delphi – 以实角旋转位图

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曾经读过 this question的时候，我想知道如何在任何程度上旋转位图，而不用自己摆放所有的位。最近 someone else也有明显的困难。

已经有许多问题处理90°间隔的旋转，大多数不合适this one，但是我想要旋转一个真正的角度。最好有可能由于旋转而调整图像尺寸，并为要添加到图像表面的部件设置自定义(透明)背景颜色。那么我假设例程的签名看起来像：

procedure RotateBitmap(Bmp: TBitmap; Angle: Single; AdjustSize: Boolean; 
  BackColor: TColor);

These answers提到以下候选人构建这个例程：SetWorldTransform，PlgBlt，GDI，但我想看到(高效)的实现。

解决方法

tl;dr; Use GDI+

SetWorldTransform

使用WinAPI的SetWorldTransform，您可以转换设备上下文的空间：旋转，剪切，偏移和缩放。这是通过设置XFORM类型的变换矩阵的成员完成的。按照the documentation填写会员。

procedure RotateBitmap(Bmp: TBitmap; Rads: Single; AdjustSize: Boolean;
  BkColor: TColor = clNone);
var
  C: Single;
  S: Single;
  XForm: tagXFORM;
  Tmp: TBitmap;
begin
  C := Cos(Rads);
  S := Sin(Rads);
  XForm.eM11 := C;
  XForm.eM12 := S;
  XForm.eM21 := -S;
  XForm.eM22 := C;
  Tmp := TBitmap.Create;
  try
    Tmp.TransparentColor := Bmp.TransparentColor;
    Tmp.TransparentMode := Bmp.TransparentMode;
    Tmp.Transparent := Bmp.Transparent;
    Tmp.Canvas.Brush.Color := BkColor;
    if AdjustSize then
    begin
      Tmp.Width := Round(Bmp.Width * Abs(C) + Bmp.Height * Abs(S));
      Tmp.Height := Round(Bmp.Width * Abs(S) + Bmp.Height * Abs(C));
      XForm.eDx := (Tmp.Width - Bmp.Width * C + Bmp.Height * S) / 2;
      XForm.eDy := (Tmp.Height - Bmp.Width * S - Bmp.Height * C) / 2;
    end
    else
    begin
      Tmp.Width := Bmp.Width;
      Tmp.Height := Bmp.Height;
      XForm.eDx := (Bmp.Width - Bmp.Width * C + Bmp.Height * S) / 2;
      XForm.eDy := (Bmp.Height - Bmp.Width * S - Bmp.Height * C) / 2;
    end;
    SetGraphicsMode(Tmp.Canvas.Handle,GM_ADVANCED);
    SetWorldTransform(Tmp.Canvas.Handle,XForm);
    BitBlt(Tmp.Canvas.Handle,Tmp.Width,Tmp.Height,Bmp.Canvas.Handle,SRCCOPY);
    Bmp.Assign(Tmp);
  finally
    Tmp.Free;
  end;
end;

PlgBlt

PlgBlt功能执行从源设备上下文中指定的矩形到目标设备上下文中指定的平行四边形的位块传输。通过lpPoint参数映射源图像的角点。

procedure RotateBitmap(Bmp: TBitmap; Rads: Single; AdjustSize: Boolean;
  BkColor: TColor = clNone);
var
  C: Single;
  S: Single;
  Tmp: TBitmap;
  OffsetX: Single;
  OffsetY: Single;
  Points: array[0..2] of TPoint;
begin
  C := Cos(Rads);
  S := Sin(Rads);
  Tmp := TBitmap.Create;
  try
    Tmp.TransparentColor := Bmp.TransparentColor;
    Tmp.TransparentMode := Bmp.TransparentMode;
    Tmp.Transparent := Bmp.Transparent;
    Tmp.Canvas.Brush.Color := BkColor;
    if AdjustSize then
    begin
      Tmp.Width := Round(Bmp.Width * Abs(C) + Bmp.Height * Abs(S));
      Tmp.Height := Round(Bmp.Width * Abs(S) + Bmp.Height * Abs(C));
      OffsetX := (Tmp.Width - Bmp.Width * C + Bmp.Height * S) / 2;
      OffsetY := (Tmp.Height - Bmp.Width * S - Bmp.Height * C) / 2;
    end
    else
    begin
      Tmp.Width := Bmp.Width;
      Tmp.Height := Bmp.Height;
      OffsetX := (Bmp.Width - Bmp.Width * C + Bmp.Height * S) / 2;
      OffsetY := (Bmp.Height - Bmp.Width * S - Bmp.Height * C) / 2;
    end;
    Points[0].X := Round(OffsetX);
    Points[0].Y := Round(OffsetY);
    Points[1].X := Round(OffsetX + Bmp.Width * C);
    Points[1].Y := Round(OffsetY + Bmp.Width * S);
    Points[2].X := Round(OffsetX - Bmp.Height * S);
    Points[2].Y := Round(OffsetY + Bmp.Height * C);
    PlgBlt(Tmp.Canvas.Handle,Points,Bmp.Width,Bmp.Height,0);
    Bmp.Assign(Tmp);
  finally
    Tmp.Free;
  end;
end;

