再学GDI+[99]: TGPImage（19） - 把图像转存为其他格式

再学GDI+[99]: TGPImage（19） - 把图像转存为其他格式2012-06-02 cnblogs 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, ExtCtrls;
type
 TForm1 = class（TForm）
  OpenDialog1: TOpenDialog;
  Button1: TButton;
  Button2: TButton;
  procedure FormCreate（Sender: TObject）;
  procedure FormDestroy（Sender: TObject）;
  procedure FormPaint（Sender: TObject）;
  procedure Button1Click（Sender: TObject）;
  procedure Button2Click（Sender: TObject）;
 end;
var
 Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ, GDIPAPI, GDIPUTIL;
const
 OpenFileFilter =
  "GDI+ 全部可以读取的图片格式|*.png;*.jpg;*.gif;*.bmp;*.tif;*.emf;*.wmf;*.ico" +
  "|*.png|*.png" +
  "|*.jpg|*.jpg" +
  "|*.gif|*.gif" +
  "|*.bmp|*.bmp" +
  "|*.tif|*.tif" +
  "|*.emf|*.emf" +
  "|*.wmf|*.wmf" +
  "|*.ico|*.ico";
 ArrExt: array[0..4] of String = （".png", ".jpg", ".gif", ".bmp", ".tif"）;
 ArrEncodeName: array[0..4] of String =
  （"image/png", "image/jpeg", "image/gif", "image/bmp", "image/tiff"）;
var
 FileName: string;
 img: TGPImage;
procedure TForm1.FormCreate（Sender: TObject）;
begin
 img := TGPImage.Create;
 Button1.Caption := "打开";
 Button2.Caption := "保存";
end;
procedure TForm1.FormDestroy（Sender: TObject）;
begin
 img.Free;
end;
procedure TForm1.FormPaint（Sender: TObject）;
var
 g: TGPGraphics;
begin
 if FileName <> "" then
 begin
  g := TGPGraphics.Create（Canvas.Handle）;
  g.DrawImage（img, 10, 10, img.GetWidth, img.GetHeight）;
  g.Free;
 end;
end;
procedure TForm1.Button1Click（Sender: TObject）;
begin
 OpenDialog1.Filter := OpenFileFilter;
 if OpenDialog1.Execute then
 begin
  FileName := OpenDialog1.FileName;
  img.Free;
  img := TGPImage.Create（FileName）;
  Repaint;
 end;
end;
procedure TForm1.Button2Click（Sender: TObject）;
var
 ImgGUID: TGUID;
 i: Integer;
begin
 if FileName = "" then
 begin
  ShowMessage（"先要打开文件"）;
  Exit;
 end;
 {一次性保存为 5 种可能的格式}
 for i := 0 to 4 do
 begin
  GetEncoderClsid（ArrEncodeName[i], ImgGUID）; {先获取格式编码}
  img.Save（ChangeFileExt（FileName, ArrExt[i]）, ImgGUID）;
 end;
 Beep;
end;
end.