再學 GDI+[99]: TGPImage(19) - 把圖像轉存為其他格式

本例效果圖:

　　代碼文件: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+ 全部可以讀取的圖片格式|*.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 := '打開';
　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('先要打開文件');
　　Exit;
　end;
　{一次性保存為 5 種可能的格式}
　for i := 0 to 4 do
　begin
　　GetEncoderClsid(ArrEncodeName[i], ImgGUID); {先獲取格式編碼}
　　img.Save(ChangeFileExt(FileName, ArrExt[i]), ImgGUID);
　end;
　Beep;
end;
end.窗體文件:object Form1: TForm1
　Left = 0
　Top = 0
　Caption = 'Form1'
　ClIEntHeight = 207
　ClIEntWidth = 299
　Color = clBtnFace
　Font.Charset = DEFAULT_CHARSET
　Font.Color = clWindowText
　Font.Height = -11
　Font.Name = 'Tahoma'
　Font.Style = []
　OldCreateOrder = False
　Position = poDesktopCenter
　OnCreate = FormCreate
　OnDestroy = FormDestroy
　OnPaint = FormPaint
　PixelsPerInch = 96
　TextHeight = 13
　object Button1: TButton
　　Left = 135
　　Top = 174
　　Width = 75
　　Height = 25
　　Caption = 'Button1'
　　TabOrder = 0
　　OnClick = Button1Click
　end
　object Button2: TButton
　　Left = 216
　　Top = 174
　　Width = 75
　　Height = 25
　　Caption = 'Button2'
　　TabOrder = 1
　　OnClick = Button2Click
　end
　object OpenDialog1: TOpenDialog
　　Left = 152
　　Top = 104
　end
end