Gamma correction circuit approximating non-linear digital conversion
AssigneeCanon Kabushiki Kaisha
InventorsKosuke Nobuoka, Tsutomu Fukatsu
Life of this patent
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Abstract
A gamma correction circuit for converting N-bit input data into M-bit output data by using a gamma correction curve approximated by a polygonal line having a plurality of straight line sections each having a different slope, the gamma correction circuit including a calculation circuit for executing conversion calculation for each the straight line section; and a control circuit for controlling the calculation circuit in accordance with a value of the input data so that the calculation circuit executes the conversion calculation for each the straight line section corresponding to the value.
Claims9
A gamma correction circuit for converting N-bit digital input data into M-bit output data by using a gamma correction curve approximated by a polygonal line having a plurality of straight line sections each having a different slope, said gamma correction circuit comprising:
- calculation means for executing a conversion calculation for each said straight line section, said calculation means including a plurality of channels of calculation circuits for performing the conversion calculations, one channel for each said straight line section, and each said calculation circuit including at least a constant-multiple circuit, an adder, a subtracter, and storage means for storing addition data and subtraction data obtained by said adder and said subtracter;
- and
- control means for controlling said calculation means in accordance with a value of said input data so that said calculation means executes said conversion calculation for each said straight line section corresponding to said input data value, said control means including gate means for selecting and outputting one of the outputs of said plurality of calculation circuits in accordance with the value of said input data.
A non-linear conversion circuit, comprising:
- (a) input means for inputting an N-bit digital signal;
- (b) a plurality of conversion means for converting the input digital signal using a predetermined conversion characteristic, each of said plurality of conversion means including at least a constant-multiple circuit, an adder, a subtracter, and storage means for storing addition data and subtraction data obtained by said adder and said subtracter;
- and
- (c) selection means for selecting a plurality of output signals of said plurality of conversion means, according to an input level of the digital signal.
A signal conversion apparatus comprising:
- input means for inputting a digital signal;
- conversion means for converting the input digital signal by performing an operation using the input digital signal and a predetermined coefficient, and for outputting the converted signal, said conversion means including at least a constant-multiple circuit, an adder for providing addition data, a subtracter for providing subtraction data, and storage means for storing the addition data and subtraction data provided by said adder and said subtracter, respectively;
- memory means for storing predetermined data relating to said predetermined coefficient;
- and
- setting means for setting predetermined data stored in said memory means into said conversion means in accordance with a characteristic of the input digital signal.
Dependencies are inferred from the claim text.