running imagemagick convert (console application) from python

Question

I am trying to rasterize some fonts using imagemagick with this command which works fine from a terminal:

convert -size 30x40 xc:white -fill white -fill black -font "fonts\Helvetica Regular.ttf" -pointsize 40 -gravity South -draw "text 0,0 'O'" draw_text.gif

Running the same command using subprocess to automate it does not work:

try:
    cmd= ['convert','-size','30x40','xc:white','-fill','white','-fill','black','-font','fonts\Helvetica Regular.ttf','-pointsize','40','-gravity','South','-draw',"text 0,0 'O'",'draw_text.gif']
    #print(cmd)
    subprocess.check_output(cmd,shell=True,stderr=subprocess.STDOUT)
except CalledProcessError as e:
    print(e)
    print(e.output)

.

Command '['convert', '-size', '30x40', 'xc:white-fill', 'white', '-fill', 'black', '-font', 'fonts\\Helvetica Regular.ttf', '-pointsize', '40', '-gravity', 'South', '-draw', "text 0,0 'O'", 'draw_text.gif']' returned non-zero exit status 4
b'Invalid Parameter - 30x40\r\n'

@gahooa For some reason, I have never been able to run anything without shell=True. I tried it with shell=False but that gives me the same error. Anyway, it is not unsafe because I am not using any untrusted input. — Navin
– Navin, Commented Feb 22, 2013 at 4:51
For starters, take str.join(' ', cmd) and copy+paste that to the command line to see if it still works. — gahooa
– gahooa, Commented Feb 22, 2013 at 4:54
@gahooa That works if I quote the fonts\Helve... and text 0,0 'O'. I think this is normal because the quotes are only there because of the space in the argument and the shell strips away the quotes before passing them to the program — Navin
– Navin, Commented Feb 22, 2013 at 4:59

Navin · Accepted Answer · 2013-10-30 22:48:33Z

9

I figured it out: It turns out that windows has its own convert.exe program in PATH.

The following code prints b'C:\\Windows\\System32\\convert.exe\r\n':

try:
    print(subprocess.check_output(["where",'convert'],stderr=subprocess.STDOUT,shell=True))
except CalledProcessError as e:
    print(e)
    print(e.output)

Running the same code in a terminal shows that imagemagick's convert shadows Windows' convert:

C:\Users\Navin>where convert                                                    
C:\Program Files\ImageMagick-6.8.3-Q16\convert.exe                              
C:\Windows\System32\convert.exe

.

I did not restart python after installing ImageMagick so its PATH still pointed to the Windows version.

Using the full path works:

try:
    cmd= ['C:\Program Files\ImageMagick-6.8.3-Q16\convert','-size','30x40','xc:white','-fill','white','-fill','black','-font','fonts\Helvetica Regular.ttf','-pointsize','40','-gravity','South','-draw',"text 0,0 'P'",'draw_text.gif']
    print(str.join(' ', cmd))
    print('stdout: {}'.format(subprocess.check_output(cmd,shell=True,stderr=subprocess.STDOUT)))
except CalledProcessError as e:
    print(e)
    print(e.output)

edited Oct 30, 2013 at 22:48

answered Feb 22, 2013 at 5:07

Navin

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2 Comments

André Duarte Over a year ago

I don't know why but in OSX(10.11) works only without shell=True.

Navin Over a year ago

@AndréDuarte Yep, I did the same thing 4 years ago when I asked this question. Though since then, I realized that ImageMagick is a piece of crap and I'd much rather use an image library with a real API.

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