title: skimage convert to grayscale resulting to a black image
body: <p>I am scraping image and trying to convert them into grayscale. But if i view the image. It is plain black. Can someone tell me what is wrong with this? Thanks</p>
  
  <p>Here is my snippet</p>
  
  <pre><code>import cv2
  from skimage import io
  from skimage import data
  from skimage.color import rgb2gray
  
  #...some codes
  
  for i in elements:
      try:
          i.click()
      except ElementClickInterceptedException:
          driver.execute_script("window.scrollTo(0, document.body.scrollHeight);")
          i.click()
      url = driver.find_element_by_xpath('//*[@class="slider-list"]/div/img').get_attribute('src').replace('height=600','height=1200').replace('quality=70','quality=100')
      print (url)
      name = driver.find_element_by_xpath('//*[@class="slider-list"]/div/img').get_attribute('alt') + '.jpg'
  
      print (name)
      img = io.imread(url)
      new = rgb2gray(img)
      cv2.imwrite(os.path.join(fldrnm, name), new)
  </code></pre>