Counting pixels in image

[Thekid]

Hi,

I know I need to use PIL, but how would I count all of the red pixels in a given image? The image is simply a vertical red line on a black background.

import PIL
 
im = image.open("mypic.jpg")
im.getdata()
 

Something like that maybe but not sure how to get it to count the red pixels.

[bvdet]

Let us assume a pixel is red if each RGB value is in excess of 200.

from PIL import Image
import operator
 
img = Image.open('your_image')
 
# Count the pixels having RGB values in defined range
 
upper = (255,255,255)
lower = (200,200,200)
 
print len([pixel for pixel in img.getdata() \
           if False not in map(operator.lt,lower,pixel) \
           and False not in map(operator.gt,upper,pixel)])

[kudos]

I would do it this way:

from PIL import Image
im  = Image.new("RGBA",(512,512))
 
# create a funny picture... (with some red)
 
for i in range(512):
 for j in range(512):
  im.putpixel((j,i),(j^i)%256)
 
# calculate the number of "reds"
cnr = 0
for i in range(512):
 for j in range(512):
  if((im.getpixel((j,i)))[0] == 255):
   cnr+=1
 
print "nr of red pixels : " + str(cnr)
print "presentage of red pixels : " + str((cnr / (512.0*512.0))*100.0) + "%"
 
im.save("pattern.png")  # look at it, it looks funny
 

[bvdet]

That's cool kudos. Thanks for sharing.

[bvdet]

I did a red count on my avatar.

from PIL import Image
import operator
 
img = Image.open('image.png')
 
upper = (256,40,40)
lower = (190,0,0)
 
print '\n'.join([str(pixel) for pixel in img.getdata() \
                 if False not in map(operator.lt,lower,pixel) \
                 and False not in map(operator.gt,upper,pixel)])
 
# Output:
>>> (210, 13, 7)
(202, 21, 7)
(201, 9, 9)
(198, 11, 11)
(196, 26, 6)
(198, 15, 15)
>>>