在画布

Question

我需要在另一个位图的画布（主Bitmap）上绘制旋转的位图。但我不知道如何。

我尝试使用TBitMap.Rotate方法旋转位图，然后使用TCanvas.DrawBitmap方法在主BitMap上绘制，但需要花费大量时间（我需要绘制~100个不同角度的相同位图）：

1. 调整BMP大小
2. 旋转BMP
3. 在另一个画布上画画

如何在没有1步和2步的情况下立即绘制旋转的位图？

示例：

var
  Form1: TForm1;
  MainBMP: TBitMap;
  SomeItem: TBitMap;
  buffBMP: TBitMap;

implementation

{$R *.fmx}


procedure TForm1.FormCreate(Sender: TObject);
begin
  MainBMP := TBitMap.Create;
  MainBMP.SetSize(screen.Width, screen.Height);
  SomeItem := TBitMap.Create;
  SomeItem.SetSize(50, 50);
  with SomeItem.Canvas do
  begin
    BeginScene;
    FillRect(rectF(0, 0, 50, 50), 5, 20, allCorners, 1);
    EndScene;
  end;
  buffBMP := TBitMap.Create;
end;

procedure TForm1.Timer1Timer(Sender: TObject);
var
  i: integer;
  rect, sizeRect: TRectF;
begin
  MainBMP.Canvas.BeginScene;
  MainBMP.Canvas.Clear($FF777777);
  for i := 1 to 10000 do
  begin
    buffBMP.Assign(SomeItem);
    buffBMP.Rotate(random(360));
    sizeRect := rectF(0, 0, buffBMP.Width, buffBMP.Height);
    rect := sizeRect;
    rect.Offset(random(1200), random(600));
    MainBMP.Canvas.DrawBitmap(buffBMP, sizeRect, rect, 1);
  end;
  MainBMP.Canvas.EndScene;
  Form1.Canvas.BeginScene;
  Form1.Canvas.DrawBitmap(MainBMP, ClientRect, ClientRect, 1);
  Form1.Canvas.EndScene;
end;

不

buffBMP.Rotate(random(360));

需要16-32毫秒。使用此方法：~8500 ms

我正在寻找像

这样的方法

TCanvas.DrawBitmap(const ABitmap: TBitmap; const SrcRect, DstRect: TRectF; const AOpacity: Single; const HighSpeed: Boolean);

但添加了角度：单参数

机器人。 FMX。

感谢。

Answer 1

You should use a transformation Matrix instead of the Rotate method on the bitmap.

Such could look like:

procedure TForm1.Timer1Timer(Sender: TObject);
var
  I: Integer;
  R: TRectF;
  SaveMatrix: TMatrix;
  Matrix: TMatrix;
begin
  MainBMP.Canvas.BeginScene;
  MainBMP.Canvas.Clear($FF777777);
  SaveMatrix := MainBmp.Canvas.Matrix;
  for I := 1 to 1000 do
  begin
    BuffBMP.Assign(SomeItem);
    R := RectF(0, 0, BuffBMP.Width, BuffBMP.Height);
    Matrix := CreateRotationMatrix(DegToRad(Random(360)));
    Matrix.m31 := Random(1200);
    Matrix.m32 := Random(600);
    MainBMP.Canvas.SetMatrix(Matrix);
    MainBMP.Canvas.DrawBitmap(buffBMP, R, R, 1, True);
  end;
  MainBMP.Canvas.SetMatrix(SaveMatrix);
  MainBMP.Canvas.EndScene;
  Canvas.BeginScene;
  Canvas.DrawBitmap(MainBMP, ClientRect, ClientRect, 1);
  Canvas.EndScene;
end;