The invention relates to a process for the linearization and characterization of an image producing RGB or CMYK device according to the preamble of the independent claim.
The invention relates to the field of graphic processing and especially to the image producing devices used in its workflows, especially printers.
The typical graphic processing workflow includes the use of different image producing devices and offers the user the possibility to produce, look at, correct and output, especially print, images. The workflow normally extends from an image capturing step with input devices such as digital cameras and scanners to an observation step with display devices such as, for example a monitor, to an output step with output devices such as, for example, a printer. The user thereby aims in the output step for images which either come as close as possible to the underlying original or which are (according to individual conceptions) perceived as “nice” or “pleasing”.
Because of the technological differences between the image producing devices (for example CCD, Filter, Inkjet, others), the need exists to first adjust the devices involved to a common colour description language. One of the most important points is thereby the linearization and characterization of each image producing device involved.
The linearization is most of the time carried out by the device manufacturer, requires special knowledge and requires a lot of time. The ICC (International Colour Committee) has defined what is to be understood under characterization: an ICC colour profile is assigned to each image producing device which describes the colour capabilities/limitations of the device.
The generation of an ICC profile for an image producing device is a relatively lengthy process which includes amongst other things the reproduction (for example printing) of a colour test chart with a respective device as well as the colorimetric evaluation of the many hundred individual test fields on the reproduced colour test chart. Standard colour test charts set by the ICC are often used, but special colour test charts of the manufacturers of profile generation software are also used. Common colour test charts are, for example, the IT8.73 (928 measurement fields) and the ECI2002 (1440 measurement fields). The working with such large colour test charts is very time consuming and costly for the normal (for example private) user.