如何循环浏览图像中的单个像素并输出每行的最高RGB值像素？

Question

I'm trying to import an image file, such as file.bmp, read the RGB values of each pixel in the image, and then output the highest RGB valued pixel (the brightest pixel) for each row to the screen. Any suggestions on how to do it using Python?

Answer 1

Well, you could use scipy.misc.imread to read the image and manipulate it like so:

import scipy.misc
file_array = scipy.misc.imread("file.bmp")

def get_brightness(pixel_tuple):
   return sum([component*component for component in pixel_tuple])**.5 # distance from (0, 0, 0)

row_maxima = {}
height, width = len(file_array), len(file_array[0])
for y in range(height):
  for x in range(width):
    pixel = tuple(file_array[y][x]) # casting it to a tuple so it can be stored in the dict
    if y in row_maxima and get_brightness(pixel) > row_maxima[y]:
      row_maxima[y] = pixel
    if y not in row_maxima:
      row_maxima[y] = pixel
print row_maxima

Answer 2

You can make a lot of use of the power of numpy here. Note that the code below outputs "brightness" in the range [0, 255].

#!/bin/env python

import numpy as np
from scipy.misc import imread

#Read in the image
img = imread('/users/solbrig/smooth_test5.png')

#Sum the colors to get brightness
brightness = img.sum(axis=2) / img.shape[2]

#Find the maximum brightness in each row
row_max = np.amax(brightness, axis=1)
print row_max

If you think your image might have an alpha layer, you can do this:

#!/bin/env python

import numpy as np
from scipy.misc import imread

#Read in the image
img = imread('/users/solbrig/smooth_test5.png')

#Pull off alpha layer
if img.shape[2] == 4:
    alph = img[:,:,3]/255.0
    img = img[:,:,0:3]
else:
    alph = np.ones(img.shape[0:1])

#Sum the colors to get brightness
brightness = img.sum(axis=2) / img.shape[2]
brightness *= alph

#Find the maximum brightness in each row
row_max = np.amax(brightness, axis=1)
print row_max