Graphics32

Graphics32是专门用于快速位图处理的库。它需要一些经验来掌握其全部潜力，但the documentation以及所提供的示例应该让您开始。

TBitmap32图像的旋转是通过将许多可用的转换类之一进行转换来完成的。在这里需要TAffineTransformation类。首先，将图像的一半大小移动到左上角，然后旋转，然后将结果移回右下角，可能使用新的图像尺寸。

uses
  GR32,GR32_Transforms;

procedure RotateBitmap(Bmp: TBitmap32; Degs: Integer; AdjustSize: Boolean;
  BkColor: TColor = clNone; Transparent: Boolean = False); overload;
var
  Tmp: TBitmap32;
  Transformation: TAffineTransformation;
begin
  Tmp := TBitmap32.Create;
  Transformation := TAffineTransformation.Create;
  try
    Transformation.BeginUpdate;
    Transformation.SrcRect := FloatRect(0,Bmp.Height);
    Transformation.Translate(-0.5 * Bmp.Width,-0.5 * Bmp.Height);
    Transformation.Rotate(0,-Degs);
    if AdjustSize then
      with Transformation.GetTransformedBounds do
        Tmp.SetSize(Round(Right - Left),Round(Bottom - Top))
    else
      Tmp.SetSize(Bmp.Width,Bmp.Height);
    Transformation.Translate(0.5 * Tmp.Width,0.5 * Tmp.Height);
    Transformation.EndUpdate;
    Tmp.Clear(Color32(BkColor));
    if not Transparent then
      Bmp.DrawMode := dmTransparent;
    Transform(Tmp,Bmp,Transformation);
    Bmp.Assign(Tmp);
    Bmp.OuterColor := Color32(BkColor);
    if Transparent then
      Bmp.DrawMode := dmTransparent;
  finally
    Transformation.Free;
    Tmp.Free;
  end;
end;

procedure RotateBitmap(Bmp: TBitmap; Degs: Integer; AdjustSize: Boolean;
  BkColor: TColor = clNone); overload;
var
  Tmp: TBitmap32;
  Transparent: Boolean;
begin
  Tmp := TBitmap32.Create;
  try
    Transparent := Bmp.Transparent;
    Tmp.Assign(Bmp);
    RotateBitmapGR32(Tmp,Degs,AdjustSize,BkColor,Transparent);
    Bmp.Assign(Tmp);
    if Transparent then
      Bmp.Transparent := True;
  finally
    Tmp.Free;
  end;
end;

GDI

在Windows XP中引入，Microsoft的GDI+ API比默认的GDI API更有效率。对于Delphi 2009及以上版本，库可用@L_404_10@.对于较旧的Delphi版本，库可用from here。

