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RagsRevenge

Set pixels per inch using GDI+

3 posts in this topic

Hi,

I have some code which resizes an image so the longest side is a prespecified value. Resizing is done which retains the aspect ratio of the image.

Is there any function of GDI+ which allows me to specify the ppi or dpi of the image? Currently, all of my resized images are set to 96dpi, but I'd also like to be able to set them to 72dpi.

Thanks for any help, and here is some of the core code

$hWnd = _WinAPI_GetDesktopWindow()
        $hDC = _WinAPI_GetDC($hWnd)
        $hBMP = _WinAPI_CreateCompatibleBitmap($hDC, $iW, $iH)
        _WinAPI_ReleaseDC($hWnd, $hDC)
        $hImage1 = _GDIPlus_BitmapCreateFromHBITMAP($hBMP)
        $hGraphic = _GDIPlus_ImageGetGraphicsContext($hImage1)
        _GDIPlus_GraphicsDrawImageRect($hGraphic, $hImage2, 0, 0, $iW, $iH)
        $CLSID = _GDIPlus_EncodersGetCLSID($Ext)
        _GDIPlus_ImageSaveToFileEx($hImage1, $sOutImage, $CLSID)
        _GDIPlus_ImageDispose($hImage1)
        _GDIPlus_ImageDispose($hImage2)
        _GDIPlus_GraphicsDispose($hGraphic)
        _WinAPI_DeleteObject($hBMP)
        _GDIPlus_Shutdown()

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Maybe this could help you (taken from GDIP.au3):

; #FUNCTION# ====================================================================================================================
; Name...........: _GDIPlus_BitmapSetResolution
; Description ...: Sets the resolution of this Bitmap object
; Syntax.........: _GDIPlus_BitmapSetResolution($hBitmap, $nDpiX, $nDpiY)
; Parameters ....: $hBitmap - Pointer to the Bitmap object
;   $nDpiX  - Value that specifies the horizontal resolution in dots per inch.
;   $nDpiX  - Value that specifies the vertical resolution in dots per inch.
; Return values .: Success  - True
;   Failure     - False and either:
;   |@error and @extended are set if DllCall failed
;   |$GDIP_STATUS contains a non zero value specifying the error code
; Remarks .......: None
; Related .......:
; Link ..........; @@MsdnLink@@ GdipBitmapSetResolution
; Example .......; Yes
; ===============================================================================================================================
Func _GDIPlus_BitmapSetResolution($hBitmap, $nDpiX, $nDpiY)
    Local $aResult = DllCall($ghGDIPDll, "uint", "GdipBitmapSetResolution", "hwnd", $hBitmap, "float", $nDpiX, "float", $nDpiY)

    If @error Then Return SetError(@error, @extended, False)
    $GDIP_STATUS = $aResult[0]
    Return $aResult[0] = 0
EndFunc ;==>_GDIPlus_BitmapSetResolution

Br,

UEZ


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Maybe this could help you (taken from GDIP.au3):

; #FUNCTION# ====================================================================================================================
; Name...........: _GDIPlus_BitmapSetResolution

Br,

UEZ

$hWnd = _WinAPI_GetDesktopWindow()
        $hDC = _WinAPI_GetDC($hWnd)
        $hBMP = _WinAPI_CreateCompatibleBitmap($hDC, $iW, $iH)
        _WinAPI_ReleaseDC($hWnd, $hDC)
        $hImage1 = _GDIPlus_BitmapCreateFromHBITMAP($hBMP)
        
        _GDIPlus_BitmapSetResolution($hImage1, 72, 72)
        
        $hGraphic = _GDIPlus_ImageGetGraphicsContext($hImage1)
        _GDIPlus_GraphicsDrawImageRect($hGraphic, $hImage2, 0, 0, $iW, $iH)
        $CLSID = _GDIPlus_EncodersGetCLSID($Ext)
        _GDIPlus_ImageSaveToFileEx($hImage1, $sOutImage, $CLSID)
        _GDIPlus_ImageDispose($hImage1)
        _GDIPlus_ImageDispose($hImage2)
        _GDIPlus_GraphicsDispose($hGraphic)
        _WinAPI_DeleteObject($hBMP)
        _GDIPlus_Shutdown()

That works a charm UEZ, thanks. I simply needed to add 1 further function call. I didn't know about gdip.au3, so thanks to Authenticity too.

Mfg,

D

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