batch tiff to jpeg conversion script

[rti...@vt.edu]

Hope it's not inappropriate to post this here.

Could someone critique my code? I have no Python programmers in my
office to show this to. The script works OK, but should I do it
differently? I especially don't like how I check to see if jpegs exist.

The style may not be acceptable to some, but I'm concerned with
substance, not style. Is there a 'more appropriate' way to do this?

Thanks to all who take the time to give advice!

-----------------------------------------------------------------
import os
import os.path
#From PIL
import Image

def tiff_to_jpeg(path):

for root, dirs, files in os.walk(path):
for f in files:
if os.path.splitext(os.path.join(root,f))[1].lower() ==
".tif":

# If a jpeg is already present. Don't do anything.
if
os.path.isfile(os.path.splitext(os.path.join(root,f))[0] + ".jpg"):
print "A jpeg file already exists for %s" %f

# If a jpeg is *NOT* present, create one from the tiff.
else:
outfile = os.path.splitext(os.path.join(root,f))[0]
+ ".jpg"
try:
im = Image.open(os.path.join(root,f))
print "Generating jpeg for %s" %f
im.thumbnail(im.size)
im.save(outfile, "JPEG", quality=100)
except Exception, e:
print e

# Run Program
path = '.'
tiff_to_jpeg(path)

[Larry Bates]

The methodology seems just fine. You may (or may not) find
the following code easier to read (not tested):

for f in [file for file in files if file.lower().endswith('.tif')]:

# If a jpeg is already present. Don't do anything.

filename, extension=f.split('.')
jpgfile="%s.jpg" % filename
jpgpath=os.path.join(root, jpgfile)

# If a jpeg is *NOT* present, create one from the tiff.

if not os.path.isfile(jpgpath):

try:
im = Image.open(os.path.join(root,f))
print "Generating jpeg for %s" % f
im.thumbnail(im.size)

im.save(jpgpath, "JPEG", quality=100)

except Exception, e:
print e

continue

print "A jpeg file already exists for %s" % f

This code:

1) only processess .tif files
2) simplifies things by eliminating the splitext methods and
slicing operations.
3) eliminates else branch

-Larry Bates

[Peter Hansen]

rti...@vt.edu wrote:
> Hope it's not inappropriate to post this here.
>
> Could someone critique my code?

[snip]
> im.save(outfile, "JPEG", quality=100)

From an effbot posting on 13 Jul 2002:

'''JPEG quality 100 is overkill, btw -- it completely disables JPEG's
quantization stage, and "mainly of interest for experimental pur-
poses", according to the JPEG library documentation, which
continues:

"Quality values above about 95 are NOT recommended for
normal use; the compressed file size goes up dramatically
for hardly any gain in output image quality."

(full text below):

Should probably add something about this to the PIL docs...
'''

(As near as I can tell, so far, the last comment hasn't been followed
through on.)

-Peter

[rti...@vt.edu]

Hi Peter. The guy who takes the pictures uses Photoshop to convert
tiffs to jpegs one by one. When he does a 'Maxium Quality' conversion
in Photoshop and I do a 100% quality conversion with Python and PIL,
the two converted files are almost identical and this is what he
wants... that's the only reason I'm using 100% quality. Thanks for the
info!

[rti...@vt.edu]

Thanks for the example code Larry. It _is_ easier for me to read. I
like the way you split the file on '.' I may use that. Thanks again!

[Martin Miller]

Allow me interject two observations:

1) You should tell the guy using Photoshop what Peter pointed out
regarding the Jpeg Quality setting.

2) Although it wouldn't be as flexible as your Python script, it's
completely possible and fairly easy to automate such a conversion
within Photoshop using 'Actions', which are like recorded macros,
coupled with the Automate | Batch... submenu.

Best,
-Martin

[Peter Hansen]

Martin Miller wrote:
> rti...@vt.edu wrote:
>
>>Hi Peter. The guy who takes the pictures uses Photoshop to convert
>>tiffs to jpegs one by one. When he does a 'Maxium Quality' conversion
>>in Photoshop and I do a 100% quality conversion with Python and PIL,
>>the two converted files are almost identical and this is what he
>>wants... that's the only reason I'm using 100% quality. Thanks for the
>>info!
>
>
> Allow me interject two observations:
>
> 1) You should tell the guy using Photoshop what Peter pointed out
> regarding the Jpeg Quality setting.

Or consider using PNG files instead, which can do pretty decent lossless
compression, which might be what the guy really wants to do. I haven't
compared a 100% JPG with a PNG but it might be instructive.

-Peter

[Peter Hansen]

rti...@vt.edu wrote:
> Thanks for the example code Larry. It _is_ easier for me to read. I
> like the way you split the file on '.' I may use that. Thanks again!

Warning: that will fail on names with more than one "." in them. It's
generally best to use the provided tools for working with paths, in this
case os.path.splitext() which will do the right thing in any case (even
on names without extensions!).

-Peter

[rti...@vt.edu]

Just curious... is PhotoShop _really_ recursive? We have dozens of
levels of sub-folders where the pics have been sorted and thousands of
pics. That's one reason I used os.walk()

[Martin Miller]

Yes, in the sense that there is an "Include All Subfolders" option for
batch operation source files that recursively locates input files.
However, at least in the version I have (CS), there is no obvious way
to get it to recreate the input folder hierarchy with a different root
folder specified as the destination (all the output files get put in
single folder specified) -- something that could be fairly easily
accomplished using a Python script.

Since in this case you are doing file *conversions*, the output files
will have a different extension than the orginals, and can therefore
exist in the same folders (assuming there's enough disk space). This
makes it possible to record a "Save As" command in the Action which to
simply save the converted image back into the same folder as the
orginal in a different format, thus preserving the file & folder
layout.

Sorry, but I feel any more detail on the process would be getting way
too off-topic for this newsgroup. Feel free to contact me directly if
you would like to discuss in more detail how to do this sort of thing
from within Photoshop.

Best,
-Martin

[William Park]

rti...@vt.edu <rti...@vt.edu> wrote:
> Hope it's not inappropriate to post this here.
>
> Could someone critique my code? I have no Python programmers in my
> office to show this to. The script works OK, but should I do it
> differently? I especially don't like how I check to see if jpegs exist.
>
> The style may not be acceptable to some, but I'm concerned with
> substance, not style. Is there a 'more appropriate' way to do this?
>
> Thanks to all who take the time to give advice!

At the risk of being flamed... Have you tried ImageMagick utilities.
For example,
man convert

--
William Park <openge...@yahoo.ca>, Toronto, Canada
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