lutappendix.txt

4. LUT Appendix
======================
4.1 - 1D LUT file format:
	4.1.1 Format
	LUT_1D_SIZE 1024
	LUT_1D_BITS 16
	LUT_1D_NAME lut_information
	r0 g0 b0
	r1 g1 b1
	...
	...
	...
	r1023 g1023 b1023

	NOTE:
	LUT_1D_SIZE: should be 1024 when inbit is 10 in LUT attribute info and should be 4096 when inbit is 12

	4.1.2 File name suffix : .lut
	
	4.1.3 DIT 1DLUT name
		dit[ID].lut
		ID:
		01
		02
		...
		15
		16

	4.1.4 Calibration 1DLUT name:
	user[ID].lut
	ID: 1, 2 or 3
	
4.2 - 3D LUT file format:
	4.2.1 cube file format:
	Same as Adobe's cube lut specification, without TITLE, DOMAIN_MIN, DOMAIN_MAX keywords.
	only use LUT_3D_SIZE keyword to specify lut size, LUT_3D_SIZE must be 17, 33 or 65

	4.2.2 dat file format:
	<FileHeader> + <FileData>
	
	4.2.2.1 file header(128Bytes)
	struct FileHeader {
		unsigned long magic; // 4Bytes, must be 0x42340299(little endian)
		unsigned long ver; // 4Bytes, 0x02000001(little endian)
		char model[16]; // 16Bytes, monitor model, e.g. "LM-2461W", "CM170". NOTE: model string must match target monitor's model
		char version[16]; // 16Bytes, data version, "x.y.zz". eg. "1.0.11"
		unsigned long data_checksum; // 4Bytes, FileData sum(little endian)
		unsigned long length; // 4Bytes, data length = 1048576 (little endian)
		char description[16]; // 16Bytes, 3dlut description info, eg. "CalSoftware"
		unsigned long reserved2; // 4Bytes, reserved
		char name[16]; // 16Bytes, information of lut
		char reserved[42]; // 43 Bytes, reserved
		uint8_t size; // 17 for 17x17x17
		unsigned char header_checksum; // file header sum
	};

	4.2.2.2 file data
	data size:
	<node number> x <bytes per node>

	node number:
	17x17x17 when size is 17 in 3DLUT attribute info
	33x33x33 when size is 33 in 3DLUT attribute info bytes per node:
	4 bytes when outbit is 10 in 3DLUT attribute info data structure:
	32Bit = red_value | (green_value << 10) | (blue_value << 20)
	8 bytes when outbit is 12 in 3DLUT attribute info
	64Bit = red_value | (green_value << 16) | (blue_value << 32)

	data endian: big endian
	green index blue index
	value range:
	  red_value - [0, 1023] when outbit is 10, [0 - 4095] when outbit is 12
	  green_value - [0, 1023] when outbit is 10, [0 - 4095] when outbit is 12
	  blue_value - [0, 1023] when outbit is 10, [0 - 4095] when outbit is 12
	
	data layout:
	red index green index blue index
	0 		  0			  0
	1 		  0			  0
	2		  0			  0
	.		  .			  .
	.		  .			  .
	. 		  .			  .
	16		  0			  0
	0		  1			  0
	1 		  1			  0
	1 		  2			  1
	.		  .			  .
	.		  .			  .
	. 		  .			  .
	16 		  16		  16

	4.2.2.3 FileData sum calculation
	unsigned int data_sum = 0;
	unsigned char buf[19652];
	read(fd, buf, 19652);
	for (int i = 0; i < 19652; i++)
	data_sum += (unsigned int)buf[i];

	4.2.2.4 file header sum calculation
	unsigned char header_sum = 0;
	unsigned char buf[128]; memcpy(buf, fileheader, 128); for (int i = 0; i < 128; i++)
	header_sum += buf[i];

	4.2.3 3DLUT File naming rule
	Calibration 3DLUT name:
	[color space].{dat,cfe}
	  color space:
		rec709
		smptec
		ebu
		dcip3
		user1
		user2
		user3

	DIT 3DLUT name:
	dit[ID].{dat,cfe}
	  ID:
		01
		02
		...
		15
		16

	4.3 - CSC data structure
	
	4.3.1 CSC data size: 18 x 4 Bytes
	
	4.3.2 CSC data layout
		Gain[0][0]
		Gain[0][1]
		Gain[0][2]
		Gain[1][0]
		Gain[1][1]
		Gain[1][2]
		Gain[2][0]
		Gain[2][1]
		Gain[2][2]
		Offset[0]
		Offset[1]
		Offset[2]
		Min[0]
		Min[1]
		Min[2]
		Max[0]
		Max[1]
		Max[2]