Ruby on Rails XPath Json Scraping Images

2019-04-29 07:39发布

站内文章 / Ruby
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问题:

I'm trying to scrape images from websites. I'm using Nokogiri and XPath so far with limited success. For a typical website whose HTML has img and src, I can use:

 tmp2 = Nokogiri::HTML(open(site_url))
 tmp2.xpath("//img/@src").each do |src|
   ...do whatever
 end

However, some sites like Amazon and eBay only trigger certain images with javascript. If I look at the code, I can see the data in arrays. For example, from Amazon (source: http://www.amazon.com/Threads-Thought-Womens-Dreams-X-Small/dp/B00T46V758/ref=sr_1_5?s=apparel&ie=UTF8&qid=1433555447&sr=1-5):

    <script type="text/javascript">
P.when('jQuery', 'cf').execute(function($, cf){
  P.load.js('http://z-ecx.images-amazon.com/images/G/01/browser-scripts/imageBlock-udp-airy/imageBlock-udp-airy-4060168860._V1_.js');
});

P.when('A', 'jQuery', 'ImageBlockATF', 'cf').register('ImageBlockBTF', function(A, $, imageBlockATF, cf){
  var data = {"indexToColor":[],"burjImageBlock":0,"isSwatchHoverConsistent":1,"heroFocalPoint":null,"visualDimensions":["color_name"],"productGroupID":"apparel_display_on_website","newVideoMissing":0,"useIV":0,"useClickZoom":null,"useChildVideos":0,"numColors":7,"logMetrics":0,"defaultColor":"initial","airyConfig":{"enableContinuousPlay":null,"installFlashButtonText":"Install Flash Player","contentTitle":null,"autoplayCutOffTimeSeconds":null,"ageGate":{"monthNames":["January","February","March","April","May","June","July","August","September","October","November","December"],"deniedPrompt":"We're sorry. You are not old enough to watch this video.","submitText":"Submit","prompt":"This video is not intended for all audiences. What date were you born?"},"videoAds":null,"videoUnsupportedPrompt":"Sorry, this video is unsupported on this browser.","desiredMode":null,"swfUrl":"http://g-ecx.images-amazon.com/images/G/01/vap/video/airy2/prod/2.0.1102.0/flash/AiryBasicRenderer._V304902271_.swf","isAutoplayEnabled":null,"installFlashPrompt":"Adobe Flash Player is required to watch this video.","isLiveStream":null,"regionCode":"NA","contentId":null,"playbackErrorPrompt":"Sorry, an error has occurred while attempting video playback. Please try again later.","contentMinAge":null,"isForesterTrackingDisabled":null,"streamingUrls":null,"parentId":null,"foresterMetadataParams":{"client":"Dpx","requestId":"1MX7VHFRVAS6TWY64BXC","marketplaceId":"ATVPDKIKX0DER","session":"182-9511970-7757812","method":"Apparel.ImageBlock"},"jsUrl":"http://z-ecx.images-amazon.com/images/G/01/vap/video/airy2/prod/2.0.1102.0/js/airy.chromeless._V304902265_.js"},"mainImageMaxSizes":null,"staticStrings":{"playVideo":"Click to play video","rollOverToZoom":"Roll over image to zoom in","images":"Images","video":"video","clickToZoom":"Click on image to zoom in","touchToZoom":"Touch the image to zoom in","videos":"Videos","close":"Close","pleaseSelect":"Please select","clickToExpand":"Click to open expanded view","allMedia":"All Media"},"notThumbnailClickImmersiveView":1,"gIsNewTwister":1,"title":"Threads 4 Thought Women's Tabitha Basic Tank