delphi - 如何设置 FMX.Canvas 上光标下像素的颜色？

Question

对于 vcl，我使用了这个:

procedure MovingDots(X, Y: Integer; ACanvas: TCanvas); stdcall;
begin
{$R-}
  Inc(ALooper);
  ACounter := ACounter shl 1; // Shift the bit left one
  if ACounter = 0 then
    ACounter := 1; // If it shifts off left, reset it
  if (ACounter and 224) > 0 then // Are any of the left 3 bits set?
    // FMX.Canvas does not have Pixels
    ACanvas.Pixels[X, Y] := ASelectionColor1 // Erase the pixel
  else
    ACanvas.Pixels[X, Y] := ASelectionColor2; // Draw the pixel
{$R+}
end;

如何从 FMX Canvas 设置 X、Y 处的颜色？

Answer 1

根据这个example ，这应该有效:

var
  vBitMapData : TBitmapData;
  ASelectionColor : TAlphaColor;
...
// Define ASelectionColor somewhere
// Get write access to the bitmap
if ACanvas.Bitmap.Map (TMapAccess.maWrite, vBitMapData) then
begin
  try
    vBitmapData.SetPixel (x, y, ASelectionColor); // set the pixel color at x, y
  finally
    ACanvas.Bitmap.Unmap(vBitMapData);
  end;
end; 

请注意，锁定/解锁位图的映射策略是在 FM2(即 Delphi-XE3)中引入的。