Adding hand-crafted features to a convolutional neural network (CNN) in TensorFlow
I figured it out. If we denote the additional features as x_feat, I changed the lines from

h_pool2_flat = tf.reshape(h_pool2, [-1, 7*7*64])
h_fc1 = tf.nn.relu(tf.matmul(h_pool2_flat, W_fc1) + b_fc1)


to

h_pool2_flat = tf.reshape(h_pool2, [-1, 7*7*64])
h_pool2_flat = tf.concat( [h_pool2_flat, x_feat ], 1 )
h_fc1 = tf.nn.relu(tf.matmul(h_pool2_flat, W_fc1) + b_fc1)