Top","ivRepresentativeAsin":{"6":"B00T46V76W","4":"B00WM3O7ES","1":"B00T46YZES","3":"B00WM3NLPE","2":"B00T46VD16","5":"B00T46VGXQ"},"mainImageSizes":[[342,445],[385,500],[425,550],[466,606],[522,679]],"isQuickview":0,"ipadVideoSizes":[[340,444],[384,500]],"colorToAsin":{"Coral Dreams":{"asin":"B00T46V76W"},"Heather Grey":{"asin":"B00WM3NLPE"},"Black":{"asin":"B00T46YZES"},"White":{"asin":"B00T46VGXQ"},"Deep Blue Sea":{"asin":"B00T46VD16"},"Sea Glass":{"asin":"B00WM3O7ES"}},"thumbExperimentEnabledValue":1,"showLITBOnClick":0,"videoSizes":[[342,445],[384,500]],"stretchyGoodnessWidth":[1280,1440,1640,1800],"autoplayVideo":0,"hoverZoomIndicator":"","sitbReftag":"","useHoverZoom":1,"staticImages":{"zoomOut":"http://g-ecx.images-amazon.com/images/G/01/detail-page/cursors/zoom-out._V184888738_.bmp","hoverZoomIcon":"http://g-ecx.images-amazon.com/images/G/01/img11/apparel/UX/DP/icon_zoom._V138923886_.png","zoomIn":"http://g-ecx.images-amazon.com/images/G/01/detail-page/cursors/zoom-in._V184888790_.bmp","zoomLensBackground":"http://g-ecx.images-amazon.com/images/G/01/apparel/rcxgs/tile._V211431200_.gif","videoThumbIcon":"http://g-ecx.images-amazon.com/images/G/01/Quarterdeck/en_US/images/video._V183716339_SX38_SY50_CR,0,0,38,50_.gif","spinner":"http://g-ecx.images-amazon.com/images/G/01/ui/loadIndicators/loading-large_labeled._V192238949_.gif","zoomInCur":"http://g-ecx.images-amazon.com/images/G/01/detail-page/cursors/zoomIn._V323082799_.cur","videoSWFPath":"http://g-ecx.images-amazon.com/images/G/01/Quarterdeck/en_US/video/20110518115040892/Video._V178668404_.swf","arrow":"http://g-ecx.images-amazon.com/images/G/01/javascripts/lib/popover/images/light/sprite-vertical-popover-arrow._V186877868_.png","zoomOutCur":"http://g-ecx.images-amazon.com/images/G/01/detail-page/cursors/zoomOut._V323082798_.cur"},"videos":[],"gPreferChildVideos":0,"altsOnLeft":1,"ivImageSetKeys":{"Coral Dreams":"6","Heather Grey":"3","Black":"1","initial":0,"White":"5","Deep Blue Sea":"2","Sea Glass":"4"},"useHoverZoomIpad":"","isUDP":1,"alwaysIncludeVideo":0,"widths":[1280,1440,1640,1800],"maxAlts":7,"useChromelessVideoPlayer":1,"mainImageHeightPartitions":null};
  data["customerImages"] = eval('[]');
  data["colorImages"] = {"Coral Dreams":[{"large":"http://ecx.images-amazon.com/images/I/41FGlhksmtL.jpg","variant":"MAIN","hiRes":"http://ecx.images-amazon.com/images/I/81iXQbkcpiL._UL1500_.jpg","thumb":"http://ecx.images-amazon.com/images/I/41FGlhksmtL._SR38,50_.jpg","main":{"http://ecx.images-amazon.com/images/I/81iXQbkcpiL._UX466_.jpg":["466","606"],"http://ecx.images-amazon.com/images/I/81iXQbkcpiL._UX522_.jpg":["522","679"],"http://ecx.images-amazon.com/images/I/81iXQbkcpiL._UY550_.jpg":["423","550"],"http://ecx.images-amazon.com/images/I/81iXQbkcpiL._UX342_.jpg":["342","445"],"http://ecx.images-amazon.com/images/I/81iXQbkcpiL._UY500_.jpg":["385","500"]}},{"large":"http://ecx.images-amazon.com/images/I/41XR9o0cV-L.jpg","variant":"BACK","hiRes":"http://ecx.images-amazon.com/images/I/81bVmFiRu0L._UL1500_.jpg","thumb":"http://ecx.images-amazon.com/images/I/41XR9o0cV-L._SR38,50_.jpg","main":{"http://ecx.images-amazon.com/images/I/81bVmFiRu0L._UY500_.jpg":["385","500"],"http://ecx.images-amazon.com/images/I/81bVmFiRu0L._UX522_.jpg":["522","679"],"http://ecx.images-amazon.com/images/I/81bVmFiRu0L._UX342_.jpg":["342","445"],"http://ecx.images-amazon.com/images/I/81bVmFiRu0L._UX466_.jpg":["466","606"],"http://ecx.images-amazon.com/images/I/81bVmFiRu0L._UY550_.jpg":["423","550"]}}],"Heather