在GDI中，旋转也由变换矩阵完成。绘画的作品有很大的不同。创建TGPGraphics对象并将其附加到其构造函数的设备上下文中。随后，通过API翻译对象的绘制操作，并将其输出到目标上下文。

uses
  GDIPOBJ,GDIPAPI; // < D2009
  GdiPlus;          // >= D2009

procedure RotateBitmap(Bmp: TBitmap; Degs: Integer; AdjustSize: Boolean;
  BkColor: TColor = clNone);
var
  Tmp: TGPBitmap;
  Matrix: TGPMatrix;
  C: Single;
  S: Single;
  NewSize: TSize;
  Graphs: TGPGraphics;
  P: TGPPointF;
begin
  Tmp := TGPBitmap.Create(Bmp.Handle,Bmp.Palette);
  Matrix := TGPMatrix.Create;
  try
    Matrix.RotateAt(Degs,MakePoint(0.5 * Bmp.Width,0.5 * Bmp.Height));
    if AdjustSize then
    begin
      C := Cos(DegToRad(Degs));
      S := Sin(DegToRad(Degs));
      NewSize.cx := Round(Bmp.Width * Abs(C) + Bmp.Height * Abs(S));
      NewSize.cy := Round(Bmp.Width * Abs(S) + Bmp.Height * Abs(C));
      Bmp.Width := NewSize.cx;
      Bmp.Height := NewSize.cy;
    end;
    Graphs := TGPGraphics.Create(Bmp.Canvas.Handle);
    try
      Graphs.Clear(ColorRefToARGB(ColorToRGB(BkColor)));
      Graphs.SetTransform(Matrix);
      Graphs.DrawImage(Tmp,(Cardinal(Bmp.Width) - Tmp.GetWidth) div 2,(Cardinal(Bmp.Height) - Tmp.GetHeight) div 2);
    finally
      Graphs.Free;
    end;
  finally
    Matrix.Free;
    Tmp.Free;
  end;
end;

处理透明度

上面的例程保存了fead位图的透明设置，但需要一个额外的Transparent参数的Graphics32解决方案除外。

性能和图像质量

我写了一个测试应用程序(见下面的完整代码)来调整各种方法的性能，并比较所得到的图像质量。

第一个也是最重要的结论是，GDI使用反锯齿，其他的没有别的，导致最好的图像质量。 (我没有成功尝试通过设置CompositingQuality，InterpolationMode，SmoothingMode和PixelOffsetMode来防止抗锯齿，所以当不使用别名时不要使用GDI。)

此外，GDI解决方案也是迄今为止最快的方法。

unit RotateTestForm;

interface

uses
  Windows,SysUtils,Classes,Graphics,Controls,Forms,Dialogs,ExtCtrls,JPEG,Math,GR32,GR32_Transforms,GDIPOBJ,GDIPAPI {,GdiPlus};

type
  TTestForm = class(TForm)
  private
    FImage: TImage;
    FOpenDialog: TOpenDialog;
    procedure FormPaint(Sender: TObject);
  public
    constructor Create(AOwner: TComponent); override;
  end;

var
  TestForm: TTestForm;

implementation

{$R *.dfm}

procedure RotateBitmapSWT(Bmp: TBitmap; Rads: Single; AdjustSize: Boolean;
  BkColor: TColor = clNone);
var
  C: Single;
  S: Single;
  XForm: TXForm;
  Tmp: TBitmap;
begin
  C := Cos(Rads);
  S := Sin(Rads);
  XForm.eM11 := C;
  XForm.eM12 := S;
  XForm.eM21 := -S;
  XForm.eM22 := C;
  Tmp := TBitmap.Create;
  try
    Tmp.TransparentColor := Bmp.TransparentColor;
    Tmp.TransparentMode := Bmp.TransparentMode;
    Tmp.Transparent := Bmp.Transparent;
    Tmp.Canvas.Brush.Color := BkColor;
    if AdjustSize then
    begin
      Tmp.Width := Round(Bmp.Width * Abs(C) + Bmp.Height * Abs(S));
      Tmp.Height := Round(Bmp.Width * Abs(S) + Bmp.Height * Abs(C));
      XForm.eDx := (Tmp.Width - Bmp.Width * C + Bmp.Height * S) / 2;
      XForm.eDy := (Tmp.Height - Bmp.Width * S - Bmp.Height * C) / 2;
    end
    else
    begin
      Tmp.Width := Bmp.Width;
      Tmp.Height := Bmp.Height;
      XForm.eDx := (Bmp.Width - Bmp.Width * C + Bmp.Height * S) / 2;
      XForm.eDy := (Bmp.Height - Bmp.Width * S - Bmp.Height * C) / 2;
    end;
    SetGraphicsMode(Tmp.Canvas.Handle,SRCCOPY);
    Bmp.Assign(Tmp);
  finally
    Tmp.Free;
  end;
end;

