[Lazarus] Slow pointer assignments

[Leonardo M. Ramé]

On 2013-04-18 20:37:06 +0200, Ludo Brands wrote:
> On 04/18/2013 07:53 PM, Leonardo M. Ramé wrote:
> > On 2013-04-18 12:49:07 -0300, Leonardo M. Ramé wrote:
> >> On 2013-04-18 08:48:11 -0700, leledumbo wrote:
> >>> Assign all the RGBA value in one go, that would reduce the inner loop by 4
> >>> times. i.e.:
> >>>
> >>> var 
> >>>   PixelPtr: PLongWord; 
> >>>   PixelRowPtr: PByte; 
> >>> begin 
> >>>   PixelRowPtr := Fbmp.RawImage.Data; 
> >>>   for Y := 0 to Self.Height - 1 do 
> >>>   begin 
> >>>     PixelPtr := PLongWord(PixelRowPtr); 
> >>>     for X := 0 to (Self.Width - 1) div 4 do 
> >>>     begin 
> >>>       PixelPtr^ := (lRed shl 24) or (lGreen shl 16) or (lBlue shl 8) or 255; 
> >>>       Inc(PixelPtr); 
> >>>     end; 
> >>>     Inc(PixelRowPtr, FBmp.RawImage.Description.BytesPerLine); 
> >>>   end;   
> >>> end; 
> >>>
> >>
> >> Great!, I'll try it.
> >>
> > 
> > Well, it's speed improved, but the image is blue... Do you know why?.
> > 
> The Longword is saved low byte first on a LE arch. You need to change
> the order of the colors to
> PixelPtr^ := lRed or (lGreen shl 8) or (lBlue shl 16) or ($ff shl 24);
> Also make sure lRed, etc are bytes. If not use (lRed and $ff) etc.
> 
> Ludo
> 

Yes!, now it works. Thank you and Leledumbo, it works pretty fast.

-- 
Leonardo M. Ramé
http://leonardorame.blogspot.com