[fpc-pascal] Why is FPImage dog slow in reading jpeg's?

[michael.vancanneyt at wisa.be]

Try the following code:

Img:=TFPMemoryImage.Create(0,0);
Img.UsePalette:=False;
Img.loadFromFile(FileList[i]);

That should work much faster. The reason is probably that the default image
created by the reader uses a palette, which is of course dog slow when reading 
large images.

Michael.

On Mon, 30 May 2011, Ben Smith wrote:

> Hi,
>
> I wrote this console utility app in 5 minutes. All it is supposed to
> do, is iterate over *.jpg images (65 at the moment) in a folder (no
> recursive searches), and generate a snipped of HTML that I need to
> paste into my wives website.
>
> I first thought my utility app is in some recursive loop or something
> because the output didn't appear instantly - like I thought it would.
>
> I added some debug output between the generate HTML. To my surprise
> the FPImage code reading a 35Kb jpg file takes +- 8 seconds and a 65KB
> file takes +- 30 seconds - on a Quad Core machine! WTF???
>
> Is this normal? Is FPImage really that slow reading small roughly
> 650x450 pixel jpg images?  Or am I doing something unbelievably
> stupid? :-/
>
> The reason I'm reading in the jpg files is so I can get their Width
> and Height values. Avg. jpeg file sizes are between 35-45KB, and
> largest file size is 65KB.
>
> Here is the relevant code snippet....
>
> var
>  imgreader: TFPReaderJPEG;
>  stream: TFileStream;
>  img:TFPCustomImage;
>
> ....
>
>  writeln('processing file: ', filelist[i]);
>  stream := TFileStream.Create(filelist[i], fmOpenRead);
>  writeln(1);
>  imgreader := TFPReaderJPEG.Create;
>  writeln(2, FormatDateTime(' hh:mm:ss.zz', Now) + '  (start reading)');
>  img := imgreader.ImageRead(stream, nil);
>  writeln(3, FormatDateTime(' hh:mm:ss.zz', Now) + '  (done)');
>
>
>
>
> Here is the program output... Note the timestamps between start
> reading and done reading (lines marked with '2' and '3').
>
>
> -------------------[ start ]---------------------------
> $ ./project1 img/babies/full
> Finished search. Found 65 matches
> ---------------------------------------
> <div id="thumbnails">
> <table cellspacing="10">
> <tr align="center" valign="middel">	<!--  Row starts  -->
> <td>
> processing file: img/babies/full/babies.01.jpg
> 1
> 2 16:00:30.210  (start reading)
> 3 16:00:38.338  (done)
> <img src="img/babies/full/babies.01.jpg" alt="" id="screen1"
> class="imglarge" onmouseout="reducethumb(1); return false;"
> onclick="reducethumb(1); return false;">
> <img src="img/babies/thumbs/babies.01.jpg" alt="" class="imgsmall"
> id="thumb1" onclick="expandthumb(1, 650, 413);">
> </td>
> </tr>
> <tr align="center" valign="middel">	<!--  Row starts  -->
> <td>
> processing file: img/babies/full/babies.02.jpg
> 1
> 2 16:00:38.338  (start reading)
> 3 16:01:10.447  (done)
> <img src="img/babies/full/babies.02.jpg" alt="" id="screen2"
> class="imglarge" onmouseout="reducethumb(2); return false;"
> onclick="reducethumb(2); return false;">
> <img src="img/babies/thumbs/babies.02.jpg" alt="" class="imgsmall"
> id="thumb2" onclick="expandthumb(2, 650, 435);">
> </td>
> </tr>
> <tr align="center" valign="middel">	<!--  Row starts  -->
> <td>
> processing file: img/babies/full/babies.03.jpg
> 1
> 2 16:01:10.447  (start reading)
> 3 16:01:28.859  (done)
> <img src="img/babies/full/babies.03.jpg" alt="" id="screen3"
> class="imglarge" onmouseout="reducethumb(3); return false;"
> onclick="reducethumb(3); return false;">
> <img src="img/babies/thumbs/babies.03.jpg" alt="" class="imgsmall"
> id="thumb3" onclick="expandthumb(3, 405, 650);">
> </td>
> </tr>
> <tr align="center" valign="middel">	<!--  Row starts  -->
> <td>
> processing file: img/babies/full/babies.04.jpg
> 1
> 2 16:01:28.859  (start reading)
>
> ....snip....
> -------------------[ end ]---------------------------
>
>
>
> -- 
>
>            Ben.
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