procedure RotateBitmapPLG(Bmp: TBitmap; Rads: Single; AdjustSize: Boolean;
  BkColor: TColor = clNone);
var
  C: Single;
  S: Single;
  Tmp: TBitmap;
  OffsetX: Single;
  OffsetY: Single;
  Points: array[0..2] of TPoint;
begin
  C := Cos(Rads);
  S := Sin(Rads);
  Tmp := TBitmap.Create;
  try
    Tmp.TransparentColor := Bmp.TransparentColor;
    Tmp.TransparentMode := Bmp.TransparentMode;
    Tmp.Transparent := Bmp.Transparent;
    Tmp.Canvas.Brush.Color := BkColor;
    if AdjustSize then
    begin
      Tmp.Width := Round(Bmp.Width * Abs(C) + Bmp.Height * Abs(S));
      Tmp.Height := Round(Bmp.Width * Abs(S) + Bmp.Height * Abs(C));
      OffsetX := (Tmp.Width - Bmp.Width * C + Bmp.Height * S) / 2;
      OffsetY := (Tmp.Height - Bmp.Width * S - Bmp.Height * C) / 2;
    end
    else
    begin
      Tmp.Width := Bmp.Width;
      Tmp.Height := Bmp.Height;
      OffsetX := (Bmp.Width - Bmp.Width * C + Bmp.Height * S) / 2;
      OffsetY := (Bmp.Height - Bmp.Width * S - Bmp.Height * C) / 2;
    end;
    Points[0].X := Round(OffsetX);
    Points[0].Y := Round(OffsetY);
    Points[1].X := Round(OffsetX + Bmp.Width * C);
    Points[1].Y := Round(OffsetY + Bmp.Width * S);
    Points[2].X := Round(OffsetX - Bmp.Height * S);
    Points[2].Y := Round(OffsetY + Bmp.Height * C);
    PlgBlt(Tmp.Canvas.Handle,0);
    Bmp.Assign(Tmp);
  finally
    Tmp.Free;
  end;
end;

procedure RotateBitmapGR32(Bmp: TBitmap32; Degs: Integer; AdjustSize: Boolean;
  BkColor: TColor = clNone; Transparent: Boolean = False); overload;
var
  Tmp: TBitmap32;
  Transformation: TAffineTransformation;
begin
  Tmp := TBitmap32.Create;
  Transformation := TAffineTransformation.Create;
  try
    Transformation.BeginUpdate;
    Transformation.SrcRect := FloatRect(0,Transformation);
    Bmp.Assign(Tmp);
    Bmp.OuterColor := Color32(BkColor);
    if Transparent then
      Bmp.DrawMode := dmTransparent;
  finally
    Transformation.Free;
    Tmp.Free;
  end;
end;

procedure RotateBitmapGR32(Bmp: TBitmap; Degs: Integer; AdjustSize: Boolean;
  BkColor: TColor = clNone); overload;
var
  Tmp: TBitmap32;
  Transparent: Boolean;
begin
  Tmp := TBitmap32.Create;
  try
    Transparent := Bmp.Transparent;
    Tmp.Assign(Bmp);
    RotateBitmapGR32(Tmp,Transparent);
    Bmp.Assign(Tmp);
    if Transparent then
      Bmp.Transparent := True;
  finally
    Tmp.Free;
  end;
end;

procedure RotateBitmapGDIP(Bmp: TBitmap; Degs: Integer; AdjustSize: Boolean;
  BkColor: TColor = clNone);
var
  Tmp: TGPBitmap;
  Matrix: TGPMatrix;
  C: Single;
  S: Single;
  NewSize: TSize;
  Graphs: TGPGraphics;
  P: TGPPointF;
begin
  Tmp := TGPBitmap.Create(Bmp.Handle,(Cardinal(Bmp.Height) - Tmp.GetHeight) div 2);
    finally
      Graphs.Free;
    end;
  finally
    Matrix.Free;
    Tmp.Free;
  end;
end;

