code: public void concatCTM(float a, float b, float c, float d, float e, float f) {
          content.append(a).append(' ').append(b).append(' ').append(c).append(' ');
          content.append(d).append(' ').append(e).append(' ').append(f).append(" cm").append_i(separator);
      }
docs: Concatenate a matrix to the current transformation matrix.
  @param a an element of the transformation matrix
  @param b an element of the transformation matrix
  @param c an element of the transformation matrix
  @param d an element of the transformation matrix
  @param e an element of the transformation matrix
  @param f an element of the transformation matrix