[Lazarus] Scanline on certain size images seems to be failing : Access Violation...

[dominique at savagesoftwaresolutions.com]

Please ignore,
  I just realised that ScanLineImage.Free was being called before the
Color_RGBtoColor funcation. Which caused the AV.
Hence why the code works under Delphi, but was AVing with FreePascal.

Dominique.

On Sat, 15 Aug 2009 08:28:53 -0400, <dominique at savagesoftwaresolutions.com>
wrote:
> I have the following 2 functions to determine the transparency colour of
a
> bitmap...
> 
> // Returns the transparent color for the bitmap
> function Bitmap24_TransparentColor(bitmap:TBitmap):TColor;
> var
>   row : PRGBArray;
>   {$IFDEF FPC}
>   ScanLineImage : TLazIntfImage;
>   {$ENDIF}
> begin
>   Result := clBlack;
> 
>   if not IsValidBitmap( bitmap, 'Bitmap24_TransparentColor' ) then
>   begin
>     Exit;
>   end;
> 
>   {$IFDEF FPC}
>   ScanLineImage := bitmap.CreateIntfImage;
>   {$ENDIF}
> 
>   {$IFDEF FPC}
>   row := ScanLineImage.GetDataLineStart( bitmap.Height - 1 );
>   {$ELSE}
>   row := bitmap.ScanLine[ bitmap.Height - 1 ];
>   {$ENDIF}
> 
>   {$IFDEF FPC}
>   ScanLineImage.Free;
>   {$ENDIF}
> 
>   Result := Color_RGBtoColor(row[0]); 
> end;
> 
> // Transforms a RGB color into a standard color
> function Color_RGBToColor(col : TRGB) : TColor;
> begin
>   Result := $10000 *  col.b + $100 * col.g + col.r; // ACCESS VIOLATION
> HERE if Image greater than 640x480
> end;
> 
> I'm getting an Access violation when passing the row[0] to the
RGBtoColor.
> Can anyone see what I might be doing wrong?
> The only thing I noticed is that it seems to fail when I use images
greater
> than 640x480, but I'm willing to concede it may be a bit depth issue.
> Smaller image sizes seem to work fine.
> 
> Would I be right in thinking that row[0] is the bottom right corner of
the
> image?
> 
> Thanks,
> 
> Dominique.
> 
> --
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