1.JPEG 转换为BMP函数

procedure Jpg2Bmp(const source,dest:string);
var
  MyJpeg: TJpegImage;
  bmp: Tbitmap;
begin
bmp:=tbitmap.Create;
MyJpeg:= TJpegImage.Create;
try
  myjpeg.LoadFromFile(source);
  bmp.Assign(myjpeg);
  bmp.SaveToFile(dest);
finally
  bmp.free;
  myjpeg.Free;
end;
end;

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2.Bmp转换为JPEG文件格式函数
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procedure Bmp2Jpg(const source,dest:string;const scale:byte);
var
  MyJpeg: TJpegImage;
  Image1: TImage;
begin
Image1:= TImage.Create(application);
MyJpeg:= TJpegImage.Create;
try
  Image1.Picture.Bitmap.LoadFromFile(source);
  MyJpeg.Assign(Image1.Picture.Bitmap);
  MyJpeg.CompressionQuality:=scale;
  MyJpeg.Compress;
  MyJpeg.SaveToFile(dest);
finally
  image1.free;
  myjpeg.Free;
end;