There are several ways to open images:
All of these operations are provided by the constructor of Image class.
The most frequently used way is just to open an image by its filename. Image‘s constructor can take the parameter named filename:
from __future__ import print_function
from wand.image import Image
with Image(filename='pikachu.png') as img:
print('width =', img.width)
print('height =', img.height)
Note
It must be passed by keyword argument exactly. Because the constructor has many parameters that are exclusive to each other.
There is a keyword argument named file as well, but don’t confuse it with filename. While filename takes a string of a filename, file takes a input stream (file-like object).
If an image to open cannot be located by a filename but can be read through input stream interface (e.g. opened by os.popen(), contained in StringIO, read by urllib2.urlopen()), it can be read by Image constructor’s file parameter. It takes all file-like objects which implements read() method:
from __future__ import print_function
from urllib2 import urlopen
from wand.image import Image
response = urlopen('https://stylesha.re/minhee/29998/images/100x100')
try:
with Image(file=response) as img:
print('format =', img.format)
print('size =', img.size)
finally:
response.close()
In the above example code, response object returned by urlopen() function has read() method, so it also can be used as an input stream for a downloaded image.
If you have just a binary string (str) of the image, you can pass it into Image constructor’s blob parameter to read:
from __future__ import print_function
from wand.image import Image
with open('pikachu.png') as f:
image_binary = f.read()
with Image(blob=image_binary) as img:
print('width =', img.width)
print('height =', img.height)
It is a way of the lowest level to read an image. There will probably not be many cases to use it.
If you have an image already and have to copy it for safe manipulation, use clone() method:
from wand.image import Image
with Image(filename='pikachu.png') as original:
with original.clone() as converted:
converted.format = 'png'
# operations on a converted image...
For some operations like format converting or cropping, there are safe methods that return a new image of manipulated result like convert() or slicing operator. So the above example code can be replaced by:
from wand.image import Image
with Image(filename='pikachu.png') as original:
with original.convert('png') as converted:
# operations on a converted image...
When it’s read from a binary string or a file object, you can explicitly give the hint which indicates file format of an image to read — optional format keyword is for that:
from wand.image import Image
with Image(blob=image_binary, format='ico') as image:
print(image.format)
New in version 0.2.1: The format parameter to Image constructor.
To open an empty image, you have to set its width and height:
from wand.image import Image
with Image(width=200, height=100) as img:
img.save(filename='200x100-transparent.png')
Its background color will be transparent by default. You can set background argument as well:
from wand.color import Color
from wand.image import Image
with Color('red') as bg:
with Image(width=200, height=100, background=bg) as img:
img.save(filename='200x100-red.png')
New in version 0.2.2: The width, height, and background parameters to Image constructor.