Amendment 3 to Recommendation ITU-T T.88 | ISO/IEC 14492 is the first amendment to introduce colour extension into JBIG2. There are many ideas and possibilities to incorporate colour information on JBIG2. In this amendment, as the first step of introducing coloured information, the following principles are adopted.
In order to show the text region segment with colour support, a flag to show colour supporting the text region segment and a flag to show its colour space (e.g., sRGB) are defined. Colour information is attached to the end of the text region segment as colour section, and ITU-T T.45 representation is used to code colour change information to keep the decodability by the current decoder. A total of 32 colours are defined by default in this amendment. An additional colour dictionary can be defined using ITU-T T.45-like expression in the colour palette segment. In the generic region segment, if background colour is needed to be defined, another intermediate region segment which has the colour as foreground should be placed under the segment. The order of the priority in the layout is newly defined.