Abstract: A method of manipulating a train of electrical signals equal in binary terms to the density gradation levels of a plurality of image pixels of an original image over a range of density gradation levels for controlling the reproduction of the original image on a receiving sheet in a thermal printer having an array of controllable printing elements corresponding in number to the pixels in an image line and an actuating circuit for actuating the respective printing elements in individually accessible fashion. In the method, the electrical signals for a given line of the image pixels are stored in a line memory and are outputted one by one from the line memory to a non-zero detector and downcounter for identification as to zero or non-zero status and downcounting of all non-zero signals to reduce the level thereof by one level.

Abstract: Processes for increasing the density of images obtained by thermal dye sublimation transfer and printer for performing these processes.In addition to a dye transfer step, the same portion of a dye donor element is at least one more time image-wise heated and a second dye image which is in register with said first dye image is transferred to said receiving element.Alternatively, to a dye transfer step at least one step is added in which another portion of the dye donor element is image-wise heated and the image is transferred not in register with the image transferred during the first step.