再学GDI+[89]: TGPImage（9） - 图像缩放时的质量（算法）

再学GDI+[89]: TGPImage（9） - 图像缩放时的质量（算法）2012-05-27 博客园万一本例效果图:

代码文件:

unit Unit1;
interface
uses
 Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
 Dialogs, StdCtrls;
type
 TForm1 = class（TForm）
  ListBox1: TListBox;
  procedure FormPaint（Sender: TObject）;
  procedure FormCreate（Sender: TObject）;
  procedure ListBox1Click（Sender: TObject）;
 end;
var
 Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ, GDIPAPI;
var
 n: Single = 0.75; {缩放倍数}
procedure TForm1.FormCreate（Sender: TObject）;
begin
 ListBox1.Align := alRight;
 with ListBox1.Items do
 begin
  add（"InterpolationModeInvalid      "）;
  add（"InterpolationModeDefault      "）;
  add（"InterpolationModeLowQuality     "）;
  add（"InterpolationModeHighQuality    "）;
  add（"InterpolationModeBilinear      "）;
  add（"InterpolationModeBicubic      "）;
  add（"InterpolationModeNearestNeighbor  "）;
  add（"InterpolationModeHighQualityBilinear"）;
  add（"InterpolationModeHighQualityBicubic "）;
 end;
 ListBox1.ItemIndex := 1;
end;
procedure TForm1.FormPaint（Sender: TObject）;
var
 g: TGPGraphics;
 img: TGPImage;
 rt: TGPRectF;
begin
 g := TGPGraphics.Create（Self.Canvas.Handle）;
 img := TGPImage.Create（"C:	emp	est.png"）;
 g.DrawImage（img, 4, 4, img.GetWidth, img.GetHeight）;
 rt := MakeRect（4+img.GetWidth+4, 4, img.GetWidth * n, img.GetHeight * n）;
 g.SetInterpolationMode（ListBox1.ItemIndex - 1）;
 g.DrawImage（img, rt, 0, 0, img.GetWidth, img.GetHeight, UnitPixel）;
 img.Free;
 g.Free;
end;
procedure TForm1.ListBox1Click（Sender: TObject）;
begin
 Repaint;
end;
end.