TJpegImage is very slow,why?
lazarus / 39-Graphics

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yayongm · 2012-08-28 12:35

when open a 640X480X32bit jpeg file, the flowing code is very slow in
lazarus(<45/s), but very fast in delphi(>20000/s) ,why and how to fix?


var
  dTime: DWord;
  iCount: Integer;
  AMS: TMemoryStream;
  AJpg: TJpegImage;
  ADlg: TOpenDialog;
  sJpg: string;
begin
  ADlg := TOpenDialog.Create(nil);
  AMS := TMemoryStream.Create;
  try
    if not ADlg.Execute then
      Exit;
    AMS.LoadFromFile(ADlg.FileName);
    SetLength(sJpg, AMS.Size);
    AMS.Position := 0;
    AMS.Read(sJpg[1], AMS.Size);
  finally
    FreeAndNil(AMS);
    FreeAndNil(ADlg);
  end;

  dTime := GetTickCount;
  iCount := 0;
  while (GetTickCount - dTime) < 5000 do
  begin
    AMS := TMemoryStream.Create;
    AJpg := TJpegImage.Create;
    try
      AMS.Write(sJpg[1], Length(sJpg));
      AMS.Position := 0;
      AJpg.LoadFromStream(AMS);
    finally
      FreeAndNil(AJpg);
      FreeAndNil(AMS);
    end;
    Inc(iCount);
  end;
  Memo1.Lines.Add(Format('JpegFile Result: %f/s', [iCount / 5]));
end;

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User137 · 2012-08-28 15:44

I got little different, but similar result with my 640x480 jpg.

Code: [Select]Lazarus 1.1 SVN:
JpegFile Result: 34,60/s
JpegFile Result: 34,60/s

-Just file-load:
JpegFile Result: 34,40/s
JpegFile Result: 34,20/s
Code: [Select]Delphi 7:
JpegFile Result: 2008,00/s
JpegFile Result: 2000,40/s

-Just file-load:
JpegFile Result: 4726,00/s
JpegFile Result: 4747,60/s
For that "Just file-load" test i changed the loop to:
Code: [Select]  while (GetTickCount - dTime) < 5000 do begin
    AJpg := TJpegImage.Create;
    AJpg.LoadFromFile('test.jpg');
    AJpg.Free;
    Inc(iCount);
  end;
I wish this could be fixed too. Kind of important when dealing with
graphics, or games. Have to test with PNG too though... JPG's are a
useless relic of old times

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BigChimp · 2012-08-28 15:49

IIRC, the default fpc image handling routines were built for
stability, not speed.
I seem to remember that being mentioned on some wiki page.

I'm sure there must be alternatives, once again, have a look on the
wiki.

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User137 · 2012-08-28 15:58

Code: [Select]  while (GetTickCount - dTime) < 5000 do begin
    Apng := TPortableNetworkGraphic.Create; // fpc version
    Apng.LoadFromFile('test.png');
    Apng.Free;
    Inc(iCount);
  end;
  Memo1.Lines.Add(Format('PngFile Result: %f/s', [iCount / 5]));
Delphi:
Code: [Select]PngFile Result: 45,80/s
PngFile Result: 45,80/s
Lazarus:
Code: [Select]PngFile Result: 24,40/s
PngFile Result: 24,40/s
No big differences there, but Borland didn't implement it for Delphi 7
so that's 3rd party lib.

And on second thought, the speed is enough for game loading times.
This cannot be bottleneck, and 24 this big PNG's is a massive pile of
pixels.

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marcov · 2012-08-28 16:18

Quote from: BigChimp on August 28, 2012, 05:49:01 pmIIRC, the default
fpc image handling routines were built for stability, not speed.
I seem to remember that being mentioned on some wiki page.

While true, Lazarus iirc doesn't use that but an own type based on
FPC's abstract image class. (TlazIntfImage iirc)

Lazintfimage doesn't have the main inefficiency of the FPC class,
namely that every pixel is 64-bit.

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yayongm · 2012-08-29 01:39

To all:
    The code will be run in arm cpu, but it is too slow to cancel...
    so, if the performance is not important, why we use native code
and lazarus?
    sorry...

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BigChimp · 2012-08-29 07:19

@yayongm: have you actually looked at the wiki for other JPEG
libraries? I'm sure there are some (e.g. Vampyre)... IIRC, some even
in native Pascal.

Others will probably use a jpg .dll/.so, but if that offers big speed
improvements, and the library in question is very common, it may be
worth choosing that.

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yayongm · 2012-08-30 07:12

@BigChimp,Thank you. I have install Vampyre and the code is changed:

{$I ImagingOptions.inc}

.....

var
  dTime: DWord;
  iCount: Integer;
  AMS: TMemoryStream;
  AJpg: TMultiImage;
  ADlg: TOpenDialog;
  sJpg: string;
begin
  ADlg := TOpenDialog.Create(nil);
  AMS := TMemoryStream.Create;
  try
    if not ADlg.Execute then
      Exit;
    AMS.LoadFromFile(ADlg.FileName);
    SetLength(sJpg, AMS.Size);
    AMS.Position := 0;
    AMS.Read(sJpg[1], AMS.Size);
  finally
    FreeAndNil(AMS);
    FreeAndNil(ADlg);
  end;

  dTime := GetTickCount;
  iCount := 0;
  while (GetTickCount - dTime) < 5000 do
  begin
    AMS := TMemoryStream.Create;
    AJpg := TMultiImage.Create;
    try
      AMS.Write(sJpg[1], Length(sJpg));
      AMS.Position := 0;
      AJpg.LoadMultiFromStream(AMS);
    finally
      FreeAndNil(AJpg);
      FreeAndNil(AMS);
    end;
    Inc(iCount);
  end;
  Caption := Format('JpegFile Result: %f/s', [iCount / 5]);
end;

================
But the result is:58.20/s

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reinerr · 2012-10-25 00:12

Are you sure its actually working? The code in your loop appears to
fill a buffer with the text of a file name and then load a jpeg from
this text. Perhaps you wanted to do something like
AMS.LoadFromFile(ADlg.FileName); instead of AMS.Write(sJpg[1],
Length(sJpg)); ??? Although since your stream doesn't have a valid
jpeg header I would have expected it to bomb out much quicker.

Code: [Select]    AMS := TMemoryStream.Create;
    AJpg := TJpegImage.Create;
    try
      AMS.Write(sJpg[1], Length(sJpg)); // this is putting the file
name text into the stream
      AMS.Position := 0;
      AJpg.LoadFromStream(AMS); // this is trying to load an image
from text

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mdalacu · 2012-10-25 07:58

I also am trying to find a solution to load fast multiple jpgs from
stream (from multiple ip cams). I have tried native jpeg image and
also vampyre ... both pretty are pretty slow.
In 2 years i have not found a solution for this, in Lazarus. Maybe
someone competent could look into this issue and solve it, it will
have a big impact in many areas.
Thank you.