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.

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.

I have the following 2 functions to determine the transparency colour of

a

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

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.

Note:
The ScanLine differences have nothing to do with FPC, but with the LCL. You can use:

{$IFDEF LCL}

Mattias

When trying to convert Bitmap manipulation stuff using Scanline from Delphi to Freepascal / Lazarus Opbitmap might help you. http://www.theo.ch/lazarus/opbitmap64.zip

If you are not on 32 bit intel install the opbitmapforlazcompat.lpk package.

The demos should get you going.

I don't know if this is what you need.

I didn't know there was an LCL define hence why I used FPC. I'll use that from now on.

Thanks for the heads up.

Dominique.

Thanks for the link Theo. The stuff I have works on Win32 with Delphi, its just getting it all working with FPC and LCL on Mac OS X that I'm trying to do.

Dominique