trouble converting C to ASM

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pinny_woman

Joined: 29 Mar 2008
Posts: 9

pinny_woman 30 Mar 2008, 17:05

Hi,

I've been trying to convert an app written in C to assembly. I've managed well so far with the conversion but have come unstuck with the following:

there's a procedure declared thus:

Code:

HBITMAP CreateMask(HBITMAP hColor, COLORREF crTrans)

which I converted to:

Code:

proc CreateMask, hColor, crTrans
.
.
endp

The problem I'm having is how to pass the params.
The C code is:

Code:

gMask = CreateMask(gImg, RGB(0, 0, 0));

How do I convert the RGB(0,0,0) to pass in asm?

Thanks for your time Wink

30 Mar 2008, 17:05

DJ Mauretto

Joined: 14 Mar 2007
Posts: 464
Location: Rome,Italy

DJ Mauretto 30 Mar 2008, 18:13

Code:

      push    0              ; RGB = 0,0,0    
 push    gImg 
       call    CreateMask


If you Have RGB struct in bytes 

  movzx   eax,byte [Red] 
     shl     eax,16 
     movzx   ebx,byte [Green]  
  shl     ebx,8 
      or      eax,ebx 
    movzx   ecx,byte [Blu] 
     or      eax,ecx 
    push    eax                  ; EAX = 0x00RRGGBB
     push    gImg 
       call    CreateMask

30 Mar 2008, 18:13

itsnobody

Joined: 01 Feb 2008
Posts: 93
Location: Silver Spring, MD

itsnobody 30 Mar 2008, 18:34

Just use 0x00RRGGBB instead of the RGB macro

30 Mar 2008, 18:34

edfed

Joined: 20 Feb 2006
Posts: 4334
Location: Now

edfed 30 Mar 2008, 20:20

Code:

movzx eax,[green]
mov ah,[red]
shl eax,8
mov al,[blue]
push eax
push gimg
call createmask

7 lines instead of 10.

are rgb encoded on bytes or dwords?
cause C convention is to pass params by the stack.
then, you build some equates to access them via the esp or ebp pointer.

30 Mar 2008, 20:20

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