DZone Snippets: jpeg code

Convert Canon RAW ( .CRW) to jpeg

sandos (John Bäckstrand) — Fri, 27 Jun 2008 07:01:38 GMT

This is adapted from http://www.howtofixcomputers.com/forums/digital-photo/my-humble-contribution-wrapper-script-dcraw-linux-4360.html to enable (I think) higher quality interpolation in dcraw and higher quality JPEGs.



DCRAW="dcraw -w -c "

while [ $# -ge 1 ]

do

OJPEG=$(echo $1| perl -pe 's/\.crw$//i' | tr 'A-Z' 'a-z')'.jpeg'

echo "${DCRAW} $1 | cjpeg > ${OJPEG}"

${DCRAW} -q 3 $1 | cjpeg -quality 95 > ${OJPEG} || echo " *PROBLEM*"

# transfer EXIF data from the original raw file

exiftool -overwrite_original -TagsFromFile "$1" "${OJPEG}" >/dev/null

# preserve timestamps as much as possible

# touch -r "$1" "${OJPEG}"

dcraw -z "${OJPEG}"

shift

done

Read & Write JPEG COM and EXIF metadata

korakot (Korakot Chaovavanich) — Tue, 27 Dec 2005 20:07:51 GMT

This snippet is similar to my previous one.



import jpeg



#read/write JPEG comments (aka the COM area)

jpeg.getComments(file)

jpeg.setComments(txt, file)



#read/write some EXIF data

e = jpeg.getExif(file)   #an Exif object

e2 = jpeg.getExif2(file) #an Exif extension segment as Exif instance too



#quick getter

d = e.dict()

print d['image description']

e.display()  #function to print all tags and their value, type, etc.



#some tags with an explicit interface, some are writable

print e.description

e.description = "my nice picture"



#generic read function

print e.get(0x010e)  #value for a tag number you know

print e.get(0x010e, value=False) #get the tag as a Tag instance



#generic write function

e.set(0x010e, "my nice picture", e.ifd0, 2)

    #e.ifd0, e.exif, e.gps or e.interop, represents the IFD the tag belongs to

    #and 2 represents the fact that the tag is of ASCII type

    #see www.exif.org specifications for details



#iterate

for tag in e:

   print tag.getValue() #value parsed

   print tag.value      #value raw

   tag.setValue(100)    #change it



#save the changed Exif segment back into the image file

jpeg.setExif(e, file)

See more details, and download the module here.

Reading and writing image metadata

korakot (Korakot Chaovavanich) — Thu, 29 Sep 2005 22:09:49 GMT

The IPTCInfo module allows you to add/edit metadata
to your image. You can download it from here.

Reading



from iptcinfo import IPTCInfo

info = IPTCInfo('test.jpg')

print info.keywords, info.supplementalCategories, info.contacts

caption = info.data['caption/abstract']

Add/Edit



info = IPTCInfo('test.jpg')

info.data['caption/abstract'] = 'Witty caption here'

info.data['supplemental category'] = ['portrait']

info.save()

info.saveAs('test_out.jpg')  # keep original safe

Installing libjpeg on OS X

peter (Peter Cooperx) — Tue, 05 Apr 2005 20:21:21 GMT

Get http://www.ijg.org/files/jpegsrc.v6b.tar.gz, and then:

tar zxvf jpegsrc.v6b.tar.gz

cd jpeg-6b

cp /usr/share/libtool/config.sub .

cp /usr/share/libtool/config.guess .

./configure --enable-shared --enable-static

make

sudo make install

sudo ranlib /usr/local/lib/libjpeg.a