Grey":[{"large":"http://ecx.images-amazon.com/images/I/41f-8R8Eu-L.jpg","variant":"MAIN","hiRes":"http://ecx.images-amazon.com/images/I/81dTYkBL%2BxL._UL1500_.jpg","thumb":"http://ecx.images-amazon.com/images/I/41f-8R8Eu-L._SR38,50_.jpg","main":{"http://ecx.images-amazon.com/images/I/81dTYkBL%2BxL._UX466_.jpg":["466","606"],"http://ecx.images-amazon.com/images/I/81dTYkBL%2BxL._UY500_.jpg":["385","500"],"http://ecx.images-amazon.com/images/I/81dTYkBL%2BxL._UY550_.jpg":["423","550"],"http://ecx.images-amazon.com/images/I/81dTYkBL%2BxL._UX522_.jpg":["522","679"],"http://ecx.images-amazon.com/images/I/81dTYkBL%2BxL._UX342_.jpg":["342","445"]}},{"large":"http://ecx.images-amazon.com/images/I/41gLiFBbcdL.jpg","variant":"BACK","hiRes":"http://ecx.images-amazon.com/images/I/81ua3AXCpJL._UL1500_.jpg","thumb":"http://ecx.images-amazon.com/images/I/41gLiFBbcdL._SR38,50_.jpg","main":{"http://ecx.images-amazon.com/images/I/81ua3AXCpJL._UX342_.jpg":["342","445"],"http://ecx.images-amazon.com/images/I/81ua3AXCpJL._UY550_.jpg":["423","550"],"http://ecx.images-amazon.com/images/I/81ua3AXCpJL._UY500_.jpg":["385","500"],"http://ecx.images-amazon.com/images/I/81ua3AXCpJL._UX522_.jpg":["522","679"],"http://ecx.images-amazon.com/images/I/81ua3AXCpJL._UX466_.jpg":["466","606"]}}],"Black":[{"large":"http://ecx.images-amazon.com/images/I/41BxSpfEM7L.jpg","variant":"MAIN","hiRes":"http://ecx.images-amazon.com/images/I/81%2BTW8762BL._UL1500_.jpg","thumb":"http://ecx.images-amazon.com/images/I/41BxSpfEM7L._SR38,50_.jpg","main":{"http://ecx.images-amazon.com/images/I/81%2BTW8762BL._UY550_.jpg":["423","550"],"http://ecx.images-amazon.com/images/I/81%2BTW8762BL._UX342_.jpg":["342","445"],"http://ecx.images-amazon.com/images/I/81%2BTW8762BL._UX522_.jpg":["522","679"],"http://ecx.images-amazon.com/images/I/81%2BTW8762BL._UY500_.jpg":["385","500"],"http://ecx.images-amazon.com/images/I/81%2BTW8762BL._UX466_.jpg":["466","606"]}},{"large":"http://ecx.images-amazon.com/images/I/41Gf%2BW-cPTL.jpg","variant":"BACK","hiRes":"http://ecx.images-amazon.com/images/I/81SJwuaCspL._UL1500_.jpg","thumb":"http://ecx.images-amazon.com/images/I/41Gf%2BW-cPTL._SR38,50_.jpg","main":{"http://ecx.images-amazon.com/images/I/81SJwuaCspL._UY500_.jpg":["385","500"],"http://ecx.images-amazon.com/images/I/81SJwuaCspL._UX522_.jpg":["522","679"],"http://ecx.images-amazon.com/images/I/81SJwuaCspL._UX342_.jpg":["342","445"],"http://ecx.images-amazon.com/images/I/81SJwuaCspL._UX466_.jpg":["466","606"],"http://ecx.images-amazon.com/images/I/81SJwuaCspL._UY550_.jpg":["423","550"]}}],"White":[{"large":"http://ecx.images-amazon.com/images/I/41tElK2wPKL.jpg","variant":"MAIN","hiRes":"http://ecx.images-amazon.com/images/I/81kKgU75rIL._UL1500_.jpg","thumb":"http://ecx.images-amazon.com/images/I/41tElK2wPKL._SR38,50_.jpg","main":{"http://ecx.images-amazon.com/images/I/81kKgU75rIL._UY550_.jpg":["423","550"],"http://ecx.images-amazon.com/images/I/81kKgU75rIL._UX522_.jpg":["522","679"],"http://ecx.images-amazon.com/images/I/81kKgU75rIL._UY500_.jpg":["385","500"],"http://ecx.images-amazon.com/images/I/81kKgU75rIL._UX342_.jpg":["342","445"],"http://ecx.images-amazon.com/images/I/81kKgU75rIL._UX466_.jpg":["466","606"]}},{"large":"