Efficient image processing on content-adaptive PQ signal domain

A method of merging images, comprising:

• by apparatus comprising one or more data processors configured by software, one or more programmable logic devices, one or more logic circuits or a combination thereof:
• obtaining a first and a second forward reshaping function for re-quantizing a first and second pre-reshaped image into a first and second reshaped image respectively, wherein each forward reshaping function is obtained by:
• generating a noise mask image comprising a masking noise estimate for each pixel in a corresponding pre-reshaped image;
• generating a noise mask histogram comprising a number of bins, wherein for each bin, pixels in the first and the second pre-reshaped image are identified which have pixel values in a range associated with said bin, and a minimum pixel value of the noise mask image pixels corresponding to the identified pixels is selected as a bin value for said bin;
• determining a minimal bit depth for each bin of the noise mask histogram based on the bin value of said bin;
• and
• computing the first and the second forward reshaping function on the basis of the determined minimal bit depths;
• obtaining a first and a second backward reshaping function for reversing operation of the first and the second forward reshaping function respectively;
• generating a further forward reshaping function from noise measurements of the first and the second pre-reshaped image by:
• generating a noise masking histogram comprising a number of bins, each bin value corresponding to a minimum of bin values of the number of bins of the noise mask histogram used for generating the first and the second forward reshaping function respectively;
• computing an estimate of a minimum number of bits required for each bin of the noise mask histogram based on the value of said bin;
• and
• computing the further forward reshaping function on a basis of the estimate of the minimum number of bits;
• deriving, based on the further forward reshaping function and the first backward reshaping function, a first combined reshaping function;
• deriving, based on the further forward reshaping function and the second backward reshaping function, a second combined reshaping function;
• mapping, based on the first combined reshaping function, the first reshaped image into a first mapped image;
• mapping, based on the second combined reshaping function, the second reshaped image into a second mapped image;
• and
• combining the first mapped image and the second mapped image into a combined image, the combined image comprising a plurality of merged or blended pixel values, thereby reducing a computational intensity of obtaining the combined image.