Images and matrices¶

Cheat sheet how to converge image into arrays and the other way around.

In [1]:
from jyquickhelper import add_notebook_menu

Out[1]:
run previous cell, wait for 2 seconds

PIL: simple operations¶

Open¶

In [2]:
from PIL import Image
img = Image.open("images1.jpg")
img

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In [3]:
img.size

Out[3]:
(289, 175)
In [4]:
img.resize((50, 50))

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Combine¶

In [5]:
new_img = Image.new('RGB', (img.size[0]*2, img.size[1]))
new_img.paste(img, (0,0))
new_img.paste(img, (img.size[0],0))
new_img

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In [6]:
def combine(*imgs, mode='RGB', vert=False):
if vert:
sizesx = [im.size[0] for im in imgs]
sizesy = [im.size[1] for im in imgs]
new_img = Image.new(mode, (max(sizesx), sum(sizesy)))
y = 0
for im in imgs:
new_img.paste(im, (0, y))
y += im.size[1]
else:
sizesx = [im.size[0] for im in imgs]
sizesy = [im.size[1] for im in imgs]
new_img = Image.new(mode, (sum(sizesx), max(sizesy)))
x = 0
for im in imgs:
new_img.paste(im, (x, 0))
x += im.size[0]
return new_img

combine(img, img)

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In [7]:
combine(img, img, vert=True)

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PIL to array¶

It is a colored image so we have 3 images into 3, red, blue, green.

In [8]:
import numpy
array = numpy.array(img.getdata(), dtype=numpy.uint8).reshape(img.size[1], img.size[0], 3)
array.shape

Out[8]:
(175, 289, 3)
In [9]:
array.dtype

Out[9]:
dtype('uint8')

more simple way

In [10]:
array = numpy.array(img)
array.shape

Out[10]:
(175, 289, 3)

Array to array transposed¶

In [11]:
array.transpose((2, 1, 0)).shape

Out[11]:
(3, 289, 175)

Array to PIL¶

In [12]:
from PIL import Image
img2 = Image.fromarray(array)
img2

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Split colors¶

In [13]:
im_r, im_b, im_g = img.split()
combine(im_r, im_b, im_g, mode="L")

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YCbCr¶

In [14]:
img_ycbcr = img.convert('YCbCr')
img_ycbcr.size

Out[14]:
(289, 175)
In [15]:
img_y, img_cb, img_cr = img_ycbcr.split()
img_y.size

Out[15]:
(289, 175)
In [16]:
combine(img_y, img_cb, img_cr, mode="L")

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Zoom¶

In [17]:
img2.resize((720, 120))

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In [18]: