodecInfo
    ' fehlgeschlagen
    GetEncoderClsid = False
End Function

'------------------------------------------------------
' Funktion     : HandleToPicture
' Beschreibung : Umwandeln eines Bitmap Handle
'                in ein StdPicture Objekt
' Übergabewert : hGDIHandle = Bitmap Handle
'                ObjectType = Bitmaptyp
' Rückgabewert : StdPicture Objekt
'------------------------------------------------------
Private Function HandleToPicture(ByVal hGDIHandle As Long, _
    ByVal ObjectType As PictureTypeConstants, _
    Optional ByVal hpal As Long = 0) As StdPicture
    
    Dim tPictDesc As PICTDESC
    Dim IID_IPicture As IID
    Dim oPicture As IPicture
    
    ' Initialisiert die PICTDESC Structur
    With tPictDesc
        .cbSizeOfStruct = Len(tPictDesc)
        .picType = ObjectType
        .hgdiObj = hGDIHandle
        .hPalOrXYExt = hpal
    End With
    
    ' Initialisiert das IPicture Interface ID
    With IID_IPicture
        .Data1 = &H7BF80981
        .Data2 = &HBF32
        .Data3 = &H101A
        .Data4(0) = &H8B
        .Data4(1) = &HBB
        .Data4(3) = &HAA
        .Data4(5) = &H30
        .Data4(6) = &HC
        .Data4(7) = &HAB
    End With
    
    ' Erzeugen des Objekts
    OleCreatePictureIndirect tPictDesc, IID_IPicture, _
    True, oPicture
    
    ' Rückgabe des Pictureobjekts
    Set HandleToPicture = oPicture
    
End Function

'------------------------------------------------------
' Funktion     : LoadPicturePlus
' Beschreibung : Lädt ein Bilddatei per GDI+
' Übergabewert : Pfad\Dateiname der Bilddatei
' Rückgabewert : StdPicture Objekt
'------------------------------------------------------
Public Function LoadPicturePlus( _
    ByVal sFileName As String) As StdPicture
    
    Dim lBitmap As Long
    Dim hBitmap As Long
    
    ' Öffnet die Bilddatei in lBitmap
    If Execute(GdipCreateBitmapFromFile(StrPtr(sFileName), _
    lBitmap)) = OK Then
        
        ' Handle der Bitmap ermitteln lBitmap -> hBitmap
        If Execute(GdipCreateHBITMAPFromBitmap(lBitmap, _
        hBitmap, 0)) = OK Then
            
            ' Erzeugen des StdPicture Objekts von hBitmap
            Set LoadPicturePlus = HandleToPicture(hBitmap, _
            vbPicTypeBitmap)
        End If
        
        ' Lösche lBitmap
        Call Execute(GdipDisposeImage(lBitmap))
        
    End If
End Function

'------------------------------------------------------
' Funktion     : SavePictureAsPNG
' Beschreibung : Speichert ein StdPicture Objekt
'                per GDI+ als PNG
' Übergabewert : Pic = StdPicture Objekt
'                FileName = Pfad\Dateiname.png
' Rückgabewert : True = speichern erfolgreich
'                False = speichern fehlgeschlagen
'------------------------------------------------------
Private Function SavePictureAsPNG(ByVal Pic As StdPicture, _
    ByVal sFileName As String) As Boolean
    
    Dim lBitmap As Long
    Dim tPicEncoder As GUID
    
    ' Erzeugt eine GDI+ Bitmap vom
    ' StdPicture Handle -> lBitmap
    If Execute(GdipCreateBitmapFromHBITMAP( _
    Pic.Handle, 0, lBitmap)) = OK Then
        
        ' Ermitteln der CLSID vom mimeType Encoder
        If GetEncoderClsid(mimePNG, tPicEncoder) = True Then
            
            ' Speichert lBitmap als PNG
            If Execute(GdipSaveImageToFile(lBitmap, _
            StrPtr(sFileName), tPicEncoder, ByVal 0)) = OK Then
                
                ' speichern erfolgreich
                SavePictureAsPNG = True
            Else
                ' speichern nicht erfolgreich
                SavePictureAsPNG = False
            End If
        Else
            ' speichern nicht erfolgreich
            SavePictureAsPNG = False
            MsgBox "Konnte keinen passenden Encoder ermitteln.", _
            vbOKOnly, "Encoder Error"
        End If
        
