A method of tone reproduction curves computation by means of gradation trajectories in the form of Bézier curves

Tone reproduction curves (TRCs) have long been the basis for color adjustment in printing systems. Moreover, new algorithms for their processing and calculation, including tone value increase (TVI)‐based ones, are being constantly proposed. However, due to the fact that TRCs are just one‐dimensional curves covering only one colorant, they are not able to produce an exact match of all colors. Color adjustment with the help of the TRC is unstable, that is, a slight change in one color channel has a dramatic effect on the color reproduction in output. The use of gradation trajectories (GT) as an analytical model within the CIE Lab color space describing the behavior of the entire color gamut of the reproduction device makes it possible to more accurately adjust the individual color channel. Describing GT using the parametric Bézier curves further simplifies this process. In this work, we use GT to fit the TRC/TVI with the parameters recommended by ISO 12647‐2:2013.