Jpeg到Bmp转换花费的时间不合理 [英] Jpeg to Bmp conversion takes unreasonable amount of time
问题描述
我有此功能需要4.2秒才能将jpg转换为bmp。
为什么要花这么长时间？我可以提高速度吗？
IrfanView可以在那一小段时间内加载并转换文件。
我认为大部分时间都用在JPG.LoadFromFile中。但是当我测量时间时，我惊讶地发现它花了大部分时间在BMP.Assing（JPG）上。
功能ConvertJPG2BMP（CONST FileName：string）：TBitmap;
VAR JPG：TJpegImage；
开始
结果：= NIL;
JPG：= TJpegImage.Create;
尝试
JPG.LoadFromFile（FileName）;
如果（JPG.Width> 0）AND（JPG.Width< 32768）
AND（JPG.Height> 0）AND（JPG.Height< 32768）然后
开始
结果：= TBitmap.Create;
TRY
Result.HandleType：= bmDIB;
// Fuji_FinePix_F550.JPG [3200x1800] [1.44MB]
Result.Assign（JPG）; <-4秒！
除
FreeAndNil（Result）;
END；
结尾；
最终
FreeAndNil（JPG）;
结尾；
结尾；
由于我只想测试稍旧一些的功能，这是一个很好的机会。
function ConvertJPG2BMP（CONST FileName ：string）：TBitmap;
VAR
JPG：TJpegImage；
开始
结果：= NIL;
JPG：= TJpegImage.Create;
尝试
JPG.LoadFromFile（FileName）;
如果（JPG.Width> 0）AND（JPG.Width< 32768）
AND（JPG.Height> 0）AND（JPG.Height< 32768）AND
开始
结果：= TBitmap.Create;
尝试
Result.PixelFormat：= pf24bit;
Result.Width：= JPG.Width;
Result.Height：= JPG.Height;
Result.HandleType：= bmDIB;
// 2018-10-17 14.04.23.jpg [2560x1920] [1.66MB]
Result.Assign（JPG）;
Result.SaveToFile（'F：\ProgramFiles\Embarcadero\dtx\Projects\Bmp-DIB\JPG2BMP.bmp'）;
除
FreeAndNil（Result）;
END；
结尾；
最终
FreeAndNil（JPG）;
结尾；
结尾；
procedure LoadImageFromStream（Stream：TStream; Image：TImage）;
var
wic：TWICImage;
位图：TBitmap;
开始
Stream.Position：= 0;
wic：= TWICImage.Create;
试试
wic.LoadFromStream（Stream）;
Image.Picture.Assign（wic）;
位图：= TBitmap.Create;
试试
Bitmap.PixelFormat：= pf24bit;
Bitmap.Width：= Image.Picture.Width;
Bitmap.Height：= Image.Picture.Height;
Bitmap.Canvas.Draw（0，0，Image.Picture.Graphic）;
Bitmap.SaveToFile（'F：\ProgramFiles\Embarcadero\dtx\Projects\Bmp-DIB\TWICImage.bmp'）;
最后
位图。
结尾；
最终
wic。免费；
结尾；
结尾；
过程RenderImage（const Filename：string）;
var
fs：TFileStream;
开始
fs：= TFileStream.Create（Filename，fmOpenRead）;
试试
LoadImageFromStream（fs，Form1.Image1）;
最终
fs。免费；
结尾；
结尾；
GetTickCount，用于所有经过测试的例程。
程序TForm1.Button1Click（Sender：TObject）;
var
MyDIB：TBitmap;
loadStr：字符串;
XStart，Xend：LongWord;
begin
loadStr：=‘F：\ProgramFiles\Embarcadero\dtx\Projects\Bmp-DIB\2018-10-17 14.04.23.jpg’；
XStart：= GetTickCount;
如果RadioGroup1.ItemIndex = 0则MyDIB：= ConvertJPG2BMP（loadStr）; // ConvertJPG2BMP（）
如果RadioGroup1.ItemIndex = 1则TestBmp（loadStr）;
如果RadioGroup1.ItemIndex = 2，则RenderImage（loadStr）; // TWICImage
如果RadioGroup1.ItemIndex = 3，则GetOleGraphic（loadStr）;
Xend：= GetTickCount;
Label1.Caption：= IntToStr（xEnd-XStart）+’：MS’；
结尾；
生成的图像仅与函数
I have this function that takes 4.2 seconds to convert a jpg to bmp.
Why it takes so long? Can I make if faster?
