delphi – 如何使用纯GDI对画布区域进行颜色混合(按指定的alpha值着色)？

我想使用纯 Windows GDI(不使用GDI,DirectX或类似,没有OpenGL,没有汇编程序或第三方库)对画布区域进行颜色混合(使用指定的alpha值着色).

我已经创建了以下函数,我想知道是否有更高效或更简单的方法来执行此操作：

procedure ColorBlend(const ACanvas: HDc; const ARect: TRect;
  const ABlendColor: TColor; const ABlendValue: Integer);
var
  DC: HDc;
  Brush: HBRUSH;
  Bitmap: HBITMAP;
  BlendFunction: TBlendFunction;
begin
  DC := CreateCompatibleDC(ACanvas);
  Bitmap := CreateCompatibleBitmap(ACanvas,ARect.Right - ARect.Left,ARect.bottom - ARect.Top);
  Brush := CreateSolidBrush(ColorToRGB(ABlendColor));
  try
    SELEctObject(DC,Bitmap);
    Windows.FillRect(DC,Rect(0,ARect.bottom - ARect.Top),Brush);
    BlendFunction.blendop := AC_SRC_OVER;
    BlendFunction.blendFlags := 0;
    BlendFunction.AlphaFormat := 0;
    BlendFunction.sourceConstantAlpha := ABlendValue;
    Windows.AlphaBlend(ACanvas,ARect.Left,ARect.Top,ARect.bottom - ARect.Top,DC,BlendFunction);
  finally
    deleteObject(Brush);
    deleteObject(Bitmap);
    deleteDC(DC);
  end;
end;

有关此功能应该做什么的概念,请参阅以下内容(区分:-)图像：

并且代码可以通过上面显示的方式将this image呈现到表单的左上方：

uses
  PNGImage;

procedure TForm1.button1Click(Sender: TObject);
var
  Image: TPNGImage;
begin
  Image := TPNGImage.Create;
  try
    Image.LoadFromFile('d:\6G3Eg.png');
    ColorBlend(Image.Canvas.Handle,Image.Canvas.ClipRect,$0000FF80,175);
    Canvas.Draw(0,ImagE);
  finally
    Image.Free;
  end;
end;

使用纯GDI或Delphi VCL有更有效的方法吗？

Canvas.Draw(Arect.Left,ABitmap,AAlphaBlendvalue);

procedure ColorBlend(const ACanvas: TCanvas; const ARect: TRect;
  const ABlendColor: TColor; const ABlendValue: Integer);
var
  bmp: TBitmap;
begin
  bmp := TBitmap.Create;
  try
    bmp.Canvas.brush.Color := ABlendColor;
    bmp.Width := ARect.Right - ARect.Left;
    bmp.Height := ARect.bottom - ARect.Top;
    bmp.Canvas.FillRect(Rect(0,bmp.Width,bmp.Height));
    ACanvas.Draw(ARect.Left,bmp,ABlendvalue);
  finally
    bmp.Free;
  end;
end;

procedure TForm1.button1Click(Sender: TObject);
var
  Image: TPNGImage;
begin
  Image := TPNGImage.Create;
  try
    Image.LoadFromFile('d:\6G3Eg.png');
    ColorBlend(Image.Canvas,ImagE);
    // then for fun do it to the Form itself
    ColorBlend(Canvas,ClientRect,clYellow,15);
  finally
    Image.Free;
  end;
end;