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<refmeta>
<refentrytitle>Using `vipsthumbnail`</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>libvips</refmiscinfo>
</refmeta>
<refnamediv>
<refname>`vipsthumbnail`</refname>
<refpurpose>Introduction to `vipsthumbnail`, with examples</refpurpose>
</refnamediv>
This page shows a few examples of using VIPS from Python.
# Average a region of interest box on an image
``` python
#!/usr/bin/env python
import sys
import gi
gi.require_version('Vips', '8.0')
from gi.repository import Vips
roix = 10
roiy = 10
roiw = 64
roih = 64
image = Vips.Image.new_from_file(sys.argv[1])
roi = image.crop(roix, roiy, roiw, roih)
print 'average: ', roi.avg()
```
# VIPS and PIL
This script moves an image between PIL and VIPS.
``` python
#!/usr/bin/python
import sys
from vipsCC import *
import Image
# try this 1,000 times and check for leaks
for i in range (0,1000):
vim = VImage.VImage (sys.argv[1])
# do some processing in vips ... cut out a small piece of image
vim = vim.extract_area (500, 500, 100, 100)
# make a PIL image
# we use Image.frombuffer (), so PIL is using vim's memory
# you need to be very careful not to destroy vim until you're done with pim
# ideally you should make a proxy class that wraps this lifetime problem up
mode = VImage.PIL_mode_from_vips (vim)
size = (vim.Xsize (), vim.Ysize ())
data = vim.tobuffer ()
pim = Image.frombuffer (mode, size, data, 'raw', mode, 0, 1)
# rotate 12 degrees with PIL
pim = pim.rotate (12, Image.BILINEAR, 1)
# back to vips again
# PIL doesn't have a tobuffer method, so we have to use tostring to copy the
# data out of PIL and then fromstring to copy back into VIPS
str = pim.tostring ()
bands, format, type = VImage.vips_from_PIL_mode (pim.mode)
width, height = pim.size
vim2 = VImage.VImage.fromstring (str, width, height, bands, format)
# finally write from vips
vim2.write (sys.argv[2])
```
Leak testing
------------
This loads an image, does some simple processing, and saves again. Handy for leak testing.
``` python
#!/usr/bin/python
import sys
# just need this for leaktesting
import gc
from vipsCC import *
if len (sys.argv) != 3:
print 'usage:', sys.argv[0], 'inputimage outputimage'
sys.exit (1)
try:
a = VImage.VImage (sys.argv[1])
b = a.invert ()
c = b.lin ([1,2,3],[4,5,6])
m = VMask.VIMask (3, 3, 1, 0,
[-1, -1, -1,
-1, 8, -1,
-1, -1, -1])
d = a.conv (m)
d.write (sys.argv[2])
except VError.VError, e:
e.perror (sys.argv[0])
# we can get properties of VImage too
print 'inputimage is', a.Xsize (), 'pixels across'
print 'starting shutdown ...'
del b
del a
del c
del d
del m
# sometimes have to do several GCs to get them all, not sure why
for i in range(10):
gc.collect ()
print 'shutdown!'
print 'leaked IMAGEs:'
VImage.im__print_all ()
print 'done ... hopefully you saw no leaks'
```
Build image mosaic
------------------
This loads a lot of images (RGB or greyscale) and pastes them at random positions in a 10,000 by 10,000 pixel output image. 8-bit only, but it'd be easy to change that.
``` python
#!/usr/bin/python
import sys
import random
from vipsCC import *
# the size of the image we build
size = 10000
try:
if len(sys.argv) < 3:
print 'usage:', sys.argv[0], 'outfile infile1 ...'
sys.exit (1)
# make the background image
bg = VImage.VImage.black (size, size, 3)
# paste each argument in
for file in sys.argv[2:]:
im = VImage.VImage (file)
# is this a mono image? convert to RGB by joining three of them
# together
if im.Bands() == 1:
im = im.bandjoin (im).bandjoin (im)
x = random.randint (0, size - im.Xsize () - 1)
y = random.randint (0, size - im.Ysize () - 1)
bg = bg.insert_noexpand (im, x, y)
# write result
bg.write (sys.argv[1])
except VError.VError, e:
e.perror (sys.argv[0])
```
Build image pyramid
-------------------
This makes a tiled image pyramid, with each tile in a separate 512x512 pixel file.
