dist/jspdf.node.debug.js
function writeImageToPDF(x, y, w, h, info, index, images, rotation) {
    var dims = determineWidthAndHeight.call(this, w, h, info),
        coord = this.internal.getCoordinateString,
        vcoord = this.internal.getVerticalCoordinateString;
    w = dims[0];
    h = dims[1];
    images[index] = info;

    if (rotation) {
      rotation *= Math.PI / 180;
      var c = Math.cos(rotation);
      var s = Math.sin(rotation); //like in pdf Reference do it 4 digits instead of 2

      var f4 = function f4(number) {
        return number.toFixed(4);
      };

      var rotationTransformationMatrix = [f4(c), f4(s), f4(s * -1), f4(c), 0, 0, 'cm'];
    }

    this.internal.write('q'); //Save graphics state

    if (rotation) {
      this.internal.write([1, '0', '0', 1, coord(x), vcoord(y + h), 'cm'].join(' ')); //Translate

      this.internal.write(rotationTransformationMatrix.join(' ')); //Rotate

      this.internal.write([coord(w), '0', '0', coord(h), '0', '0', 'cm'].join(' ')); //Scale
    } else {
      this.internal.write([coord(w), '0', '0', coord(h), coord(x), vcoord(y + h), 'cm'].join(' ')); //Translate and Scale
    }

    this.internal.write('/I' + info['i'] + ' Do'); //Paint Image

    this.internal.write('Q'); //Restore graphics state
  }
function writeImageToPDF(x, y, w, h, info, index, images, rotation) {
    var dims = determineWidthAndHeight.call(this, w, h, info),
        coord = this.internal.getCoordinateString,
        vcoord = this.internal.getVerticalCoordinateString;
    w = dims[0];
    h = dims[1];
    images[index] = info;

    if (rotation) {
      rotation *= Math.PI / 180;
      var c = Math.cos(rotation);
      var s = Math.sin(rotation); //like in pdf Reference do it 4 digits instead of 2

      var f4 = function f4(number) {
        return number.toFixed(4);
      };

      var rotationTransformationMatrix = [f4(c), f4(s), f4(s * -1), f4(c), 0, 0, 'cm'];
    }

    this.internal.write('q'); //Save graphics state

    if (rotation) {
      this.internal.write([1, '0', '0', 1, coord(x), vcoord(y + h), 'cm'].join(' ')); //Translate

      this.internal.write(rotationTransformationMatrix.join(' ')); //Rotate

      this.internal.write([coord(w), '0', '0', coord(h), '0', '0', 'cm'].join(' ')); //Scale
    } else {
      this.internal.write([coord(w), '0', '0', coord(h), coord(x), vcoord(y + h), 'cm'].join(' ')); //Translate and Scale
    }

    this.internal.write('/I' + info['i'] + ' Do'); //Paint Image

    this.internal.write('Q'); //Restore graphics state
  }
Image functionality ported from pdf.js