legal ground
Chapter IV, Article 7 of the Provisional Regulations on Marriage Registration
When registering for marriage, the parties concerned shall submit recent two-inch half-length bareheaded photos of both parties.
Article 1049 of the Civil Code
Both men and women who want to get married should apply for marriage registration in person at the marriage registration office. Those who meet the requirements of this law shall be registered and issued a marriage certificate. The marriage relationship is established when the marriage registration is completed. Those who have not registered for marriage shall re-register.