Luminance changing image processing with color constancy

A method of operating an image color processing apparatus, comprising:

• applying by a first circuit, respective weighted or non-weighted functions to each of the red, green and blue color components of an input image resulting in modified red, green and blue color components, wherein each of the functions is one of:
• (i) a non-linear function;
• (ii) a linear scaling function multiplying a component (B) of the input color by a weight;
• and (iii) the unity function of an input component or combinations of the input components, wherein at least one modified component represents one of the red, green and blue color components of the input image weighted by a non-unity real-numbered value;
• calculating by a second circuit, a maximum of at least the three modified components;
• applying, by a third circuit, a function to the maximum yielding an output value, wherein the function is predetermined having a constraint that the output value for the highest value of the maximum cannot be higher than 1.0;
• calculating, by a fourth circuit, a scaling parameter being equal to the output value divided by the maximum;
• and
• multiplying, using a fifth circuit, the red, green and blue color components of the input color by the scaling parameter, yielding one or more color components of an output color.

A non-transitory computer-readable storage-medium storing computer instructions which, when executed by a processor, configure the processor to perform a method of operating an image color processing apparatus, the method comprising:

• applying by a first circuit, respective weighted or non-weighted functions to each of the red, green and blue color components of an input image resulting in modified red, green and blue color components, wherein each of the functions is one of:
• (i) a non-linear function;
• (ii) a linear scaling function multiplying a component (B) of the input color by a weight;
• and (iii) the unity function of an input component or combinations of the input components, wherein at least one modified component represents one of the red, green and blue color components of the input image weighted by a non-unity real-numbered value;
• calculating by a second circuit, a maximum of at least the three modified components;
• applying, by a third circuit, a function to the maximum yielding an output value, wherein the function is predetermined having a constraint that the output value for the highest value of the maximum cannot be higher than 1.0;
• calculating, by a fourth circuit, a scaling parameter being equal to the output value divided by the maximum;
• and
• multiplying, using a fifth circuit, the red, green and blue color components of the input color by the scaling parameter, yielding one or more color components of an output color.