Apparatus for converting floating point values to gamma corrected fixed point values
View Patent ↗Graphics processing circuitry includes processing circuitry operative to generate pixel information in response to primitive information, and a correction circuit, coupled to the processing circuitry, operative to generate gamma corrected pixel information in response to the pixel information. The correction circuit converts the floating point pixel information generated by the processing circuitry into a gamma corrected fixed-point value so that gamma space pixel data is stored in the frame buffer. This fixed point gamma corrected pixel information, converted from the floating point pixel information, compensates for the non-linear display characteristics exhibited by current display devices. This results in the display output being more accurate; thereby, improving the appearance quality of the resulting image.
1. A graphics processing circuit, comprising:
processing circuitry operative to generate floating point pixel information in response to primitive information;
a gamma correction circuit, operatively coupled to receive the floating point pixel information from the processing circuitry, and operative to generate fixed point gamma corrected pixel information in response to the floating point pixel information;
a look up table for providing base integer data and first input data based on the floating point pixel information wherein the first input data represents a difference value associated with a point on a gamma correction curve;
a multiplication circuit operatively coupled to the look up table and operative to provide first intermediate data in response to the first input data and second input data representing a mantissa portion of the floating point pixel information;
a first divider circuit, operatively coupled to the multiplication circuit, and operative to provide normalized second intermediate data in response to the first intermediate data; and
an addition circuit, operatively coupled to the first divider circuit, and operative to provide fixed point gamma corrected pixel information.
2. The graphics processing circuit of claim 1 , further including a frame buffer, operatively coupled to the gamma correction circuit, that stores the fixed point gamma corrected pixel information for display.
3. The graphics processing circuit of claim 1 , wherein the floating point pixel information is represented as 24-bit data and the fixed point gamma corrected pixel information is represented as 10-bit data.
4. A gamma correction circuit, comprising:
a multiplication circuit operative to provide first intermediate data in response to first input data representing a difference value associated with a point on a gamma correction curve and second input data representing a mantissa portion of floating point pixel information;
a first divider circuit, operatively coupled to the multiplication circuit, and operative to provide normalized second intermediate data in response to the first intermediate data;
an addition circuit, operatively coupled to the first divider circuit, and operative to provide third intermediate data in response to the normalized second intermediate data and base integer data representing a discreet value along a gamma correction curve; and
a second divider circuit, coupled to the addition circuit, and operative to provide fixed point gamma corrected pixel information in response to the third intermediate data.
5. The gamma correction circuit of claim 4 , further including a look up table for providing the base integer data and the first input data in response to a floating point pixel value.
6. The gamma correction circuit of claim 4 , further including an output buffer, coupled to the second divider, operative to provide one of: the fixed point gamma corrected data and a clipped value to a frame buffer.
7. The gamma correction circuit of claim 6 , wherein the output buffer provides the one of the fixed point gamma corrected data and the clipped value in response to a control signal.
8. The gamma correction circuit of claim 7 , wherein the output buffer includes a multiplexer.
9. A graphics processor comprising:
processing circuitry operative to generate floating point pixel information in response to primitive information; and
a gamma correction circuit, coupled to receive the floating point pixel information from the processing circuitry, and operative to generate fixed point gamma corrected pixel information in response to the floating point pixel information and further including:
a look up table for providing base integer data and first input data based on the floating point pixel information wherein the first input data represents a difference value associated with a point on a gamma correction curve;
a multiplication circuit operatively couple to the look up table and operative to provide first intermediate data in response to the first input data and second input data representing a mantissa portion of the floating point pixel information;
a first divider circuit, operatively coupled to the multiplication circuit, and operative to provide normalized second intermediate data in response to the first intermediate data;
an addition circuit, operatively coupled to the first divider circuit, and operative to provide third intermediate data in response to the normalized second intermediate data and base integer data representing a discreet value along a gamma correction curve;
a second divider circuit, coupled to the addition circuit, and operative to provide fixed point gamma corrected pixel information in response to the third intermediate data; and
an output buffer, coupled to the second divider, operative to provide one of: the fixed point gamma corrected data and a clipped value to a frame buffer.
10. The graphics processor of claim 9 , further including a frame buffer, operatively coupled to the gamma correction circuit, that stores the fixed point gamma corrected pixel information for display.
11. The graphics processor of claim 9 , wherein the floating point pixel information is represented as 24-bit data and the fixed point gamma corrected pixel information is represented as 10-bit data.
12. A graphics processing circuit, comprising:
processing circuitry operative to generate floating point pixel information in response to primitive information;
a gamma correction circuit, operatively coupled to receive the floating point pixel information from the processing circuitry, and operative to generate fixed point gamma corrected pixel information in response to the floating point pixel information, comprising;
a look up table for providing base integer data and first input data based on the floating point pixel information wherein the first input data represents a difference value associated with a point on a gamma correction curve.
a multiplication circuit operatively coupled to the look up table and operative to provide first intermediate data in response to the first input data and second input data representing a mantissa portion of the floating point pixel information;
a first divider circuit, operatively coupled to the multiplication circuit, and operative to provide normalized second intermediate data in response to the first intermediate data;
an addition circuit, operatively coupled to the first divider circuit, and operative to provide third intermediate data in response to the normalized second intermediate data and base integer data representing a discreet value along a gamma correction curve; and
a second divider circuit, coupled to the addition circuit, and operative to provide fixed point gamma corrected pixel information in response to the third intermediate data.