How to read the RGB value of a given pixel in Python?

Question

It's probably best to use the Python Image Library to do this which I'm afraid is a separate download.

The easiest way to do what you want is via the load() method on the Image object which returns a pixel access object which you can manipulate like an array:

from PIL import Image

im = Image.open('dead_parrot.jpg') # Can be many different formats.
pix = im.load()
print im.size  # Get the width and hight of the image for iterating over
print pix[x,y]  # Get the RGBA Value of the a pixel of an image
pix[x,y] = value  # Set the RGBA Value of the image (tuple)
im.save('alive_parrot.png')  # Save the modified pixels as .png

Alternatively, look at ImageDraw which gives a much richer API for creating images.

Using Pillow (which works with Python 3.X as well as Python 2.7+), you can do the following:

from PIL import Image
im = Image.open('image.jpg', 'r')
width, height = im.size
pixel_values = list(im.getdata())

Now you have all pixel values. If it is RGB or another mode can be read by im.mode. Then you can get pixel (x, y) by:

pixel_values[width*y+x]

Alternatively, you can use Numpy and reshape the array:

>>> pixel_values = numpy.array(pixel_values).reshape((width, height, 3))
>>> x, y = 0, 1
>>> pixel_values[x][y]
[ 18  18  12]

A complete, simple to use solution is

# Third party modules
import numpy
from PIL import Image


def get_image(image_path):
    """Get a numpy array of an image so that one can access values[x][y]."""
    image = Image.open(image_path, "r")
    width, height = image.size
    pixel_values = list(image.getdata())
    if image.mode == "RGB":
        channels = 3
    elif image.mode == "L":
        channels = 1
    else:
        print("Unknown mode: %s" % image.mode)
        return None
    pixel_values = numpy.array(pixel_values).reshape((width, height, channels))
    return pixel_values


image = get_image("gradient.png")

print(image[0])
print(image.shape)

Smoke testing the code

You might be uncertain about the order of width / height / channel. For this reason I've created this gradient:

The image has a width of 100px and a height of 26px. It has a color gradient going from #ffaa00 (yellow) to #ffffff (white). The output is:

[[255 172   5]
 [255 172   5]
 [255 172   5]
 [255 171   5]
 [255 172   5]
 [255 172   5]
 [255 171   5]
 [255 171   5]
 [255 171   5]
 [255 172   5]
 [255 172   5]
 [255 171   5]
 [255 171   5]
 [255 172   5]
 [255 172   5]
 [255 172   5]
 [255 171   5]
 [255 172   5]
 [255 172   5]
 [255 171   5]
 [255 171   5]
 [255 172   4]
 [255 172   5]
 [255 171   5]
 [255 171   5]
 [255 172   5]]
(100, 26, 3)

Things to note:

• The shape is (width, height, channels)
• The image[0], hence the first row, has 26 triples of the same color

PyPNG - lightweight PNG decoder/encoder

Although the question hints at JPG, I hope my answer will be useful to some people.

Here's how to read and write PNG pixels using PyPNG module:

import png, array

point = (2, 10) # coordinates of pixel to be painted red

reader = png.Reader(filename='image.png')
w, h, pixels, metadata = reader.read_flat()
pixel_byte_width = 4 if metadata['alpha'] else 3
pixel_position = point[0] + point[1] * w
new_pixel_value = (255, 0, 0, 0) if metadata['alpha'] else (255, 0, 0)
pixels[
  pixel_position * pixel_byte_width :
  (pixel_position + 1) * pixel_byte_width] = array.array('B', new_pixel_value)

output = open('image-with-red-dot.png', 'wb')
writer = png.Writer(w, h, **metadata)
writer.write_array(output, pixels)
output.close()

PyPNG is a single pure Python module less than 4000 lines long, including tests and comments.

PIL is a more comprehensive imaging library, but it's also significantly heavier.

As Dave Webb said:

Here is my working code snippet printing the pixel colours from an image:

import os, sys
import Image

im = Image.open("image.jpg")
x = 3
y = 4

pix = im.load()
print pix[x,y]

photo = Image.open('IN.jpg') #your image
photo = photo.convert('RGB')

width = photo.size[0] #define W and H
height = photo.size[1]

for y in range(0, height): #each pixel has coordinates
    row = ""
    for x in range(0, width):

        RGB = photo.getpixel((x,y))
        R,G,B = RGB  #now you can use the RGB value

Image manipulation is a complex topic, and it's best if you do use a library. I can recommend gdmodule which provides easy access to many different image formats from within Python.

There's a really good article on wiki.wxpython.org entitled Working With Images. The article mentions the possiblity of using wxWidgets (wxImage), PIL or PythonMagick. Personally, I've used PIL and wxWidgets and both make image manipulation fairly easy.