http://ecx.images-amazon.com/images/I/31lEDIs4cqL.jpg","variant":"BACK","hiRes":"http://ecx.images-amazon.com/images/I/81OBgvbUR7L._UL1500_.jpg","thumb":"http://ecx.images-amazon.com/images/I/31lEDIs4cqL._SR38,50_.jpg","main":{"http://ecx.images-amazon.com/images/I/81OBgvbUR7L._UX466_.jpg":["466","606"],"http://ecx.images-amazon.com/images/I/81OBgvbUR7L._UX342_.jpg":["342","445"],"http://ecx.images-amazon.com/images/I/81OBgvbUR7L._UX522_.jpg":["522","679"],"http://ecx.images-amazon.com/images/I/81OBgvbUR7L._UY500_.jpg":["385","500"],"http://ecx.images-amazon.com/images/I/81OBgvbUR7L._UY550_.jpg":["423","550"]}}],"Deep Blue Sea":[{"large":"http://ecx.images-amazon.com/images/I/41oNq3KmSGL.jpg","variant":"MAIN","hiRes":"http://ecx.images-amazon.com/images/I/81MtZtmxVLL._UL1500_.jpg","thumb":"http://ecx.images-amazon.com/images/I/41oNq3KmSGL._SR38,50_.jpg","main":{"http://ecx.images-amazon.com/images/I/81MtZtmxVLL._UX342_.jpg":["342","445"],"http://ecx.images-amazon.com/images/I/81MtZtmxVLL._UX522_.jpg":["522","679"],"http://ecx.images-amazon.com/images/I/81MtZtmxVLL._UY550_.jpg":["423","550"],"http://ecx.images-amazon.com/images/I/81MtZtmxVLL._UY500_.jpg":["385","500"],"http://ecx.images-amazon.com/images/I/81MtZtmxVLL._UX466_.jpg":["466","606"]}},{"large":"http://ecx.images-amazon.com/images/I/41AJgd1OuYL.jpg","variant":"BACK","hiRes":"http://ecx.images-amazon.com/images/I/81uLEksrYFL._UL1500_.jpg","thumb":"http://ecx.images-amazon.com/images/I/41AJgd1OuYL._SR38,50_.jpg","main":{"http://ecx.images-amazon.com/images/I/81uLEksrYFL._UX342_.jpg":["342","445"],"http://ecx.images-amazon.com/images/I/81uLEksrYFL._UY500_.jpg":["385","500"],"http://ecx.images-amazon.com/images/I/81uLEksrYFL._UX522_.jpg":["522","679"],"http://ecx.images-amazon.com/images/I/81uLEksrYFL._UX466_.jpg":["466","606"],"http://ecx.images-amazon.com/images/I/81uLEksrYFL._UY550_.jpg":["423","550"]}}],"Sea Glass":[{"large":"http://ecx.images-amazon.com/images/I/418vg-re8oL.jpg","variant":"MAIN","hiRes":"http://ecx.images-amazon.com/images/I/81YgtD-bEwL._UL1500_.jpg","thumb":"http://ecx.images-amazon.com/images/I/418vg-re8oL._SR38,50_.jpg","main":{"http://ecx.images-amazon.com/images/I/81YgtD-bEwL._UX342_.jpg":["342","445"],"http://ecx.images-amazon.com/images/I/81YgtD-bEwL._UX522_.jpg":["522","679"],"http://ecx.images-amazon.com/images/I/81YgtD-bEwL._UX466_.jpg":["466","606"],"http://ecx.images-amazon.com/images/I/81YgtD-bEwL._UY500_.jpg":["385","500"],"http://ecx.images-amazon.com/images/I/81YgtD-bEwL._UY550_.jpg":["423","550"]}},{"large":"http://ecx.images-amazon.com/images/I/41lcpC41VSL.jpg","variant":"BACK","hiRes":"http://ecx.images-amazon.com/images/I/814%2B6ZLwIxL._UL1500_.jpg","thumb":"http://ecx.images-amazon.com/images/I/41lcpC41VSL._SR38,50_.jpg","main":{"http://ecx.images-amazon.com/images/I/814%2B6ZLwIxL._UY500_.jpg":["385","500"],"http://ecx.images-amazon.com/images/I/814%2B6ZLwIxL._UX342_.jpg":["342","445"],"http://ecx.images-amazon.com/images/I/814%2B6ZLwIxL._UX522_.jpg":["522","679"],"http://ecx.images-amazon.com/images/I/814%2B6ZLwIxL._UX466_.jpg":["466","606"],"http://ecx.images-amazon.com/images/I/814%2B6ZLwIxL._UY550_.jpg":["423","550"]}}]};
  data["heroImage"] = {};
  data["landingAsinColor"] = 'Coral Dreams';
  data["shouldApplyResizeFix"] = false;

