Abstract: A method of selectively assigning to a picture element to be imaged with a color reproduction system a pertinent (permanent) indication relating to the distinguishing of color with respect to picture element, wherein, on the basis of the associated parameter values related to color saturation and intensity, a choice is first made for that picture element from a permanent indication of colorlessness a permanent indication of color behavior, and a provisional indication concerning an undefined color behavior. In the case of a picture element having a provisional indication, this indication is then converted to a permanent indication on the basis of the results of an analysis of the distribution of parameter values in the color space with respect to picture elements occurring within an environment of the associated picture element. According to this method, pastel hues can be reproduced in a logical and perceptually acceptable manner despite the presence of scanner noise.

Abstract: A method and system of determining a reference value for the intensity associated with a color indication variable and obtained by scanning an original with a color scanning unit the color scanning unit being adapted to scan the original point-by-point, the method comprising determining a locally valid reference value for each scanned point and for each color indication variable, provided the intensity value related thereto deviates from a defined standard value by less than a preset value, by adapting the then locally available reference value by using a fraction of the value representing the intensity in the case of the color indication variable concerned. For example, a white reference value (white point) can be determined for an original point by point, with the result that weak color tones which are perceived as white are also regarded as white, while in addition small variations in these weak color tones (e.g. uneven yellowing) are also noted as white.

Abstract: A method and apparatus for forming a multi-color image in which colored toner powder is used to form color separation images in the secondary colors magenta, cyan and yellow and also in one of the primary colors red, green or blue, such that of the color separation images formed in the secondary colors, there is formed, with transparent toner powder, at least as many color separation images so that the two primary colors not formed as separate separation images, are represented therein, affording the possibility of forming multi-color images by means of combinations of transparent and non-transparent toner powders, the method being performed by combining on an intermediate support those separation images formed with toner powder not required to be transparent and then transferring them to an image receiving material and subsequently transferring in registration to the image receiving material those separation images which are required to be formed with transparent toner powder.

Abstract: A method of forming a multi-color image, comprising image elements in a first color which along at least part of their circumference adjoin image elements of one or more following colors wherein separation images in the first, second, third and any following color are each built up from image dot patterns of colored toner powder. The separation images are transferred to an intermediate support to collect said separate images to form a multi-color image. The multi-color image is then transferred from the intermediate support to an image receiving material. The second and each following generated separation image is generated so that the image elements, which on transfer onto the intermediate support are required to adjoin image elements of a separation image already transferred thereto previously, at least partially overlap said previously transferred image elements.