ASTC interpolation

A method of using a binary logic circuit to perform an interpolation calculation between two endpoint values E0 and E1 using a weighting index i for generating an interpolated result P, the values E0 and E1 being formed from Adaptive Scalable Texture Compression (ASTC) colour endpoint values C0 and C1 respectively, the colour endpoint values C0 and C1 being low-dynamic range (LDR) or high dynamic range (HDR) values, the method comprising:

• performing at an interpolation unit of the binary logic circuit an interpolation between the colour endpoint values C0 and C1 using the weighting index i to generate a first intermediate interpolated result C2;
• receiving at combination logic circuitry of the binary logic circuit the first intermediate interpolated result C2;
• determining whether the colour endpoint values are LDR values or HDR values;
• in response to determining that the colour endpoint values are LDR values, outputting the interpolated result P calculated using one or more logical processing operations according to the equation:
• (1) P=└((C2«8)+C2+32)/64┘ when the interpolated result is not to be compatible with an sRGB colour space;
• (2) P=└((C2«8)+128.64+32)/64┘ when the interpolated result is to be compatible with an sRGB colour space;
• and
• in response to determining that the colour endpoint values are HDR values, outputting the interpolated result P calculated using one or more logical processing operations according to the equation:
• (3) P=(C2+2)»2.

A non-transitory computer readable storage medium having stored thereon a computer readable description of a binary logic circuit for performing an interpolation calculation between two endpoint values E0 and E1 using a weighting index i for generating an interpolated result P, the values E0 and E1 being formed from Adaptive Scalable Texture Compression (ASTC) colour endpoint values C0 and C1 respectively, the colour endpoint values C0 and C1 being low-dynamic range (LDR) or high dynamic range (HDR) values, the circuit comprising:

• an interpolation unit configured to perform an interpolation between the colour endpoint values C0 and C1 using the weighting index i to generate a first intermediate interpolated result C2;
• combinational logic circuitry configured to:
• receive the first intermediate interpolated result C2;
• determine whether the colour endpoint values are LDR values or HDR values;
• in response to determining that the colour endpoint values are LDR values, output the interpolated result P calculated using one or more logical processing operations according to the equation:
• (1) P=└((C2«8)+C2+32)/64┘ when the interpolated result is not to be compatible with an sRGB colour space;
• (2) P=└((C2«8)+128.64+32)/64┘ when the interpolated result is to be compatible with an sRGB colour space;
• and
• in response to determining that the colour endpoint values are HDR values, output the interpolated result P calculated using one or more logical processing operations according to the equation (3) P=(C2+2)»2.