Method of and arrangement for deriving a control signal for inserting a background signal into parts of a foreground signal

Claim 3

A method as claimed in claim 1, characterized in that the method comprises checking the homogeneity criterion both for determining the color locations of pixels of a foreground color within the region of the key color for which the control signal assumes the first value, and for determining the color locations of pixels of a foreground color different from the key color for which the control signal assumes the second value.

Claim 6

An arrangement for deriving a control signal for inserting a background signal into parts of a foreground signal, these parts being fixed by a key color, in which the control signal assumes a first value when the foreground signal represents a color in the region of the key color and a second value when the foreground signal represents a different color, and in which the control signal has a transition range between the two values, characterized in that the arrangement comprises: a memory for storing chrominance signals of the foreground signal; a digital signal processor for selecting the chrominance signals of an adjustable frame, the chrominance signals selected by the digital signal processor being read from the memory; a first and a second test circuit to which the chrominance signals read from the memory are applied via a gate circuit; a multiplexer having a first input to which an output of said second test circuit is applied, and output from the digital signal processor being applied to a second input of the multiplexer; and a write/read memory having address inputs to which an output from the multiplexer is applied; the digital signal processor being connected to the first and second test circuits, to data inputs/outputs of the write/read memory and to the multiplexer, wherein the first test circuit computes the distances between color locations of pixels of the foreground signal and a color location of the key color, for distinguishing color locations of pixels associated with foreground colors or with the key color from color locations of pixels to be associated with the transition range, and wherein the second test circuit associates those color locations of pixels whose distance to the key color's color location differs from a distance of a color location of one or a plurality of adjacent pixels to the key color's color location by more than a predetermined distance (not complying with a homogeneity criterion) with the transition range, whereby said arrangement computes intermediate values of the control signal for the color locations in the transition range, the control signal being available at an output of the write/read memory.

Claim 7

An arrangement for deriving a control signal for inserting a background signal into parts of a foreground signal, these parts being fixed by a key color, in which the control signal assumes a first value when the foreground signal represents a color in the region of the key color and a second value when the foreground signal represents a different color, and in which the control signal has a transition range between the two values, characterized in that the arrangement comprises: a memory for storing chrominance signals of the foreground signal; a digital signal processor for selecting the chrominance signals of an adjustable frame, the chrominance signals selected by the digital signal processor being read from the memory; a first and a second test circuit to which the chrominance signals read from the memory are applied via a gate circuit; a multiplexer having a first input to which an output of said second test circuit is applied, and output from the digital signal processor being applied to a second input of the multiplexer; and a write/read memory having address inputs to which an output from the multiplexer is applied; the digital signal processor being connected to the first and second test circuits, to data inputs/outputs of the write/read memory and to the multiplexer, wherein the first test circuit computes the distances between color locations of pixels of the foreground signal and a color location of the key color, for distinguishing color locations of pixels associated with foreground colors or with the key color from color locations of pixels to be associated with the transition range, and wherein the second test circuit associates those color locations of pixels whose distance to the key color's color location differs from a distance of a color location of one or a plurality of adjacent pixels to the key color's color location by more than a predetermined distance (not complying with a homogeneity criterion) with the transition range, whereby said arrangement computes intermediate values of the control signal for the color locations in the transition range, the control signal being available at an output of the write/read memory.