``` python
#!/usr/bin/python
import sys
from vipsCC import *
tilesize = 512
maxlevel = 100
try:
im = VImage.VImage (sys.argv[1])
for level in range (maxlevel, -1, -1):
print "Creating tiles for level", level
# loop to create the tiles
for y in range (0, im.Ysize(), tilesize):
for x in range (0, im.Xsize(), tilesize):
filename = '%dx%d_y%d.jpg' % (level, x / tilesize, y / tilesize)
# clip tilesize against image size
width = min (im.Xsize () - x, tilesize)
height = min (im.Ysize () - y, tilesize)
# expand edge tiles up to the full tilesize ... Google maps likes this
# im.extract_area (x, y, width, height).embed(0, 0, 0, tilesize, tilesize).write(filename)
# let edge tiles be smaller than the full tile size, tiff tiling prefers this
im.extract_area (x, y, width, height).write (filename)
# was there only a single tile? we are done
if im.Xsize() <= tilesize and im.Ysize() <= tilesize:
break
# create next pyramid level in RAM
shrink = im.rightshift_size (1, 1, im.BandFmt())
im = shrink.write (VImage.VImage ("temp", "t"))
except VError.VError, e:
e.perror (sys.argv[0])
```
Rename DICOM images using header fields
---------------------------------------
DICOM images commonly come in an awful directory hierarchy named as something like images/a/b/e/z04. There can be thousands of files and it can be very hard to find the one you want.
This utility copies files to a single flat directory, naming them using fields from the DICOM header. You can actually find stuff! Useful.
``` python
#!/usr/bin/python
import sys
import re
import os
import shutil
from vipsCC import *
if len (sys.argv) != 3:
print 'rename DICOM files using tags from the header'
print 'usage:'
print '\t%s srcdir destdir' % sys.argv[0]
print 'the directory tree below srcdir is searched, all files are'
print 'renamed and put into destdir in a flat list'
sys.exit (1)
srcdir = sys.argv[1]
destdir = sys.argv[2]
if not os.access (destdir, os.F_OK | os.R_OK | os.W_OK | os.X_OK):
os.mkdir (destdir)
def get_field (vim, field):
result = vim.meta_get_string (field)
# remove any \n etc.
result = re.sub ("\n", "", result)
# remove any leading or trailing spaces
result = re.sub (" $", "", result)
result = re.sub ("^ ", "", result)
return result
id_name = "magick-dcm:Patient'sID"
modality_name = "magick-dcm:Modality"
series_name = "magick-dcm:SeriesNumber"
instance_name = "magick-dcm:Instance(formerlyImage)Number"
date_name = "magick-dcm:ImageDate"
n_processed = 0
for (dirpath, dirnames, filenames) in os.walk (srcdir):
for file in filenames:
path = os.path.join (dirpath, file)
try:
vim = VImage.VImage (path)
except VError.VError, e:
print 'unable to open', path
continue
try:
id = get_field (vim, id_name)
modality = get_field (vim, modality_name)
series = get_field (vim, series_name)
instance = get_field (vim, instance_name)
date = get_field (vim, date_name)
except VError.VError, e:
print 'unable to get fields from header', path
continue
match = re.match ("(\d\d\d\d)(\d\d)(\d\d)", date)
date = match.group (1) + "." + match.group (2) + "." + match.group (3)
newname = id + "." + modality + "." + series + "." + instance + "." + date + ".IMA"
shutil.copyfile(path, os.path.join (destdir, newname))
n_processed += 1
print '\t(%d files processed)' % n_processed
```