RPA Robotic Process Automation – Display PDF in Browser and Select Area Using PDF.js – Javascript and PDF.js v1.x

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code.js

      
// PDF file to display:
var url = 'https://cdn.mozilla.net/pdfjs/tracemonkey.pdf';
// Note: if absolute URL from the remote server is provided, 
// you should configure the CORS header on your server.

// The workerSrc property should be specified
PDFJS.workerSrc = 'https://cdnjs.cloudflare.com/ajax/libs/pdf.js/1.10.97/pdf.worker.js';

var pdfDoc = null,
  pageNum = 1,
  pageRendering = false,
  pageNumPending = null,
  scale = 1,
  canvas = document.getElementById('the-canvas'),
  ctx = canvas.getContext('2d');

/**
 * Get page info from document, resize canvas accordingly, and render page.
 * @param num Page number.
 */
function renderPage(num) {
  pageRendering = true;
  // Using promise to fetch the page
  pdfDoc.getPage(num).then(function (page) {
    var viewport = page.getViewport(scale);
    canvas.height = viewport.height;
    canvas.width = viewport.width;

    // Render PDF page into canvas context
    var renderContext = {
      canvasContext: ctx,
      viewport: viewport
    };
    var renderTask = page.render(renderContext);

    // Wait until the end of the rendering
    renderTask.promise.then(function () {
      pageRendering = false;
      if (pageNumPending !== null) {
        // New page rendering is pending
        renderPage(pageNumPending);
        pageNumPending = null;
      }
    });
  });

  // Update page counters
  document.getElementById('page_num').textContent = num;
}

/**
 * If another page rendering in progress, wait until it finished; 
 * otherwise, execute the rendering immediately.
 */
function queueRenderPage(num) {
  if (pageRendering) {
    pageNumPending = num;
  } else {
    renderPage(num);
  }
}

/**
 * Displays previous page.
 */
function onPrevPage() {
  if (pageNum <= 1) {
    return;
  }
  pageNum--;
  displayCoordinates();
  queueRenderPage(pageNum);
}
document.getElementById('prev').addEventListener('click', onPrevPage);

/**
 * Displays next page.
 */
function onNextPage() {
  if (pageNum >= pdfDoc.numPages) {
    return;
  }
  pageNum++;
  displayCoordinates();
  queueRenderPage(pageNum);
}
document.getElementById('next').addEventListener('click', onNextPage);

/**
 * Download PDF asynchronously.
 */
PDFJS.getDocument(url).then(function (pdfDoc_) {
  pdfDoc = pdfDoc_;
  document.getElementById('page_count').textContent = pdfDoc.numPages;

  // Initial/first page rendering
  renderPage(pageNum);
});


// Area selector
var startX,
  startY,
  selectedBoxes = [],
  $selectionMarquee = $('#selectionMarquee'),
  clearSelectedAreasBtn = $('#clearSelectedAreasBtn'),
  wrapper = $("#canvas-wrap"),
  wrapperObj = wrapper[0],
  $allCords = $('#all-cords'),
  positionBox = function ($box, coordinates) {
    $box.css(
      'top', coordinates.top + wrapperObj.offsetTop
    ).css(
      'left', coordinates.left + wrapperObj.offsetLeft
      ).css(
      'height', coordinates.bottom - coordinates.top
      ).css(
      'width', coordinates.right - coordinates.left
      ).css(
      'border', 'solid grey 1px'
      );
  },

  compareNumbers = function (a, b) {
    return a - b;
  },

  getBoxCoordinates = function (startX, startY, endX, endY) {
    var x = [startX, endX].sort(compareNumbers),
      y = [startY, endY].sort(compareNumbers);

    return {
      top: y[0],
      left: x[0],
      right: x[1],
      bottom: y[1]
    };
  },

  trackMouse = function (event) {
    var position = getBoxCoordinates(startX, startY, event.pageX - wrapperObj.offsetLeft, event.pageY - wrapperObj.offsetTop);
    console.log(position);
    positionBox($selectionMarquee, position);
  },

  displayCoordinates = function () {
    var msg = 'Areas:\n';
    if (!selectedBoxes.length) {
      $allCords.html('');
      return;
    }
    selectedBoxes.forEach(function (box) {
      msg += '<li>(' + box.left + ', ' + box.top + ') - (' + (box.right) + ', ' + (box.bottom) + ')</li>';
    });
    $allCords.html(msg);
  },
  
  endMoving = function (event) {
    var position,
      $selectedBox;

    $selectionMarquee.hide();

    position = getBoxCoordinates(startX, startY, event.pageX - wrapperObj.offsetLeft, event.pageY - wrapperObj.offsetTop);

    if (position.left !== position.right && position.top !== position.bottom) {
      $selectedBox = $('<div class="selected-box selected-box-item"></div>');
      $selectedBox.hide();
      wrapper.append($selectedBox);

      positionBox($selectedBox, position, wrapper[0]);

      $selectedBox.show();

      selectedBoxes.push(position);
      displayCoordinates();

      wrapper.off('mousemove', trackMouse);
      $selectionMarquee.off('mousemove', trackMouse);
      $selectionMarquee.off('mouseup', endMoving);
    }
  };

wrapper.on('mousedown', function (event) {
  event.preventDefault();
  startX = event.pageX - wrapperObj.offsetLeft;
  startY = event.pageY - wrapperObj.offsetTop;
  positionBox($selectionMarquee, getBoxCoordinates(startX, startY, startX, startY), this);
  $selectionMarquee.show();

  wrapper.on('mousemove', trackMouse);
  $selectionMarquee.on('mousemove', trackMouse);
  $selectionMarquee.on('mouseup', endMoving);
}).on('mouseup', endMoving);

clearSelectedAreasBtn.on('click', function(event){
  selectedBoxes = [];
  $('.selected-box-item').remove();
  displayCoordinates();
});
    

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