IrfanView loads and converts the file in only a fraction of that time.
I thought that is spends most of the time in JPG.LoadFromFile. But when I measured the time I was surprised to see it spends most of the time in BMP.Assing(JPG).
function ConvertJPG2BMP(CONST FileName: string): TBitmap;
VAR JPG: TJpegImage;
begin
Result:= NIL;
JPG:= TJpegImage.Create;
TRY
JPG.LoadFromFile(FileName);
if (JPG.Width > 0) AND (JPG.Width < 32768)
AND (JPG.Height> 0) AND (JPG.Height < 32768) then
begin
Result:= TBitmap.Create;
TRY
Result.HandleType:= bmDIB;
// Fuji_FinePix_F550.JPG [3200x1800] [1.44MB]
Result.Assign(JPG); <--- 4 seconds!!
EXCEPT
FreeAndNil(Result);
END;
end;
FINALLY
FreeAndNil(JPG);
end;
end;
Since I wanted to test the slightly older functions once, it is a good opportunity to do this now.
These have been changed a bit in the code below.
Somewhat adapted source code of OP's function ConvertJPG2BMP() (2512 : ms)
function ConvertJPG2BMP(CONST FileName: string): TBitmap;
VAR
JPG: TJpegImage;
begin
Result:= NIL;
JPG:= TJpegImage.Create;
TRY
JPG.LoadFromFile(FileName);
if (JPG.Width > 0) AND (JPG.Width < 32768)
AND (JPG.Height> 0) AND (JPG.Height < 32768) then
begin
Result:= TBitmap.Create;
TRY
Result.PixelFormat := pf24bit;
Result.Width := JPG.Width;
Result.Height := JPG.Height;
Result.HandleType:= bmDIB;
// 2018-10-17 14.04.23.jpg [2560x1920] [1.66MB]
Result.Assign(JPG);
Result.SaveToFile('F:\ProgramFiles\Embarcadero\dtx\Projects\Bmp-DIB\JPG2BMP.bmp');
EXCEPT
FreeAndNil(Result);
END;
end;
FINALLY
FreeAndNil(JPG);
end;
end;
The source for the TWICImage usage (296 : ms)
There is another class in Vcl.Graphics? called TWICImage that handles images supported by the Microsoft Imaging Component
Including BMP, GIF, ICO, JPEG, PNG, TIF and Windows Media Photo
procedure LoadImageFromStream(Stream: TStream; Image: TImage);
var
wic: TWICImage;
Bitmap: TBitmap;
begin
Stream.Position := 0;
wic := TWICImage.Create;
try
wic.LoadFromStream(Stream);
Image.Picture.Assign(wic);
Bitmap := TBitmap.Create;
try
Bitmap.PixelFormat := pf24bit;
Bitmap.Width := Image.Picture.Width;
Bitmap.Height := Image.Picture.Height;
Bitmap.Canvas.Draw(0, 0, Image.Picture.Graphic);
Bitmap.SaveToFile('F:\ProgramFiles\Embarcadero\dtx\Projects\Bmp-DIB\TWICImage.bmp');
finally
Bitmap.Free;
end;
finally
wic.Free;
end;
end;
procedure RenderImage(const Filename: string);
var
fs: TFileStream;
begin
fs := TFileStream.Create(Filename, fmOpenRead);
try
LoadImageFromStream(fs, Form1.Image1);
finally
fs.Free;
end;
end;
GetTickCount for all tested routines.
procedure TForm1.Button1Click(Sender: TObject);
var
MyDIB : TBitmap;
loadStr : string;
XStart,Xend : LongWord;
begin
loadStr := 'F:\ProgramFiles\Embarcadero\dtx\Projects\Bmp-DIB\2018-10-17 14.04.23.jpg';
XStart := GetTickCount;
if RadioGroup1.ItemIndex = 0 then MyDIB := ConvertJPG2BMP(loadStr);// ConvertJPG2BMP()
if RadioGroup1.ItemIndex = 1 then TestBmp(loadStr);
if RadioGroup1.ItemIndex = 2 then RenderImage(loadStr);// TWICImage
if RadioGroup1.ItemIndex = 3 then GetOleGraphic(loadStr);
Xend := GetTickCount;
Label1.Caption := IntToStr(xEnd-XStart) + ' : MS' ;
end;
The generated images are identical to the file size only from the function GetOleGraphic() is a smaller file produced with a worse resolution?
here the source used for the GetOleGraphic()
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