## Description of the .ti3 format

This is an ASCII text, CGATS, Argyll specific format, used to hold device value and CIE/Spectral value pairs, the raw information needed to create device profiles. This file is typically created using the chartread, dispread, filmread, scanin, fakeread or one of the conversion tools such as cb2ti3, kodak2ti3, txt2ti3.
While fully compatible with the CGATS.5 Data Exchange Format, the particular required keywords and fields are unique to Argyll, hence an Argyll specific file identifier CTI3 is used to avoid confusion with standard ANSI or CGATS files.
The .ti3 format changes from time to time with new releases, to add new functionality, but generally retains backwards compatibility. Note that in the description below, the word "may" indicates an optional component, while the word "shall" indicates a necessary component.
Generally a .ti3 file contains only one table, the table containing the colorimetric information. The exception is for a display in which a set of RAMDAC values (most likely the result of display calibration, or simply the video LUT (RAMDAC) values present in the display when the test values were read) are recorded in a second table.
The first table contains the following:
The file identifier (First 7 characters) shall be CTI3.
A # character introduces a comment.
There may be DESCRIPTOR, ORIGINATOR, or CREATED keywords and values (as per CGATS).
There shall be a DEVICE_CLASS keyword that has a value of "OUTPUT", "DISPLAY" or "INPUT".
This indicates to the profile program what type of device the color information is from.
An "OUTPUT" type device may have a TOTAL_INK_LIMIT keyword that has a numeric value indicating the maximum sum of the device channel values as a percentage (T.A.C.), used in creating the test chart. This will be used by the profiler as a value indicating what the valid device gamut is, and what total ink limit should be used in creating the profile tables.
A "DISPLAY" type device may have a LUMINANCE_XYZ_CDM2 keyword that contains the absolute XYZ value of white in candelas per meter squared, e.g. "112.334770 119.657745 121.474236".
A display device may also have a NORMALIZED_TO_Y_100 keyword that must have a value of "NO" or "YES", to indicate whether the CIE values have been normalised so that the largest has a Y value of 100. If this is a display type device and there is no NORMALIZED_TO_Y_100 keyword, then it can be assumed that the value are normalized to Y = 100. If the values are normalized to Y = 100, then the absolute values can be restored by multiplying the XYZ values by the LUMINANCE_XYZ_CDM2 Y value and dividing by 100.
There may be a keyword TARGET_INSTRUMENT which will identify the instrument used to read the test values. This is used by the profiling program to determine the spectral characteristics of the instrument illuminant if Fluorescent Whitener Compensation is desired. The value shall be one of:
"Xrite DTP20"
"Xrite DTP22"
"Xrite DTP41"
"Xrite DTP51"
"Xrite DTP92"
"Xrite DTP94"
"GretagMacbeth Spectrolino"
"GretagMacbeth SpectroScan"
"GretagMacbeth SpectroScanT"
"Spectrocam"
"GretagMacbeth i1 Display"
"GretagMacbeth i1 Monitor"
"GretagMacbeth i1 Pro"
"X-Rite ColorMunki"
"Colorimtre HCFR"
"ColorVision Spyder2"
"Datacolor Spyder3"
"GretagMacbeth Huey"
All instruments except the Spectrocam are assumed to have an "A" type illuminant (incandescent lamp of 2850 degrees Kelvin.)
There may be a INSTRUMENT_TYPE_SPECTRAL keyword that must have a value of "NO" or "YES", to indicate whether the instrument is based on spectral measurement or not.
There may be keywords with associated values SINGLE_DIM_STEPS, COMP_GREY_STEPS, MULTI_DIM_STEPS or FULL_SPREAD_PATCHES, that document the composition of the test chart patches.
There shall be a keyword COLOR_REP that has a value that indicates what colorspaces the test values connect. The colorspaces shall be encoded with one or two letters per component, and the two color spaces shall then separated by an _ (underscore) character. For output and display devices, the device space shall come first, followed by the PCS space. For an input device, the PCS shall come first, followed by the device space. The PCS space shall be either XYZ space, indicated by XYZ, or D50 while point L*a*b* space, indicated by LAB. The device spaces shall use the following letter encoding:
Cyan C
Magenta M
Yellow Y
Black K
Orange O
Red R
Green G
Blue B
White W
Light Cyan c
Light Magenta m
Light Yellow y
Light Black k
Medium Cyan 2c
Medium Magenta 2m
Medium Yellow 2y
Medium Black 2k
Light Light Black 1k
There may be an a previx i preceeding the device space letter encoding, indicating that although the space appears to be an additive space, it is in fact a subtractive device.
Typical values might be: "RGB_XYZ" or "RGB_LAB" for an RGB display, "iRGB_XYZ" or "iRGB_LAB" for an RGB printer, "CMYK_XYZ" for a printer, "XYZ_RGB" for an RGB scanner.
If spectral values are going to be included in the file, the following keywords and values shall be used:
SPECTRAL_BANDS shall contain the number of spectral bands in the readings, e.g. "36".
SPECTRAL_START_NM shall contain the wavelength in nanometers of the first band, e.g. "380.0".
SPECTRAL_END_NM shall contain the wavelength in nanometers of the last band, e.g. "730.0".
The NUMBER_OF_FIELDS keyword shall have a value that indicates the number of fields in each data set, e.g. 43 (as per CGATS).
The start of the declaration of the fields shall be marked by the BEGIN_DATA_FORMAT keyword (as per CGATS).
Then shall follow the names of the fields. Standard CGATS field names such as:
SAMPLE_ID, RGB_R, RGB_G, RGB_B, CMYK_C, CMYK_M, CMYK_Y, CMYK_K, XYZ_X, XYZ_Y, XYZ_Z, LAB_L, LAB_A or LAB_B
shall be used where appropriate. Other device fields shall use the appropriate pattern, e.g. CMYKOG_G etc. Spectral band values shall be named SPEC_XXX, where XXX is the nearest integer values of the number of nanometers of the band.
Optional patch location information shall use the SAMPLE_LOC field and shall be of quoted string type.
The definition of the fields shall be terminated by the END_DATA_FORMAT keyword (as per CGATS).
The NUMBER_OF_SETS keyword shall have a value that indicates the number of sets of data, e.g. 1000 (as per CGATS).
The start of the values of the data sets shall be marked by the BEGIN_DATA keyword (as per CGATS).
Each set of data shall be on one line, and shall be separated by white space. All device values shall be percentages (e.g. values from 0.0 to 100.0). XYZ values shall normalized to a Y value of 100.0. L*a*b* values will have their normal range (L* 0.0 to 100.0, a* and b* typically -128.0 to 128.0).
The end of the values of the data sets shall be marked by the END_DATA keyword (as per CGATS).
Generally any other keywords and values will be ignored.
If a second table is present, and it is a display RAMDAC calibration, printers or input devices per channel calibration curves, and will be of the CAL file format..