PdfImg macro runs with 100% cpu load

I tried on my five year old celeron Linux Laptop the files

• http://www.engr.uconn.edu/~zshi/course/cse5095/doc/spru198j_programmers_guide.pdf
• http://www.adobe.com/devnet/pdf/pdf_reference.html

Convertnig to PNG worked for me on all files within seconds.

Because I have no Windows (ticket 9842 comment14) I am not able see wheather it is a problem of convert itself or on convert on windows (64bit Win Server 2003 R2) or on your installation.

It doesn't matter what the reason is, though likely it's because of any circumstances in convert or Ghostscript. I just want you to add a something like a flag "LowerPriorityThanNormal?" to your system call of 'convert' because you cannot control anymore how much impact that external call has on the system.

Find out how to start a sub process with lower priority here: http://docs.python.org/release/3.0.1/library/subprocess.html

Replying to falkb:

Find out how to start a sub process with lower priority here: http://docs.python.org/release/3.0.1/library/subprocess.html

replace

sts = os.system("convert" + " myarg")

with

p = Popen("convert" + " myarg", shell=True)
sts = os.waitpid(p.pid, 0)
setpriority(p.pid,1)

by using this helper function from http://code.activestate.com/recipes/496767-set-process-priority-in-windows:

def setpriority(pid=None,priority=1):
    """ Set The Priority of a Windows Process.  Priority is a value between 0-5 where
        2 is normal priority.  Default sets the priority of the current
        python process but can take any valid process ID. """
        
    import win32api,win32process,win32con
    
    priorityclasses = [win32process.IDLE_PRIORITY_CLASS,
                       win32process.BELOW_NORMAL_PRIORITY_CLASS,
                       win32process.NORMAL_PRIORITY_CLASS,
                       win32process.ABOVE_NORMAL_PRIORITY_CLASS,
                       win32process.HIGH_PRIORITY_CLASS,
                       win32process.REALTIME_PRIORITY_CLASS]
    if pid == None:
        pid = win32api.GetCurrentProcessId()
    handle = win32api.OpenProcess(win32con.PROCESS_ALL_ACCESS, True, pid)
    win32process.SetPriorityClass(handle, priorityclasses[priority])

I also asked about the problem (convert on Windows much slower than on Linux) in another forum and they say you should use a special parameter to avoid trashing the workstation:

convert -limit area 0 foo.pdf foo.png

Replying to falkb:

I also asked about the problem (convert on Windows much slower than on Linux) in another forum

see [11408]

can you work on windows server now?

I testes on windows 32Bit XP SP2 and cant report your Problems.

If you satisfied with the resolution, please close the ticket.

Thanks, your new [11408] should solve the memory problem since you can force the entire PDF to disk rather than memory by adding -limit area 1 to the command line call. At least a direct command line with that parameter didn't let explode the memory usage anymore.

Stay tuned for activities in the ImageMagick forum thread, I gave them the debug output of the slow convert. Still the conversion of a 441 pages PDF takes 15 minutes at 100% CPU load here in spite of your seen fast conversion of the same file. I'm going to wait for the result of that problem analysis, and maybe a solution for the problem, before I start thinking about closing this ticket.

Take a look at the ImageMagick forum discussion thread. They say it could be sufficient to just call Ghostscript instead of ImageMagick, and they describe how to set the proper Ghostscript commandline call. Just using Ghostscript without IM would speed conversion up, too. What do you think about it?

Replying to falkb:

Take a look at the ImageMagick forum discussion thread. They say it could be sufficient to just call Ghostscript instead of ImageMagick, and they describe how to set the proper Ghostscript commandline call. Just using Ghostscript without IM would speed conversion up, too. What do you think about it?

Could you change your plugin to use Ghostscript than ImageMagick?

After the continued discussion it turns out the direct using of Ghostscript is about 8 times faster than the same via ImageMagick (see http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=20574&start=15), e.g. 3 minutes instead of 25 minutes. And ImageMagick is just for throughputting the data with a bad bottleneck on Windows. You can even better control the conversion behaviour, for instance choose -sDEVICE=pnggray instead of -sDEVICE=pngalpha and the conversion time reduces by 2 minutes more to only 1 minute! Furthermore, the memory usage is much less than converting over ImageMagick (90MB vs. 800MB++).

Replying to falkb:

Could you change your plugin to use Ghostscript than ImageMagick?

ursaw, did you try the replacing of image magick by direct use of ghostscript as suggested by falkb in his forum posting 2012-03-22T06:20:30+00:00? it's true that's pretty much faster 'cause im has a terrible implementation of passing the data to gs. ---Dirk