Method of separating a foreground picture signal from a mixed picture signal, using gamma correction, and arrangement for performing said method

Claim 5

A method as claimed in claim 1, characterized in that KC(f) is chosen in dependence upon the value k of the control signal.

Claim 6

A method as claimed in claim 1, characterized in that KC(f) is defined as an exponential curve extending in the C b /C r color plane.

Claim 7

An arrangement for for separating a foreground picture signal FG from a mixed picture signal MG having a key color KC and transition colors to the key color in key regions, said arrangement comprising an input for receiving the mixed picture signal MG; means coupled to said input for generating a control signal k in dependence on color locations of pixels of the mixed picture signal MG; a first multiplier having a first input for receiving said control signal k and a second input for receiving a background signal BG; means for generating a value KC(f) in dependence on a value of the control signal k; a second multiplier having a first input for receiving the control signal k and a second input for receiving a value -KC(f) based on the value KC(f); a first adder having a first input coupled to an output of said second multiplier and a second input coupled to the input of said arrangement; and a second adder having a first input coupled to an output of said first multiplier and a second input coupled to an output of said first adder, an output of said second adder carrying the foreground signal FG separated from the mixed picture signal MG in accordance with the relationship FG=MG-k*KC(f)+k*BG, where KC(f) is determined in dependence upon color intensity as far as an angle of KC(f) in a C b /C r color plane is concerned, characterized in that the values of KC(f) are stored in a table contained in a memory addressed by the control signal k, and in that for separating the foreground picture signal FG from the mixed picture signal MG, the corresponding values of KC(f) are read from the memory and used in a vectorial subtraction performed in the first adder.

Claim 8

An arrangement for for separating a foreground picture signal FG from a mixed picture signal MG having a key color KC and transition colors to the key color in key regions, said arrangement comprising an input for receiving the mixed picture signal MG; means coupled to said input for generating a control signal k in dependence on color locations of pixels of the mixed picture signal MG; a first multiplier having a first input for receiving said control signal k and a second input for receiving a background signal BG; means for generating a value KC(f) in dependence on a value of the control signal k; a second multiplier having a first input for receiving the control signal k and a second input for receiving a value -KC(f) based on the value KC(f); a first adder having a first input coupled to an output of said second multiplier and a second input coupled to the input of said arrangement; and a second adder having a first input coupled to an output of said first multiplier and a second input coupled to an output of said first adder, an output of said second adder carrying the foreground signal FG separated from the mixed picture signal MG in accordance with the relationship FG=MG-k*KC(f)+k*BG, where KC(f) is determined in dependence upon color intensity as far as an angle of KC(f) in a C b /C r color plane is concerned, characterized in that the values of KC(f) are stored in a table contained in a memory addressed by the control signal k, and in that for separating the foreground picture signal FG from the mixed picture signal MG, the corresponding values of KC(f) are read from the memory and used in a vectorial subtraction performed in the first adder.

Claim 9

A method as claimed in claim 2, characterized in that KC(f) is chosen in dependence upon the value k of the control signal.

Claim 10

A method as claimed in claim 2, characterized in that KC(f) is defined as an exponential curve extending in a C b /C r color plane.

Claim 11

A method as claimed in claim 3, characterized in that KC(f) is defined as an exponential curve extending in the C b /C r color plane.

Claim 12

A method as claimed in claim 6, characterized in that KC(f) is defined as an exponential curve extending in a C b /C r color plane.

Claim 13

An arrangement for for separating a foreground picture signal FG from a mixed picture signal MG having a key color KC and transition colors to the key color in key regions, said arrangement comprising an input for receiving the mixed picture signal MG; means coupled to said input for generating a control signal k in dependence on color locations of pixels of the mixed picture signal MG; a first multiplier having a first input for receiving said control signal k and a second input for receiving a background signal BG; means for generating a value KC(f) in dependence on a value of the control signal k; a second multiplier having a first input for receiving the control signal k and a second input for receiving a value -KC(f) based on the value KC(f); a first adder having a first input coupled to an output of said second multiplier and a second input coupled to the input of said arrangement; and a second adder having a first input coupled to an output of said first multiplier and a second input coupled to an output of said first adder, an output of said second adder carrying the foreground signal FG separated from the mixed picture signal MG in accordance with the relationship FG=MG-k*KC(f)+k*BG, where KC(f) is determined in dependence upon color intensity as far as three color components Y, C r , C b of KC(f) are concerned, characterized in that the values of KC(f) are stored in a table contained in a memory addressed by the control signal K, and in that for separating the foreground picture signal FG from the mixed picture signal MG, the corresponding values of KC(f) are read from the memory and used in a vectorial subtraction performed by the first adder.

Claim 14

An arrangement for for separating a foreground picture signal FG from a mixed picture signal MG having a key color KC and transition colors to the key color in key regions, said arrangement comprising an input for receiving the mixed picture signal MG; means coupled to said input for generating a control signal k in dependence on color locations of pixels of the mixed picture signal MG; a first multiplier having a first input for receiving said control signal k and a second input for receiving a background signal BG; means for generating a value KC(f) in dependence on a value of the control signal k; a second multiplier having a first input for receiving the control signal k and a second input for receiving a value -KC(f) based on the value KC(f); a first adder having a first input coupled to an output of said second multiplier and a second input coupled to the input of said arrangement; and a second adder having a first input coupled to an output of said first multiplier and a second input coupled to an output of said first adder, an output of said second adder carrying the foreground signal FG separated from the mixed picture signal MG in accordance with the relationship FG=MG-k*KC(f)+k*BG, where KC(f) is determined in dependence upon color intensity as far as three color components Y, C r , C b of KC(f) are concerned, characterized in that the values of KC(f) are stored in a table contained in a memory addressed by the control signal K, and in that for separating the foreground picture signal FG from the mixed picture signal MG, the corresponding values of KC(f) are read from the memory and used in a vectorial subtraction performed by the first adder.

Claim 15

An arrangement as claimed in claim 5, characterized in that KC(f) is defined as an exponential curve extending in the C b /C r color plane.

Claim 16

An arrangement as claimed in claim 10, characterized in that KC(f) is defined as an exponential curve extending in a C b /C r color plane.