[Lazarus] Slow pointer assignments

[Ludo Brands]

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