Delphi中图像混合透明的函数AlphaBlend的使用

 下面的测试是把一张图片显示在窗体, 并可以调整透明度.unit Unit1;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ComCtrls;type TForm1 = class(TForm) TrackBar1: TTrackBar; procedure FormCreate(Sender: TObject); procedure FormDestroy(Sender: TObject); procedure TrackBar1Change(Sender: TObject); procedure FormPaint(Sender: TObject); end;var Form1: TForm1;implementation{$R *.dfm}var bit: TBitmap;procedure TForm1.FormCreate(Sender: TObject);begin bit := TBitmap.Create; bit.LoadFromFile('c:/temp/Test.bmp'); TrackBar1.Min := 0; TrackBar1.Max := 255; TrackBar1.Position := 128; DoubleBuffered := True;end;procedure TForm1.FormDestroy(Sender: TObject);begin bit.Free;end;procedure TForm1.FormPaint(Sender: TObject);var BlendFunc: TBlendFunction;begin BlendFunc.BlendOp := AC_SRC_OVER; BlendFunc.BlendFlags := 0; BlendFunc.SourceConstantAlpha := TrackBar1.Position; if bit.PixelFormat = pf32bit then BlendFunc.AlphaFormat := AC_SRC_ALPHA else BlendFunc.AlphaFormat := 0; Windows.AlphaBlend(Canvas.Handle, {目标 DC} 30, 10, bit.Width, bit.Height, {目标位置与大小} bit.Canvas.Handle, {源 DC} 0, 0, bit.Width, bit.Height, {源位置与大小} BlendFunc {透明相关的结构} );end;procedure TForm1.TrackBar1Change(Sender: TObject);begin Repaint;end;end.