制作数据集（一）：从google image中批量下载图片

背景：因为项目需要，希望制作一个由平面、反光材质的照片组成的数据集，如木质纹理的桌面、门面， 平坦的瓷砖地板、墙面，反光的金属表面等等。但是找不到能满足需求的数据集，所以制作了自己的数据集

方法：首先po出原文链接：https://www.pyimagesearch.com/2017/12/04/how-to-create-a-deep-learning-dataset-using-google-images/

• 在谷歌图片中搜索想要下载的图片，这里仅限谷歌浏览器，国内可以通过GHelper插件使用谷歌，读者可以自行百度，如何安装GHelper
• 如下，
• 1、先在谷歌图片中搜索"C Ronaldo",
• 2、滚动页面，直到加载完所有你想下载的图片
• 3、使用“ctrl + shift + j”调出JavaScript控制台
• 4、将下面的代码复制到控制台，随即出现一个名为‘urls.txt’的下载页面，选择合适的位置下载即可
• 

• /**
   * simulate a right-click event so we can grab the image URL using the
   * context menu alleviating the need to navigate to another page
   *
   * attributed to @jmiserez: http://pyimg.co/9qe7y
   *
   * @param   {object}  element  DOM Element
   *
   * @return  {void}
   */
  function simulateRightClick( element ) {
      var event1 = new MouseEvent( 'mousedown', {
          bubbles: true,
          cancelable: false,
          view: window,
          button: 2,
          buttons: 2,
          clientX: element.getBoundingClientRect().x,
          clientY: element.getBoundingClientRect().y
      } );
      element.dispatchEvent( event1 );
      var event2 = new MouseEvent( 'mouseup', {
          bubbles: true,
          cancelable: false,
          view: window,
          button: 2,
          buttons: 0,
          clientX: element.getBoundingClientRect().x,
          clientY: element.getBoundingClientRect().y
      } );
      element.dispatchEvent( event2 );
      var event3 = new MouseEvent( 'contextmenu', {
          bubbles: true,
          cancelable: false,
          view: window,
          button: 2,
          buttons: 0,
          clientX: element.getBoundingClientRect().x,
          clientY: element.getBoundingClientRect().y
      } );
      element.dispatchEvent( event3 );
  }
  
  /**
   * grabs a URL Parameter from a query string because Google Images
   * stores the full image URL in a query parameter
   *
   * @param   {string}  queryString  The Query String
   * @param   {string}  key          The key to grab a value for
   *
   * @return  {string}               value
   */
  function getURLParam( queryString, key ) {
      var vars = queryString.replace( /^?/, '' ).split( '&' );
      for ( let i = 0; i < vars.length; i++ ) {
          let pair = vars[ i ].split( '=' );
          if ( pair[0] == key ) {
              return pair[1];
          }
      }
      return false;
  }
  
  
  
  /**
   * Generate and automatically download a txt file from the URL contents
   *
   * @param   {string}  contents  The contents to download
   *
   * @return  {void}
   */
  function createDownload( contents ) {
      var hiddenElement = document.createElement( 'a' );
      hiddenElement.href = 'data:attachment/text,' + encodeURI( contents );
      hiddenElement.target = '_blank';
      hiddenElement.download = 'urls.txt';
      hiddenElement.click();
  }
  
  /**
   * grab all URLs va a Promise that resolves once all URLs have been
   * acquired
   *
   * @return  {object}  Promise object
   */
  function grabUrls() {
      var urls = [];
      return new Promise( function( resolve, reject ) {
          var count = document.querySelectorAll(
              '.isv-r a:first-of-type' ).length,
              index = 0;
          Array.prototype.forEach.call( document.querySelectorAll(
              '.isv-r a:first-of-type' ), function( element ) {
              // using the right click menu Google will generate the
              // full-size URL; won't work in Internet Explorer
              // (http://pyimg.co/byukr)
              simulateRightClick( element.querySelector( ':scope img' ) );
              // Wait for it to appear on the <a> element
              var interval = setInterval( function() {
                  if ( element.href.trim() !== '' ) {
                      clearInterval( interval );
                      // extract the full-size version of the image
                      let googleUrl = element.href.replace( /.*(?)/, '$1' ),
                          fullImageUrl = decodeURIComponent(
                              getURLParam( googleUrl, 'imgurl' ) );
                      if ( fullImageUrl !== 'false' ) {
                          urls.push( fullImageUrl );
                      }
                      // sometimes the URL returns a "false" string and
                      // we still want to count those so our Promise
                      // resolves
                      index++;
                      if ( index == ( count - 1 ) ) {
                          resolve( urls );
                      }
                  }
              }, 10 );
          } );
      } );
  }
  
  /**
   * Call the main function to grab the URLs and initiate the download
   */
  grabUrls().then( function( urls ) {
      urls = urls.join( '
  ' );
      createDownload( urls );
  } );

• Python 爬取图片
• 新建一个“download_images.py”文件，并在虚拟环境下，安装你需要安装的包，并将下面的代码复制到你的“download_images.py”文件

• # import the necessary packages
  from imutils import paths
  import argparse
  import requests
  import cv2
  import os

  # construct the argument parse and parse the arguments
  ap = argparse.ArgumentParser()
  ap.add_argument("-u", "--urls", required=True,
      help="path to file containing image URLs")    # 设置刚刚保存的urls.txt路径
  ap.add_argument("-o", "--output", required=True,
      help="path to output directory of images")    # 设置图片保存的路径
  args = vars(ap.parse_args())
  # grab the list of URLs from the input file, then initialize the
  # total number of images downloaded thus far
  rows = open(args["urls"]).read().strip().split("
  ")
  total = 0

  # loop the URLs
  for url in rows:
      try:
          # try to download the image
          r = requests.get(url, timeout=60)
          # save the image to disk
          p = os.path.sep.join([args["output"], "{}.jpg".format(
              str(total).zfill(8))])
          f = open(p, "wb")
          f.write(r.content)
          f.close()
          # update the counter
          print("[INFO] downloaded: {}".format(p))
          total += 1
      # handle if any exceptions are thrown during the download process
      except:
          print("[INFO] error downloading {}...skipping".format(p))

  # loop over the image paths we just downloaded
  for imagePath in paths.list_images(args["output"]):
      # initialize if the image should be deleted or not
      delete = False
      # try to load the image
      try:
          image = cv2.imread(imagePath)
          # if the image is `None` then we could not properly load it
          # from disk, so delete it
          if image is None:
              delete = True
      # if OpenCV cannot load the image then the image is likely
      # corrupt so we should delete it
      except:
          print("Except")
          delete = True
      # check to see if the image should be deleted
      if delete:
          print("[INFO] deleting {}".format(imagePath))
          os.remove(imagePath)

  $ python download_images.py --urls urls.txt --output images/santa    # 设置路径
  [INFO] downloaded: images/santa/00000000.jpg
  [INFO] downloaded: images/santa/00000001.jpg
  [INFO] downloaded: images/santa/00000002.jpg
  [INFO] downloaded: images/santa/00000003.jpg
  ...
  [INFO] downloaded: images/santa/00000519.jpg
  [INFO] error downloading images/santa/00000519.jpg...skipping
  [INFO] downloaded: images/santa/00000520.jpg
  ...
  [INFO] deleting images/santa/00000211.jpg
  [INFO] deleting images/santa/00000199.jpg