Ancient Handwritten Characters Database (CASIA-AHCDB) is designed for character recognition research. The database contains more than 2.2 million annotated character samples of 10,658 classes. The character samples come from more than 12,000 pages of annotated Chinese ancient handwritten documents. According to different sources of documents, the database is mainly divided into two sub-databases: Complete Library in Four Sections (style1) and Ancient Buddhist Scriptures (style2). Each sub-database can be divided into three parts based on its applications: basic category set, enhanced category set and reserved category set. The basic category sets of style1 and style2 have the same 2,365 classes, and the enhanced category sets of style1 and style2 have no intersecting classes. For reserved category set, training and testing set are not divided due to the few samples.

Style1 contains 25 books, numbered “book_01” to “book_25”. Among them, (book_01, book_02) were written by one person, so did (book_03, book_04), (book_05, book_06) and (book_07, book_08) , the rest are written by different people. We make books 01-20 as training set and books 21-25 as testing set.

Style2 contains Buddhist scriptures documents from 10 different periods. The writer of each volume is no longer verifiable. The 001 volumes of Buddhist scriptures in the 01 period are numbered “period_01/volume_001”. We make Buddhist scriptures from period 09-10 as training set and Buddhist scriptures from period 01-08 as testing set.

Table I. Structure and Statistic of CASIA-AHCDB

Database Structure				Classes	Characters
CASIA AHCDB	Style1	Basic Category	Train	2,365	832,939
			Test	2,365	254,162
		Enhanced Category	Train	3,227	89,204
			Test	3,227	36,258
		Reserved Category		3,819	19,763
	Style2	Basic Category	Train	2,365	728,423
			Test	2,365	204,547
		Enhanced Category	Train	783	71,179
			Test	783	19,597
		Reserved Category		2,450	8,213
Summation				12,229	2,264,285