//

// ------------------------------------------------------------------------------------

//

// uPicPress.pas -- jpg图片压缩：

//

//                            本单元由 佛也没辙q：340066709 亲情奉献

//                                 本单元只在高版本测试通过

// ------------------------------------------------------------------------------------

//

unit uPicPress;

interface

uses

  Winapi.Windows, System.SysUtils, Vcl.Graphics, Vcl.ExtCtrls, Vcl.Imaging.jpeg;

function GetNewSize(OldWidth, OldHeight: integer; NewWidth, NewHeight: integer; var RetWidth, RetHeight: integer):Boolean;

function CompressImageFile(FileName: string;  Width, Height: integer; PressQuality:Integer= 90; outFileName: string=''): Boolean;

implementation

// 计算图片大小比例；

function GetNewSize(OldWidth, OldHeight: integer; NewWidth, NewHeight: integer; var RetWidth, RetHeight: integer):Boolean;

var

   H:Boolean;

begin

   Result := False;

   if (NewHeight < OldHeight) or (NewWidth < OldWidth) then

   begin

      H := NewHeight < OldHeight;

      if H then

      begin //按比例缩小,按高度来算高度的

         RetHeight := NewHeight;

         RetWidth := Round(OldWidth *  (NewHeight/OldHeight));

      end

      else

      begin //按比例缩小,按宽度来算宽度的

         RetWidth := NewWidth;

         RetHeight := Round(OldHeight * (NewWidth/OldWidth));

      end;

      Result:=True;

   end;

end;

// 压缩图片；

function CompressImageFile(FileName: string;  Width, Height: integer; PressQuality:Integer= 100; outFileName: string=''): Boolean;

var

   bmp: TBitmap;

   jpg: TJpegImage;

   i: Integer;

begin

  Result := False;

  try

    bmp := TBitmap.Create;

    jpg := TJPEGImage.Create;

    if pos(UpperCase('.jpg'), UpperCase(FileName)) <> 0 then //jpg其它格式

    begin

      if Trim(outFileName) = '' then

        outFileName := 'd:/tmp.jpg';

      jpg.LoadFromFile(FileName);

      if GetNewSize(jpg.Width, jpg.height, Width, Height, Width, Height) then

      begin

        bmp.height := Height;

        bmp.Width := Width;

        bmp.Canvas.StretchDraw(bmp.Canvas.ClipRect, jpg);

        jpg.Assign(bmp);

        jpg.CompressionQuality := PressQuality;

        jpg.Compress;

        jpg.SaveToFile(outFileName);

        Result := True;

      end;

    end;

  finally

    FreeAndNil(bmp);

    FreeAndNil(jpg);

  end;

end;

end.