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Image Processing library (PIL). This is a package that you can import into python and it has quite a few methods that you can process image files with. There are loaders for the majority of the popular file formats The following import is required from PIL import Image

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Image processing library pil
Image Processing library (PIL)

  • This is a package that you can import into python and it has quite a few methods that you can process image files with. There are loaders for the majority of the popular file formats

  • The following import is required

  • from PIL import Image

  • The above works already in Anaconda. If you are building your own world using IDLE then you would need to download PIL and install in your environment.

Auto generates x values here!


Example Commands in PIL

The Image module is quite useful. Here are some examples

from PIL import Image

im= Image.open("bride.jpg") #Read in the image

im.rotate(45) #Returns a rotated image, 45 degrees

im.crop(box) # Returns a copy of a rect. sub-region

im.filter(filter) #Returns a copy of an image filtered by the given

#filter. For a list of available filters, see the ImageFilter module.

im.load() #Returns a high speed pixel access object.

im.resize() # Returns the image resized.

im.save(“Name”) #Save the image into file “Name”


structure of A 24 bit Image

Location=(col,row)

(14,14)

cols,rows=im.size

rows=18 and cols=35

Contents=(R,G,B) tuple i.e. (255,34,128)


Looking at every Pixel

In order to process each pixel in the image we need to use a double loop. Here is a simple example.

for c in range(3): #col values

for r in range(5): #row values

print c,r

0 0

0 1

0 2 col 0

0 3

0 4

1 0

1 1

1 2 col 1

1 3

1 4

2 0

2 1

2 2 col 2

2 3

2 4


Antialising
Antialising

  • This is a process that is used in image production that smooths out hard edges with a visual trick. Here is an example.

antialiased no antialising


Paint net antialising
paint.net antialising

Every image processing program has a button or icon to click to turn on/off

antialising. The above is paint.nets method. Note you must be in one of the

drawing tools, ie pen to see the control. Turn it off or on BEFORE you draw.


I created this image without antialising
I created this image without antialising

Lets turn this red to grey


Convert red pixels to gray by looping thru every pixel

import matplotlib.pyplot as plt

from PIL import Image

im = Image.open('thingsnoanti.png') # read in image

pix = im.load() #allows fast access for pixel access

cols,rows=im.size#get dimensions from size tuple

#look at every single pixel and if red turn it to gray. Capice?!

for r in range(rows):

for c in range(cols):

if (pix[c,r] == (255,0,0)): #if pixel is red

pix[c,r]=(220,220,220) #set it gray

plt.imshow(im)

plt.show()

Note that you can do anything you want to every pixel using the above method. Just change the blue lines.


Using filters
Using filters

  • The filter operations (BLUR, SMOOTH, SHARPEN etc) will loop thru the entire image for you.

Here is the result of blur

as applied to our original

image.


And here is the code
And here is the code

From ImageFilter module

BLUR

CONTOUR

DETAIL

EDGE_ENHANCE

EDGE_ENHANCE_MORE

EMBOSS

FIND_EDGES

SMOOTH

SMOOTH_MORE

SHARPEN

  • import matplotlib.pyplot as plt

  • from PIL import Image

  • from PIL import ImageFilter

  • im = Image.open('thingsnoanti.png')

  • plt.figure(1) #work on figure 1

  • plt.imshow(im) #show original image

  • plt.show()

  • im1 = im.filter(ImageFilter.BLUR) #lets blur it

  • plt.figure(2) #Work on figure 2

  • plt.imshow(im1) #show new image

  • plt.show()


Plot a histogram of a gray scale image
Plot a Histogram of a gray-scale image

  • import matplotlib.pyplot as plt

  • from PIL import Image

  • im = Image.open('sea.gif')

  • plt.figure(1)

  • plt.imshow(im) #show original image

  • plt.show()

  • hist = im.histogram()

  • #note that the hist here is a list not an image

  • plt.figure(2)

  • plt.plot(hist) #So we must plotthe list NOT imshow()

  • plt.show()



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