python - 如何循环遍历图像中的单个像素并输出每行的最高 RGB 值像素？

Question

我正在尝试导入一个图像文件，例如 file.bmp，读取图像中每个像素的 RGB 值，然后将每行的最高 RGB 值像素（最亮的像素）输出到屏幕。关于如何使用 Python 执行此操作的任何建议？

Answer 1

好吧，您可以使用scipy.misc.imread它来读取图像并像这样操作它：

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

您可以在这里充分利用 numpy 的强大功能。请注意，下面的代码在 [0, 255] 范围内输出“亮度”。

#!/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

如果你认为你的图像可能有一个 alpha 层，你可以这样做：

#!/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