Pinterest Image Downloader: drop into developer console on Pinterest page and run 'download_pins("<search string>")', where <search string> is a placeholder for an optional pin title filter. The script will pull all the pin images fitting the search filter using jQuery, zip using JSZip and offer download using FileSaver.js.

pinterest_downloader.js

//Pinterest Image Downloader

//USAGE: 
//drop script into developer console on Pinterest page
//enter download_pins("<search string>")
//where <search string> is a placeholder for an optional pin title filter.

//The script will pull all the pin images fitting the search filter using jQuery, 
//zip them all using JSZip and offer download using FileSaver.js.

download_pins = function(search_string) {
    var main = function($){
        console.log('Fetching Pins...')

        //settings:
        var TITLE_FILTER = search_string;
        var MAX_PINS = 1000;
        var SCROLL_THRESHOLD = 1;
        var TIMEOUT_STEP = 2000;

        //globals
        var zip = new JSZip();
        var zipfilecount = 0;
        var pincount = 0;

        //functions:
        var funcs = {};
        funcs.scrollToBottom = function(){
              var pins = funcs.getPinDivs();
              bottom = document.body.scrollHeight;
              current = window.innerHeight+ document.documentElement.scrollTop + SCROLL_THRESHOLD;
              if((bottom-current) > 0 && pins.length < MAX_PINS){
                window.scrollTo(0, bottom);
                setTimeout(funcs.scrollToBottom, TIMEOUT_STEP);
              }
              else{
                funcs.readPins();
              }
        };
        funcs.getContainer = function(){
          return $('div.mainContainer');
        }
        funcs.getPinDivs = function(){
          return funcs.getContainer().find('div[data-grid-item]');
        };
        funcs.readPins = function(){
          funcs.getPinDivs().each(function(){
            var pinurl = $(this).find('[href]').attr('href');
            var pintitle = $(this).find('div.pinWrapper span span').first().text();
            //debugger;
            if(pintitle.match(TITLE_FILTER) && pinurl.match(/^\/pin\//)){
              pincount++;
              funcs.savePinImage(pinurl);
            }
            if(pincount >= MAX_PINS){
              return false;
            }
          });
        }
        funcs.savePinImage = function(pinurl){
          $.get(pinurl, function( data ) {
            var pinpage = $(data.module.html);
              pinpage.find('div.closeupCenterImage img[src]').each(function(){
                var imgurl = $(this).attr('src');
                if(imgurl.match(/i\.pinimg\.com\/564x/)){
                  funcs.saveImage(imgurl);
                  return false;
                }
              });
          });
        }
        funcs.saveImage = function(url){
          var filename = url.substr(url.lastIndexOf('/') + 1);
          console.log(url);
          funcs.convertFileToDataURLviaFileReader(url, function(data){
            data = data.substr(data.lastIndexOf(',') + 1);
            zip.file(filename, data, {base64 : true});
            zipfilecount++;

            if(pincount == zipfilecount){
              funcs.saveZip();
            }
          });
        }
        funcs.convertFileToDataURLviaFileReader =function(url, callback) {
          var xhr = new XMLHttpRequest();
          xhr.onload = function() {
            var reader = new FileReader();
            reader.onloadend = function() {
              callback(reader.result);
            }
            reader.readAsDataURL(xhr.response);
          };
          xhr.open('GET', url);
          xhr.responseType = 'blob';
          xhr.send();
        }
        funcs.saveZip = function(){
          console.log(zipfilecount + " Pins found.");
          console.log("Zipping and downloading ...");
          zip.generateAsync({type:"blob"}).then(function (blob) { // 1) generate the zip file
              saveAs(blob, "pins.zip");                          // 2) trigger the download
          });
        }

        funcs.scrollToBottom();
    }

    //Script injection
    var s = ['//code.jquery.com/jquery-latest.min.js', '//cdnjs.cloudflare.com/ajax/libs/jszip/3.1.5/jszip.min.js', '//fastcdn.org/FileSaver.js/1.1.20151003/FileSaver.min.js']
    var scriptsloaded = 0;

    for(var i = 0; i<s.length; i++){
      var e = document.createElement('script');
      e.src = s[i];
      e.i = i
      e.onload = function() {
          scriptsloaded++;
          console.log(this.src + ' injected');

          if(scriptsloaded == s.length){
            main(jQuery);
          }
      };
      document.head.appendChild(e);
    }

};