        ' Lösche lBitmap
        Call Execute(GdipDisposeImage(lBitmap))
        
    End If
End Function

'------------------------------------------------------
' Funktion     : StartUpGDIPlus
' Beschreibung : Initialisiert GDI+ Instanz
' Übergabewert : GDI+ Version
' Rückgabewert : GDI+ Status
'------------------------------------------------------
Private Function StartUpGDIPlus(ByVal GdipVersion As Long) As Status
    ' Initialisieren der GDI+ Instanz
    Dim tGdipStartupInput As GDIPlusStartupInput
    Dim tGdipStartupOutput As GdiplusStartupOutput
    
    tGdipStartupInput.GdiPlusVersion = GdipVersion
    StartUpGDIPlus = GdiplusStartup(GdipToken, _
    tGdipStartupInput, tGdipStartupOutput)
End Function

'------------------------------------------------------
' Funktion     : ShutDownGDIPlus
' Beschreibung : Beendet die GDI+ Instanz
' Rückgabewert : GDI+ Status
'------------------------------------------------------
Private Function ShutDownGDIPlus() As Status
    ' Beendet GDI+ Instanz
    ShutDownGDIPlus = GdiplusShutdown(GdipToken)
End Function

'------------------------------------------------------
' Beschreibung : Bilddatei laden
'------------------------------------------------------
Private Sub cmdLoadPicture_Click()
    
    ' Fehlerbehandlung
    On Error Goto errorhandler
    
    ' ist GDI+ Initialisiert
    If GdipInitialized = True Then
        
        ' Dialogparameter setzen
        With CommonDialog1
            .Filter = "Images Files (*.bmp;*.gif;*.jpg;*.png;*.tif)" _
            & "|*.bmp;*.gif;*.jpg;*.png;*.tif"
            .CancelError = True
            .ShowOpen
        End With
        
        ' Bild per GDI+ laden und anzeigen
        Picture1.Picture = _
        LoadPicturePlus(CommonDialog1.FileName)
        
        ' Button aktivieren, wenn ein Bild geladen ist
        If Not Picture1.Picture Is Nothing _
        Then cmdSaveAsPng.Enabled = True
    End If
    
    Exit Sub
errorhandler:
End Sub

'------------------------------------------------------
' Beschreibung : Bilddatei speichern
'------------------------------------------------------
Private Sub cmdSaveAsPng_Click()
    
    ' Fehlerbehandlung
    On Error Goto errorhandler
    
    ' ist GDI+ Initialisiert
    If GdipInitialized = True Then
        
        ' Dialogparameter setzen
        With CommonDialog1
            .Filter = "Images Files (*.png)|*.png"
            .FileName = "*.png"
            .CancelError = True
            .Flags = cdlOFNOverwritePrompt
            .ShowSave
        End With
        
        ' Bild als PNG-Datei speichern
        If SavePictureAsPNG(Picture1, _
        CommonDialog1.FileName) = False Then
            
            ' im Fehlerfall, Meldung ausgeben
            MsgBox "Speichern ist fehlgeschlagen.", _
            vbOKOnly, "Error"
        End If
    End If
    
    Exit Sub
errorhandler:
End Sub

'------------------------------------------------------
' Beschreibung : Form laden
'------------------------------------------------------
Private Sub Form_Load()
    
    GdipInitialized = False
    
    ' GDI+ initialisieren
    If Execute(StartUpGDIPlus(GdiPlusVersion)) = OK Then
        GdipInitialized = True
    Else
        MsgBox "GDI+ not inizialized.", vbOKOnly, "GDI Error"
    End If
    
    ' Button deaktivieren
    cmdSaveAsPng.Enabled = False
End Sub

'------------------------------------------------------
' Beschreibung : Form entladen
'------------------------------------------------------
Private Sub Form_Unload(Cancel As Integer)
    
    ' ist GDI+ Initialisiert
    If GdipInitialized = True Then
        
        ' GDI+ beenden
        Call Execute(ShutDownGDIPlus)
    End If
End Sub
'--- Ende Formular "frmGDIPlusSavePNG" alias frmGDIPlusSavePNG.frm  ---
'----------- Ende Projektdatei GDIPlusSavePNG.vbp -----------