Image decoding device for expanding a partial image from an entire image

An image decoding device at least comprising:

• a Huffman decoding unit configured to decode encoded data including compressed image data compressed by a Huffman encoding process;
• and
• a reverse zigzag scan unit configured to convert, into a two-dimensional array of data, a one-dimensional array of data decoded by the Huffman decoding unit, wherein
• the encoded data has a structure in which a front marker group, the compressed image data, and an EOI marker defining an end of the encoded data are arranged sequentially,
• the front marker group at least includes:
• a SOI marker that defines a head of the encoded data;
• a DQT marker that defines a quantization table;
• a SOF marker that defines a size of the compressed image data;
• a DHT marker that defines a Huffman code table;
• and
• a SOS marker that defines that the compressed image data exists subsequent to the SOS marker,
• the Huffman decoding unit includes:
• a front marker analysis unit configured to analyze the encoded data sequentially received, extract each marker of the front marker group, and outputs each extracted marker to the reverse zigzag scan unit;
• a final marker analysis unit configured to analyze the encoded data sequentially received, and output an end signal to the reverse zigzag scan unit when the EOI marker is detected;
• a code analysis unit configured to analyze the compressed image data in the encoded data sequentially received, and sequentially recognize and output zero run information, group number information, and additional bit information;
• and
• a frequency conversion unit configured to sequentially generate coefficient information based on the zero run information, the group number information and the additional bit information each sequentially output from the code analysis unit, and output the coefficient information to the reverse zigzag scan unit,
• the code analysis unit is configured to receive the encoded data sequentially received and receive cutout information for cutting out a partial image from an entire image that is decodable based on the compressed image data, and
• when the cutout information is received, only in a case where the compressed image data sequentially received is compressed image data intended for cutout, the code analysis unit is configured to output, to the frequency conversion unit, the zero run information, the group number information, and the additional bit information, each of which is recognized by analyzing the compressed image data.