  return data;
});

</script>

The filenames I want to grab don't have src (i.e. http://ecx.images-amazon.com/images/I/81%2BTW8762BL.UY500.jpg) In this case, the array is called "data["colorImages"]

But... I can't hard-code anything here because the same thing happens on eBay... for example: http://www.ebay.com/itm/Summer-Women-Casual-Chiffon-Loose-Tops-Batwing-Short-Sleeve-Loose-T-Shirt-Blouse-/351411949784?pt=LH_DefaultDomain_0&var=&hash=item51d1c8d0d8

The filenames I need here are in "enImgCarousel"

On a side note, when I use the following javascript bookmarklet for each url to get images, I'm able to get the correct images:

a='';
for (b=0;b<document.images.length;b++){
    a+='<img src='+document.images[b].src+'><br>'};
    ifa=''){
        document.writea+'</center>');
        void(document.close())
    }else{
        alert('No images!')
    }

Back to Nokogiri and XPath, I've also tried with:

tmp2.xpath("//img").each do |src|...

and

 tmp2.xpath("html//img").each do |src|

Any ideas how I should do this or which direction to go in?

回答1:

This is alternative way to solve what you would like to achieve; you can use capybara and poltergeist and I got the one you want to get. So I assume you don't have to dive into javascript with this solution.

If you scrape, I recommend that you consider capybara with poltergeist, you can find many sources to reference.

Hereafter is the code what I have tried. Hope it would help! 

require 'capybara'
require 'capybara/dsl'
require 'capybara/poltergeist'

Capybara.register_driver :poltergeist_debug do |app|
  Capybara::Poltergeist::Driver.new(app, inspector: true)
end

Capybara.javascript_driver = :poltergeist_debug
Capybara.current_driver = :poltergeist_debug 

# Amazon Case
visit_site('https://www.amazon.com/dp/B00T46V758/?tag=stackoverfl08-20')
doc_amazon = Nokogiri::HTML.parse(page.html)
doc_amazon.xpath("//img/@src").each do |src|
  p src.value  
end 

#ebay case
visit_site('https://www.ebay.com/itm/Summer-Women-Casual-Chiffon-Loose-Tops-Batwing-Short-Sleeve-Loose-T-Shirt-Blouse-/351411949784?pt=LH_DefaultDomain_0&var=&hash=item51d1c8d0d8')    
doc_ebay = Nokogiri::HTML.parse(page.html)
doc_ebay.xpath("//img/@src").each do |src|
  p src.value  
end

if you want to dig into it...(it seems you don't want)

doc.xpath("//div[@id='imgTagWrapperId']/img").attribute('src').value
# => "https://images-na.ssl-images-amazon.com/images/I/81%2BTW8762BL._UX453_.jpg"

 doc.xpath("//div[@id='mainImgHldr']/img[@id='icImg']").attribute('src').value
# => "https://i.ebayimg.com/images/g/dtAAAOSwpdpVZuU~/s-l300.jpg"


回答2:

Are you trying to generate a database of competitors items with pricing, etc.?
Are you trying to grab entire categories or individual sellers? The reason why I ask is you can get an RSS feed of items each seller lists if they have turned that feature on. This way, you do not have to waste time scraping a page when you can get the central data from an RSS feed.

When parsing webpages, depending upon where you are in the webpage (you mentioned carousel) the indices you are encountering are from the stash of thumbnails representing the larger images.
I recommend looking at the eBay API and the Amazon API and finding the RSS feeds for the sellers first.

As far as getting past any Javascript issues, the webpage loads rotating slideshows and carousels dynamically, so you will have to use Mechanize (as RAJ suggested above) or Beautiful Soup or Selenium to get fully rendered web pages in which all images are in a scrapable state.

Feel free to post your source if there is anything else I can help with.



回答3:

Sorry, as I am posting the answer from mobile phone, I can't write full code right away, however, I can give you a way. You should use Mechanize with selenium-webdriver & watir instead of only Nokogiri.

Using Mechanize, you will be able to handle elements coming from JavaScript. You can mock the actual moves on browser i.e. you can code for clicking on links/buttons, you can wait for image load and then can scrape it. And all this can be done using Mechanize very easily.



标签： ruby-on-rails ruby xpath web-scraping nokogiri
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