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  • Showing only topics in ~tildes with the tag "youtube". Back to normal view / Search all groups
    1. Tildes User Script: Youtube Thumbnails Below Topic Title

      A screenshot. Following is a user script that embeds a thumbnail into the topic header. Was supposed to be trivial, but walking around the CSRP was not that easy. Luckily, someone had written a...

      A screenshot.

      Following is a user script that embeds a thumbnail into the topic header. Was supposed to be trivial, but walking around the CSRP was not that easy. Luckily, someone had written a nice useful custom Base64 encoder, because I spent more than an hour trying to get btoa to do the thing.

      // ==UserScript==
      // @name     tildesYoutubeThumbs
      // @version  1
      // @grant    GM.xmlHttpRequest
      // @namespace   tildes.net
      // @include     https://tildes.net/~*/*
      // ==/UserScript==
      
      let youtubeIcon = document.querySelector('div.topic-icon-youtube_com')
      
      if(youtubeIcon !== null) {
        let youtubeLink = youtubeIcon.nextSibling.nextSibling.href;
        let youtubeID = new URL(youtubeLink).searchParams.get('v');
        let thumbnailUrl = "https://img.youtube.com/vi/" + youtubeID + "/0.jpg";
      
        GM.xmlHttpRequest({
          method: "GET",
          url: thumbnailUrl,
          overrideMimeType: 'text/plain; charset=x-user-defined',
          onload: function(response) {
            if(response.status === 200) {
              let thumbElement = document.createElement('img');
              let thumbParentDiv = document.createElement('div');
              let header = document.querySelector('article.topic-full > header');
              let data = "data:image/jpeg;base64," + customBase64Encode(response.responseText);
              thumbElement.src = data;
              thumbElement.style = 'width: 60%; margin: auto';
              thumbElement.id = 'gk-youtube-thumbnail';
              thumbParentDiv.style = 'width: 100%; text-align:center;';
              header.appendChild(thumbParentDiv);
              thumbParentDiv.appendChild(thumbElement);
            }
          }
        });
      }
      
      // https://stackoverflow.com/questions/8778863/downloading-an-image-using-xmlhttprequest-in-a-userscript/8781262#8781262
      function customBase64Encode (inputStr) {
          var
              bbLen               = 3,
              enCharLen           = 4,
              inpLen              = inputStr.length,
              inx                 = 0,
              jnx,
              keyStr              = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
                                  + "0123456789+/=",
              output              = "",
              paddingBytes        = 0;
          var
              bytebuffer          = new Array (bbLen),
              encodedCharIndexes  = new Array (enCharLen);
      
          while (inx < inpLen) {
              for (jnx = 0;  jnx < bbLen;  ++jnx) {
                  /*--- Throw away high-order byte, as documented at:
                    https://developer.mozilla.org/En/Using_XMLHttpRequest#Handling_binary_data
                  */
                  if (inx < inpLen)
                      bytebuffer[jnx] = inputStr.charCodeAt (inx++) & 0xff;
                  else
                      bytebuffer[jnx] = 0;
              }
      
              /*--- Get each encoded character, 6 bits at a time.
                  index 0: first  6 bits
                  index 1: second 6 bits
                              (2 least significant bits from inputStr byte 1
                               + 4 most significant bits from byte 2)
                  index 2: third  6 bits
                              (4 least significant bits from inputStr byte 2
                               + 2 most significant bits from byte 3)
                  index 3: forth  6 bits (6 least significant bits from inputStr byte 3)
              */
              encodedCharIndexes[0] = bytebuffer[0] >> 2;
              encodedCharIndexes[1] = ( (bytebuffer[0] & 0x3) << 4)   |  (bytebuffer[1] >> 4);
              encodedCharIndexes[2] = ( (bytebuffer[1] & 0x0f) << 2)  |  (bytebuffer[2] >> 6);
              encodedCharIndexes[3] = bytebuffer[2] & 0x3f;
      
              //--- Determine whether padding happened, and adjust accordingly.
              paddingBytes          = inx - (inpLen - 1);
              switch (paddingBytes) {
                  case 1:
                      // Set last character to padding char
                      encodedCharIndexes[3] = 64;
                      break;
                  case 2:
                      // Set last 2 characters to padding char
                      encodedCharIndexes[3] = 64;
                      encodedCharIndexes[2] = 64;
                      break;
                  default:
                      break; // No padding - proceed
              }
      
              /*--- Now grab each appropriate character out of our keystring,
                  based on our index array and append it to the output string.
              */
              for (jnx = 0;  jnx < enCharLen;  ++jnx)
                  output += keyStr.charAt ( encodedCharIndexes[jnx] );
          }
          return output;
      }
      
      15 votes