This document outlines as much of the Scitex CT (CH) file format as I have been able to reverse engineer. It works for all the files I have tried it on, but you probably have different files than I have.

The scitex ct file format is a common file format used in the prepress industry. Ct files will almost always contain either a CMYK or a greyscale image.

Common extentions are .ch .ct and .sct

“ct” most likely stands for Continuous Tone.

NOTE: All numbers are stored in the big endian byte order

Offset Length Description
0×0 80 bytes Comment string padded with spaces
0×50 2 bytes Text “CT”. This appears to be a marker identifying the file format as scitex CT. If you don’t have this in your file, you don’t have a scitex CT file.
0×400 1 byte Units of measurement (0=MM,1=INCH)
0×401 1 byte Number of Channels
0×402 2 bytes Color Model (7=RGB, 8=GREYSCALE, 15=CMYK)
0×404 14 bytes Height in Units stored as a Scitex FP
0×412 14 bytes Width in Units stored as a Scitex FP
0×420 12 bytes Height in pixels.
Stored as 12 digits of text including sign (”%+012d”).
0×42C 12 bytes Width in pixels.
Stored as 12 digits of text including sign (”%+012d”).
0×800 (W*H*C) bytes Image Pixels stored in row interleaved format.
An extra byte is added to each channel in each row when the pixel width is odd.

The spaces from 0×52 to 0×399 and from 0×43A to 0×799 may safely be written out as zeroes

The Scitex Floating Point number format

The Scitex FP format is a textual representation of a floating point
number expressed in a very specific form of scientific notation.
This format is not necesarly the default formating of your *printf
functions.

+.e
This works out to exactly 14 characters.

Good examples


  • +.34232332e+03
  • +.93283898e-01

Bad examples

  • +0.3423233e+03
  • +3.4232332e+02
  • +.342323329e+3
  • +.342323329e03
  • .342323329e+03

Download an example ct file

  • test_rgb.ct.

     Channels: 3
 Color Space: RGB
 Size (mm)
    Width:  37.499997
    Height: 24.999998
 Size (pixels)
    Width:  150
    Height: 100
 Resolution (pixels/mm)
    Width:  4.00000032000003
    Height: 4.00000032000003

If you have any information on the scitex lw (linework), nct (new ct), or nlw (new lw) file formats, please pass it along

If you have any questions or comments about this document email me at jaycox@electricmessiah.org