问题
If I open an image with open("image.jpg"), how can I get the RGB values of a pixel assuming I have the coordinates of the pixel?
Then, how can I do the reverse of this? Starting with a blank graphic, 'write' a pixel with a certain RGB value?
I would prefer if I didn't have to download any additional libraries.
回答1:
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.
回答2:
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
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
回答3:
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.
回答4:
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]
回答5:
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
回答6:
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.
回答7:
You can use pygame's surfarray module. This module has a 3d pixel array returning method called pixels3d(surface). I've shown usage below:
from pygame import surfarray, image, display
import pygame
import numpy #important to import
pygame.init()
image = image.load("myimagefile.jpg") #surface to render
resolution = (image.get_width(),image.get_height())
screen = display.set_mode(resolution) #create space for display
screen.blit(image, (0,0)) #superpose image on screen
display.flip()
surfarray.use_arraytype("numpy") #important!
screenpix = surfarray.pixels3d(image) #pixels in 3d array:
#[x][y][rgb]
for y in range(resolution[1]):
for x in range(resolution[0]):
for color in range(3):
screenpix[x][y][color] += 128
#reverting colors
screen.blit(surfarray.make_surface(screenpix), (0,0)) #superpose on screen
display.flip() #update display
while 1:
print finished
I hope been helpful. Last word: screen is locked for lifetime of screenpix.
回答8:
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.
回答9:
install PIL using the command "sudo apt-get install python-imaging" and run the following program. It will print RGB values of the image. If the image is large redirect the output to a file using '>' later open the file to see RGB values
import PIL
import Image
FILENAME='fn.gif' #image can be in gif jpeg or png format
im=Image.open(FILENAME).convert('RGB')
pix=im.load()
w=im.size[0]
h=im.size[1]
for i in range(w):
for j in range(h):
print pix[i,j]
回答10:
You could use the Tkinter module, which is the standard Python interface to the Tk GUI toolkit and you don't need extra download. See https://docs.python.org/2/library/tkinter.html.
(For Python 3, Tkinter is renamed to tkinter)
Here is how to set RGB values:
#from http://tkinter.unpythonic.net/wiki/PhotoImage
from Tkinter import *
root = Tk()
def pixel(image, pos, color):
"""Place pixel at pos=(x,y) on image, with color=(r,g,b)."""
r,g,b = color
x,y = pos
image.put("#%02x%02x%02x" % (r,g,b), (y, x))
photo = PhotoImage(width=32, height=32)
pixel(photo, (16,16), (255,0,0)) # One lone pixel in the middle...
label = Label(root, image=photo)
label.grid()
root.mainloop()
And get RGB:
#from http://www.kosbie.net/cmu/spring-14/15-112/handouts/steganographyEncoder.py
def getRGB(image, x, y):
value = image.get(x, y)
return tuple(map(int, value.split(" ")))
回答11:
import matplotlib.pyplot as plt
import matplotlib.image as mpimg
img=mpimg.imread('Cricket_ACT_official_logo.png')
imgplot = plt.imshow(img)
回答12:
from PIL import Image
def rgb_of_pixel(img_path, x, y):
im = Image.open(img_path).convert('RGB')
r, g, b = im.getpixel((x, y))
a = (r, g, b)
return a
回答13:
If you are looking to have three digits in the form of an RGB colour code, the following code should do just that.
i = Image.open(path)
pixels = i.load() # this is not a list, nor is it list()'able
width, height = i.size
all_pixels = []
for x in range(width):
for y in range(height):
cpixel = pixels[x, y]
all_pixels.append(cpixel)
This may work for you.
来源：https://stackoverflow.com/questions/138250/how-to-read-the-rgb-value-of-a-given-pixel-in-python