如何直接在FMX2中访问TBitmap像素（TBitmap.ScanLine替换）？

Question

The FMX.Types.TBitmap class has the ScanLine property in FMX (FireMonkey), but it seems this property was removed, and is missing in FMX2 (FireMonkey FM2).

Is there any workaround ? How do we supposed to access TBitmap content directly in FMX2 ?

Answer 1

For direct access you are expect to use the Map method. The documentation includes a number of examples, such as FMX.AlphaColorToScanline :

function TForm1.TestAlphaColorToScanline(ABitmap: TBitmap;
  start, count: integer): TBitmap;
var
  bitdata1, bitdata2: TBitmapData;
begin
  Result := TBitmap.Create(Round(ABitmap.Width), Round(count));
  if (ABitmap.Map(TMapAccess.maRead, bitdata1) and
    Result.Map(TMapAccess.maWrite, bitdata2)) then
  begin
    try
      AlphaColorToScanline(@PAlphaColorArray(bitdata1.Data)
        [start * (bitdata1.Pitch div GetPixelFormatBytes(ABitmap.PixelFormat))],
        bitdata2.Data, Round(Result.Height * Result.Width),
        ABitmap.PixelFormat);
    finally
      ABitmap.Unmap(bitdata1);
      Result.Unmap(bitdata2);
    end;
  end;
end;

Answer 2

Here is an example for C++Builder (the current docs are completely missing such):

int X, Y;
TBitmapData bm;

// get bitmap data access !
if ( Image1->Bitmap->Map(TMapAccess::maReadWrite, bm) )
{
    unsigned int* data = (unsigned int*)bm.Data;

    // i.e. clear data with alpha color
    memset(data, 0,
    Image1->Width * Image1->Height * sizeof(unsigned int));

    // test direct pixel access here
    for (X = 20; X <= 200; X++)
    {
        for (Y = 10; Y <= 100; Y++)
        {
            //MyBitmap->Pixels[X][Y] = claLime;  // does not work anymore !
            bm.SetPixel(X, Y, claLime);
        }
    }

    // now write back the result !
    Image1->Bitmap->Unmap(bm);
}
else
{
    MessageDlg("Could not map the image data for direct access.",
    TMsgDlgType::mtWarning, TMsgDlgButtons() << TMsgDlgBtn::mbOK, 0);
}