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RGB or RGBA struct from GIF image with GDIPlus

3 posts in this topic

To create a RGB/RGBA struct from a BMP, JPG, PNG or TIF image with GDIPlus you can do something like this:

$hBitmapObj = _GDIPlus_ImageLoadFromFile( $imgFile )

$aPixelFormat = _GDIPlus_ImageGetPixelFormat( $hBitmapObj )
$iPixelFormat = $aPixelFormat[0]
; Inspect the pixel format
; Probably 24 Bpp RGB, 32 Bpp RGB or 32 Bpp ARGB

$bytes = $bytes_per_pixel ; 3 or 4
$width = _GDIPlus_ImageGetWidth( $hBitmapObj )
$height = _GDIPlus_ImageGetHeight( $hBitmapObj )
$size = $width * $height * $bytes

; Lock bitmap for reading
$tBitmapData = _GDIPlus_BitmapLockBits( $hBitmapObj, 0, 0, $width, $height, $GDIP_ILMREAD, $iPixelFormat )

; Create RGB/RGBA struct
$pScan0 = DllStructGetData( $tBitmapData, "Scan0" )
$image = DllStructCreate( "byte[" & $size & "]", $pScan0 )
$pImage = DllStructGetPtr( $image )

How do you create a RGB/RGBA struct from a GIF image?

The problem is that the pixel format for a GIF image is 8 Bpp Indexed. And with this format you can't just use _GDIPlus_BitmapLockBits() to get a RGB/RGBA struct. You have to convert the 8 Bpp Indexed format to e.g. 24 Bpp RGB.

But how do you do that?

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#2 ·  Posted (edited)

Create an empty bitmap using GdipCreateBitmapFromScan0 (see GDIP.au3) in 32 bit format ($GDIP_PXF32RGB) and copy the gif image to the bitmap.

#include <GDIPlus.au3>

$hBitmapObj = _GDIPlus_ImageLoadFromFile("c:\Program Files (x86)\AutoIt3\Examples\GUI\logo4.gif")
$hBitmapObj_new = DllCall($ghGDIPDll, "uint", "GdipCreateBitmapFromScan0", "int", _GDIPlus_ImageGetWidth($hBitmapObj) , "int", _GDIPlus_ImageGetHeight($hBitmapObj) , "int", 0, "int", $GDIP_PXF24RGB, "ptr", 0, "int*", 0)
$hBitmapObj_new = $hBitmapObj_new[6]
$hCtxt = _GDIPlus_ImageGetGraphicsContext($hBitmapObj_new)
_GDIPlus_GraphicsDrawImage($hCtxt, $hBitmapObj, 0, 0)


Func PrintImageFormat($hBitmapObj)
    Local $aPixelFormat = _GDIPlus_ImageGetPixelFormat($hBitmapObj)
    Local $iPixelFormat = $aPixelFormat[0]
    Switch $iPixelFormat
        Case $GDIP_PXF01INDEXED
            ConsoleWrite("$GDIP_PXF01INDEXED" & @LF)
        Case $GDIP_PXF04INDEXED
            ConsoleWrite("$GDIP_PXF04INDEXED" & @LF)
        Case $GDIP_PXF04INDEXED
            ConsoleWrite("$GDIP_PXF04INDEXED" & @LF)
        Case $GDIP_PXF08INDEXED
            ConsoleWrite("$GDIP_PXF08INDEXED" & @LF)
        Case $GDIP_PXF16RGB555
            ConsoleWrite("$GDIP_PXF16RGB555" & @LF)
        Case $GDIP_PXF16RGB565
            ConsoleWrite("$GDIP_PXF16RGB565" & @LF)
        Case $GDIP_PXF16ARGB1555
            ConsoleWrite("$GDIP_PXF16ARGB1555" & @LF)
        Case $GDIP_PXF24RGB
            ConsoleWrite("$GDIP_PXF24RGB" & @LF)
        Case $GDIP_PXF32RGB
            ConsoleWrite("$GDIP_PXF32RGB" & @LF)
        Case $GDIP_PXF32ARGB
            ConsoleWrite("$GDIP_PXF32ARGB" & @LF)
        Case $GDIP_PXF32PARGB
            ConsoleWrite("$GDIP_PXF32PARGB" & @LF)



Edited by UEZ

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