TPaintBox 使用 SetWorldTransform 旋转图像

Question

我正在将图像加载到 TPaintBox，然后尝试使用 SetWorldTransform as suggested in this answer:

旋转它

图片通过 TPaintBox.Invalidate -> TPaintBox.OnPaint 加载正常。
但是当我点击测试按钮 BtnRotateWorldTransform 时，我看到图像闪烁但没有旋转。

procedure TFrmRotateImage.FormCreate(Sender: TObject);
begin
  FWICImage := TWICImage.Create; 
end;

procedure TFrmRotateImage.BtnLoadPaintBoxClick(Sender: TObject);
begin
   if DlgOpen.Execute then  // PNG or JPG file
   begin
      try
         FWICImage.LoadFromFile(DlgOpen.FileName);
         FBoxLoaded := true;
         PaintBox.Invalidate;
      finally
      end;
   end;
end;

procedure TFrmRotateImage.PaintBoxPaint(Sender: TObject);  // OnPaint handler
begin
   if not FBoxLoaded then Exit;
   PaintBox.Canvas.Draw(0,0,FWICImage);
end;

procedure TFrmRotateImage.BtnRotateWorldTransformClick(Sender: TObject);  // Test button
var
   lRect: TRect;
begin
   lRect.Top    := PaintBox.Top;
   lRect.Left   := PaintBox.Left;
   lRect.Width  := PaintBox.Width;
   lRect.Height := PaintBox.Height;
   StretchDrawRotated(PaintBox.Canvas,lRect,90,lRect.CenterPoint,FWICImage);
   PaintBox.Invalidate;
end;

和

procedure XForm_SetRotation(out AXForm: TXForm; AAngle: Extended; ACenter: TPoint);
var
  SinA, CosA: Extended;
begin
  SinCos(AAngle, SinA, CosA);
  AXForm.eM11 := CosA;
  AXForm.eM12 := SinA;
  AXForm.eM21 := -SinA;
  AXForm.eM22 := CosA;
  AXForm.eDx := (ACenter.X - (CosA * ACenter.X)) + ((SinA * ACenter.Y));
  AXForm.eDy := (ACenter.Y - (SinA * ACenter.X)) - ((CosA * ACenter.Y));
end;

procedure StretchDrawRotated(ACanvas: TCanvas; const ARect: TRect; AAngle: Extended; ACenter: TPoint; AGraphic: TGraphic);
var
  XForm, XFormOld: TXForm;
  GMode: Integer;
begin
  GMode := SetGraphicsMode(ACanvas.Handle, GM_ADVANCED);
  try
    if GetWorldTransform(ACanvas.Handle, XFormOld) then
      try
        XForm_SetRotation(XForm, AAngle, ACenter);
        SetWorldTransform(ACanvas.Handle, XForm);
        ACanvas.StretchDraw(ARect, AGraphic);
      finally
        SetWorldTransform(ACanvas.Handle, XFormOld);
      end;
  finally
    SetGraphicsMode(ACanvas.Handle, GMode);
  end;
end;

我忘记了什么？

Answer 1

我写了一个完整的例子。在此示例中，我展示了如何旋转、平移、缩放图像以及组合这些变换。

为此，我编写了 3 个函数来轻松准备旋转、缩放和平移。

在 PaintBox1Paint 事件处理程序中，我采用固定值进行旋转、缩放和平移。当然，在正常的应用程序中，它来自其他地方（例如 UI）。转换计算应在 PaintBox1Paint 过程之外，并在每次参数变化时完成。然后应调用 Invalidate，以便使用新的计算转换重新绘制它。

procedure TForm4.FormCreate(Sender: TObject);
begin
    FWICImage := TWICImage.Create;
end;

procedure TForm4.FormDestroy(Sender: TObject);
begin
    FreeAndNil(FWICImage);
end;

procedure TForm4.LoadImageButtonClick(Sender: TObject);
begin
    FWICImage.LoadFromFile('C:\Users\fpiette\Pictures\Delphi25 ICS.jpg');
    FBoxLoaded := TRUE;
    PaintBox1.Invalidate;
end;

function XForm_SetRotation(
    AAngle     : Single;
    ACenter    : TPoint) : TXForm;
var
    SinA, CosA: Extended;
begin
    SinCos(AAngle, SinA, CosA);
    Result.eM11 := CosA;
    Result.eM12 := SinA;
    Result.eM21 := -SinA;
    Result.eM22 := CosA;
    Result.eDx := (ACenter.X - (CosA * ACenter.X)) + ((SinA * ACenter.Y));
    Result.eDy := (ACenter.Y - (SinA * ACenter.X)) - ((CosA * ACenter.Y));
end;

function XForm_SetScale(
    const AZoomX : Single;
    const AZoomY : Single;
    const center: TPoint) : TXForm;
begin
    Result.eM11 := AZoomX;
    Result.eM12 := 0.0;
    Result.eM21 := 0.0;
    Result.eM22 := AZoomY;
    Result.eDx  := center.x - AZoomX * center.x;
    Result.eDy  := center.y - AZoomY * center.y;
end;

function XForm_SetTranslate(
    const ADistX : Integer;
    const ADistY : Integer) : TXForm;
begin
    Result.eM11 := 1.0;
    Result.eM12 := 0.0;
    Result.eM21 := 0.0;
    Result.eM22 := 1.0;
    Result.eDx  := ADistX;
    Result.eDy  := ADistY;
end;

procedure TForm4.PaintBox1Paint(Sender: TObject);
var
    XFormScale  : TXForm;
    XFormRot    : TXForm;
    XFormXLat   : TXForm;
    XForm       : TXForm;
    XFormOld    : TXForm;
    GMode       : Integer;
    AZoomFactor : Single;
    AAngle      : Single;
    ADistX      : Integer;
    ADistY      : Integer;
    ACanvas     : TCanvas;
begin
    if not FBoxLoaded then
        Exit;

    AZoomFactor := 0.25;
    AAngle      := 30.0;
    ADistX      := 100;
    ADistY      := 200;
    ACanvas     := PaintBox1.Canvas;

    GMode := SetGraphicsMode(ACanvas.Handle, GM_ADVANCED);
    try
        if GetWorldTransform(ACanvas.Handle, XFormOld) then begin
            try
                XFormRot   := XForm_SetRotation(
                                  AAngle,
                                  Point(FWICImage.Width div 2,
                                        FWICImage.Height div 2));
                XFormScale := XForm_SetScale(
                                  AZoomFactor, AZoomFactor, Point(0, 0));
                XFormXLat  := XForm_SetTranslate(ADistX, ADistY);
                CombineTransform(XForm, XFormRot, XFormScale);
                CombineTransform(XForm, XForm,    XFormXLat);
                SetWorldTransform(ACanvas.Handle, XForm);
                ACanvas.Draw(0, 0, FWICImage);
            finally
                SetWorldTransform(ACanvas.Handle, XFormOld);
            end;
        end;
    finally
        SetGraphicsMode(ACanvas.Handle, GMode);
    end;
end;

TPaintBox 使用 SetWorldTransform 旋转图像

TPaintBox rotate image with SetWorldTransform

delphi

vcl

image

rotation

delphi-10.4-sydney