Jpeg压缩的两种方法

一般情况下，采用方法2来操作，压缩效果，可去华军软件园或天空下载站下载“图片伴侣”来体验下。

方法1：

procedure TForm1.Button2Click(Sender: TObject);

var

   JPEGImage: TJPEGImage;

begin

   if SavePictureDialog1.InitialDir =''then

      SavePictureDialog1.InitialDir := ExtractFilePath(OpenPictureDialog1.FileName);

   if trim(LabeledEdit1.Text) <>''then

      SavePictureDialog1.FileName := trim(LabeledEdit1.Text) +'.jpg ';

   if SavePictureDialog1.execute then

   begin

      JPEGImage := TJPEGImage.Create;

      JPEGImage.Assign(image1.Picture.Graphic);

      JPEGImage.CompressionQuality:=25;

      JPEGImage.Compress;

      JPEGImage.SaveToFile(ExtractFilePath(SavePictureDialog1.Filename)+ trim(LabeledEdit1.Text) +'.jpg ');

   end;

end;

方法2：

procedure Tf_NewsPic.BitBtn1Click(Sender: TObject);

var

   i: Integer;

   JI: TJPEGImage;

begin

   if not OpenPictureDialog1.Execute then exit;

   for i :=0 to OpenPictureDialog1.Files.Count -1 do

   begin

      JI := TJPEGImage.Create;

      JI.LoadFromFile(OpenPictureDialog1.Files[i]);

      image4.Picture.Bitmap.Assign(JI);

      JI.Assign(image4.Picture.Bitmap);

      JI.CompressionQuality :=25;

      JI.Compress;

      JI.SaveToFile(zhtier.GetTempDir + ExtractFileName(OpenPictureDialog1.Files[i]));

      Q1.Append;

      TBlobField(Q1.Fieldbyname('图片')).LoadFromFile(OpenPictureDialog1.Files[i]);

      Q1.Post;

      JI.Free;

   end;

   Q1.Last;

end;