Adaptive spatial gamut mapping via dynamic thresholding

A system for adaptive spatial gamut mapping of a color image in an image processing system, the system comprising:

• a memory;
• a storage medium for storing data;
• and
• a processor in communication with the storage medium and the memory, the processor executing machine readable instructions for performing:
• receiving, from said memory, an input color image having a plurality of pixels;
• applying a color gamut-mapping algorithm to the input color image to produce a gamut-mapped color image;
• computing a difference between a selected channel of the input color image and the gamut-mapped color image to produce a difference image;
• computing a local measure of complexity for a current pixel in the difference image;
• using the computed local measure of complexity to obtain at least one parameter value used by a spatial bilateral filter;
• applying the spatial bilateral filter, using the obtained parameter value, to the current pixel of the difference image to produce a modified pixel in a modified difference image;
• and
• calculating a modified gamut-mapped color image from the modified difference image and the gamut-mapped color image.

A computer implemented method for adaptive spatial gamut mapping of a color image in an image processing system, the method comprising:

• receiving, from a memory, an input color image having a plurality of pixels;
• executing a color gamut-mapping algorithm to the input color image to produce a gamut-mapped color image;
• computing a difference between a selected channel of the input color image and the gamut-mapped image to produce a difference image;
• computing a local measure of complexity based on values of pixels in a neighborhood of pixels surrounding a current pixel in the difference image;
• selecting a spatial bilateral filter which only processes pixel values in a neighborhood surrounding a given pixel having a difference which is greater than a threshold value;
• retrieving a look-up table which maps the local measure of complexity to the threshold value;
• mapping the local measure of complexity through the look-up table to obtain the threshold value;
• applying the spatial bilateral filter, using the obtained threshold value, to the current pixel of the difference image to produce a modified pixel in a modified difference image;
• calculating a modified gamut-mapped color image by adding the modified difference image values and the gamut-mapped color image values at each corresponding pixel;
• and
• mapping the modified gamut-mapped color image to the device gamut and converting it to a device-dependent representation in preparation for rendering to an image output device.