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jwilliam

Converting HBITMAP to const unsigned char*

3 posts in this topic

I'm trying to use a function from the leptonica dll. It seems like it should be straightforward, but I'm having no luck with it.

From the documentation:

typedef unsigned char l_uint8

PIX* pixReadMemBmp(const l_uint8 *cdata, size_t size)

Then, in AutoIT, I have:

$leptonicaHandle = DllOpen("path\to\liblept168.dll");

$image = _ScreenCapture_Capture("", $x1, $y1, $x2, $y2);

$tmp = _GDIPlus_BitmapCreateFromHBITMAP($image);
$width = _GDIPlus_ImageGetWidth($tmp);
$height = _GDIPlus_ImageGetHeight($tmp);

$pix = DllCall($leptonicaHandle, "ptr:cdecl", "pixReadMemBmp", "str", $image, "ULONG_PTR", (($width * $height * 24) + 54));
; @error == 0
; $pix[0] == 0x000000

There are no errors when this executes. The call to pixReadMemBmp just returns a bad memory address every time. I read that HBITMAP can be type-cast into uchar * without issue, but I think this may be where my code is off. I have "str" above, but I've tried "str*", "ptr" and "handle" as well.

Also, the last parameter to DllCall is supposed to be the size of the bitmap in bytes (width * height * 24bits/pixel) + 54bytesforheader. I'm not 100% sure this is correct, but I couldn't find any AutoIT functions to get image size from an HBITMAP.

I'd appreciate any thoughts on this. Thanks...

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Actually the documentation says this also.

Read/write to memory [only on linux]

PIX *pixReadMemBmp()

l_int32 pixWriteMemBmp()


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Thanks a lot, BrewMan. I completely missed that. Back to the drawing board...

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