如何用 GDI+ 高质量地缩放图片

uses GdiPlus;

procedure TForm1.Button1Click(Sender: TObject);
const
Path1 = 'C:\Temp\Test.png';
Path2 = 'C:\Temp\Test2.png';
var
Img1,Img2: IGPImage;
Graphics: IGPGraphics;
begin
{ 打开原图片 }
Img1 := TGPImage.Create(Path1);

{ 建一个新图片, 假如是缩小一倍 }
Img2 := TGPBitmap.Create(Img1.Width div 2, Img1.Height div 2, PixelFormat32bppARGB);

{ 获取新图片的绘图表面 }
Graphics := TGPGraphics.Create(Img2);

{ 设置缩放质量为最高质量 }
Graphics.InterpolationMode := InterpolationModeHighQualityBicubic;

{ 画过来 }
Graphics.DrawImage(Img1, 0, 0, Img2.Width, Img2.Height, 0, 0, Img1.Width, Img1.Height, UnitPixel);

{ 保存 }
Img2.Save(Path2, TGPImageFormat.Png);
end;