[vb6] Class to make Image Controls Support PNG, TIF, GIF Animation

[LaVolpe]

You have to use the actual height along with the srcY for partial renderring

Using pixels for example. Let's say the image was 300 pixels in height and you wanted to render 200 of the 300
SrcY = ActualHeight - SrcY i.e., SrcY = 300 - 200

I see you have this in a class and are manually converting to/from himetrics. But I'll use ScaleX & ScaleY for easier reading & assume all the parameters are passed in pixels.

.Render (hDC), destX, destY, destWidth, destHeight, _
    srcX, .Height - ScaleY(SrcY, vbPixels, vbHimetric), SrcWidth, -SrcHeight, ByVal 0&

To prevent unexpected consequences, I'd recommend validating passed source parameters at a minimum & also ensure destination parameters are within reason. Maybe one of the following proves invalid?
- SrcY + SrcHeight cannot be less than 0 and cannot be > ActualHeight
- SrcX + SrcWidth cannot be less than 0 and cannot be > ActualWidth
- SrcHeight & SrcWidth must be between 0 and actual dimensions

[Jonney]

You have to use the actual height along with the srcY for partial renderring

Using pixels for example. Let's say the image was 300 pixels in height and you wanted to render 200 of the 300
SrcY = ActualHeight - SrcY i.e., SrcY = 300 - 200

I see you have this in a class and are manually converting to/from himetrics. But I'll use ScaleX & ScaleY for easier reading & assume all the parameters are passed in pixels.

.Render (hDC), destX, destY, destWidth, destHeight, _
    srcX, .Height - ScaleY(SrcY, vbPixels, vbHimetric), SrcWidth, -SrcHeight, ByVal 0&

The above code is the same with #27.
I want to Render stdPicture on a Grid Cell, the Cell has 16 types of alignments, from what I tested, implement Vertical partial paint has difficulties. For example, I want to paint "RightBottom"(or LeftBottom or CenterBottom), With Cell height reducing, the picture should moving up as well, until Top of picture is covered. With the above code, if the cell height is smaller than picture actual height, the picture just disappear. I have tried many combinations, but still hard to do so,though my GDI+ render code works for all scenarios.

Public Enum AlignmentEnum

    GeneralGeneral = 0 'Horizontal Default; Vertical Default. 'Left Center
    GeneralTop = 1 'Horizontal Default; Vertical Top.         'Left Top
    GeneralCenter = 2 'Horizontal Default; Vertical Center.   'Left Center
    GeneralBottom = 3 'Horizontal Default; Vertical Bottom.   'Left Bottom
    LeftGeneral = 4 'Horizontal Left; Vertical Default.       'Left Center
    LeftTop = 5 'Horizontal Left; Vertical Top.               'Left Top
    LeftCenter = 6 'Horizontal Left; Vertical Center.         'Left Center
    LeftBottom = 7 'Horizontal Left; Vertical Bottom.         'Left Bottom
    CenterGeneral = 8 ' Horizontal Center; Vertical Default.  'Center Center
    CenterTop = 9 'Horizontal Center; Vertical Top.           'Center Top
    CenterCenter = 10 'Horizontal Center; Vertical Center.    'Center Center
    CenterBottom = 11 ' Horizontal Center; Vertical Bottom.   'Center Bottom
    RightGeneral = 12 ' Horizontal Right; Vertical Default.   'Right Center
    RightTop = 13 'Horizontal Right; Vertical Top.            'Right Top
    RightCenter = 14 'Horizontal Right; Vertical Center.      'Right Center
    RightBottom = 15 'Horizontal Right; Vertical Bottom.      'Right Bottom

End Enum

Friend Function Render(ByVal hdc As Long, _
                             Optional ByVal DestX As Long, Optional ByVal DestY As Long, _
                             Optional ByVal DestWidth As Long, Optional ByVal DestHeight As Long, _
                             Optional ByVal srcX As Long, Optional ByVal srcY As Long, _
                             Optional ByVal srcWidth As Long, Optional ByVal srcHeight As Long) As Boolean
                             
   Render = gdipStretchPicture(hdc, DestX, DestY, DestWidth, DestHeight, m_hImage, srcX, srcY, srcWidth, srcHeight)
   
End Function

Public Function gdipStretchPicture(ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal Width As Long, ByVal Height As Long, hImage As Long, ByVal srcX As Long, ByVal srcY As Long, ByVal srcWidth As Long, ByVal srcHeight As Long, Optional ByVal gdipAttributes As Long, Optional ByVal srcUnit As GpUnit = UnitPixel) As Boolean
   
   Dim lR As Long
   lR = -1
   If hImage <> 0 Then
      Dim hGraphics As Long
      lR = GdipCreateFromHDC(hdc, hGraphics)
      lR = GdipDrawImageRectRectI(hGraphics, hImage, x, y, Width, Height, srcX, srcY, srcWidth, srcHeight, srcUnit, gdipAttributes)
      GdipReleaseDC hGraphics, hdc
      GdipDeleteGraphics hGraphics
   End If
   
   If lR = 0 Then gdipStretchPicture = True
   
End Function