{ TTestForm }

constructor TTestForm.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  Font.Name := 'Tahoma';
  Top := 0;
  ClientWidth := 560;
  ClientHeight := 915;
  Show;
  FImage := TImage.Create(Self);
  FOpenDialog := TOpenDialog.Create(Self);
  FOpenDialog.Title := 'Select an small sized image (min. 100 x 100)';
  FOpenDialog.Options := FOpenDialog.Options + [ofFileMustExist];
  FOpenDialog.Filter := 'JPEG|*.JPG|BMP|*.BMP';
  if FOpenDialog.Execute then
  begin
    FImage.Picture.LoadFromFile(FOpenDialog.FileName);
    OnPaint := FormPaint;
    Invalidate;
  end
  else
    Application.Terminate;
end;

procedure TTestForm.FormPaint(Sender: TObject);
var
  Img: TBitmap;
  Bmp: TBitmap;
  Bmp32: TBitmap32;
  BkColor: TColor;
  AdjustSize: Boolean;
  Degs: Integer;
  Rads: Single;
  RotCount: Integer;
  I: Integer;
  Tick: Cardinal;
begin
  Img := TBitmap.Create;
  Bmp := TBitmap.Create;
  Bmp32 := TBitmap32.Create;
  try
    BkColor := clBtnFace;
    Img.Canvas.Brush.Color := BkColor;
    Img.Width := 100;
    Img.Height := 100;
    Img.Canvas.Draw(0,FImage.Picture.Graphic);
    AdjustSize := False;
    Degs := 45;
    Rads := DegToRad(Degs);
    RotCount := 1000;

    Canvas.TextOut(10,10,'Original:');
    Canvas.Draw(10,30,Img);
    Canvas.TextOut(10,140,Format('Size = %d x %d',[Img.Width,Img.Height]));
    Canvas.TextOut(10,160,Format('Angle = %d°',[Degs]));
    Canvas.TextOut(10,250,Format('%d rotations:',[RotCount]));

    Canvas.TextOut(120,'SetWorldTransform:');
    Bmp.Assign(Img);
    RotateBitmapSWT(Bmp,Rads,BkColor);
    Canvas.Draw(120,Bmp);
    if not AdjustSize then
    begin
      Tick := GetTickCount;
      for I := 0 to RotCount - 2 do
        RotateBitmapSWT(Bmp,BkColor);
      Canvas.TextOut(120,Format('%d msec',[GetTickCount - Tick]));
      Canvas.Draw(120,Bmp);
    end;

    Canvas.TextOut(230,'PlgBlt:');
    Bmp.Assign(Img);
    RotateBitmapPLG(Bmp,BkColor);
    Canvas.Draw(230,Bmp);
    if not AdjustSize then
    begin
      Tick := GetTickCount;
      for I := 0 to RotCount - 2 do
        RotateBitmapPLG(Bmp,BkColor);
      Canvas.TextOut(230,[GetTickCount - Tick]));
      Canvas.Draw(230,Bmp);
    end;

    Canvas.TextOut(340,'Graphics32:');
    Bmp.Assign(Img);
    RotateBitmapGR32(Bmp,BkColor);
    Canvas.Draw(340,Bmp);
    if not AdjustSize then
    begin
      Tick := GetTickCount;
      for I := 0 to RotCount - 2 do
        RotateBitmapGR32(Bmp,BkColor);
      Canvas.TextOut(340,[GetTickCount - Tick]));
      Canvas.Draw(340,Bmp);

      // Without in between conversion to TBitmap:
      Bmp32.Assign(Img);
      Tick := GetTickCount;
      for I := 0 to RotCount - 1 do
        RotateBitmapGR32(Bmp32,False);
      Canvas.TextOut(340,270,Format('%d msec (optimized)',[GetTickCount - Tick]));
    end;

    Canvas.TextOut(450,'GDI+ :');
    Bmp.Assign(Img);
    RotateBitmapGDIP(Bmp,BkColor);
    Canvas.Draw(450,Bmp);
    if not AdjustSize then
    begin
      Tick := GetTickCount;
      for I := 0 to RotCount - 2 do
        RotateBitmapGDIP(Bmp,BkColor);
      Canvas.TextOut(450,[GetTickCount - Tick]));
      Canvas.Draw(450,Bmp);
    end;
  finally
    Bmp32.Free;
    Bmp.Free;
    Img.Free;
    OnPaint := nil;
  end;
end;

end.
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