Display-optimized hdr video contrast adaptation

Abstract

To obtain in a pragmatic manner better watchable images for various potentially considerably different viewing environment light levels, the inventor proposes an apparatus (900) for processing an input image which has pixels which have input luminances which fall within a first luminance dynamic range (DR_1), which first luminance dynamic range has a first maximum luminance (PL V HIDR), the apparatus comprising: image input (921) arranged to obtain the input image (513); a data input (920) for receiving a reference luminance mapping function (F_L) which is metadata associated with the input image, which specifies how luminances are to be re-graded between two reference images, wherein the output image has an output maximum luminance (PL V MDR) which is different from the first maximum luminance; the apparatus further comprising a user value circuit (903) arranged to determine and output a user correction value (UCBVal) as set by a human user of the apparatus; and a maximum luminance determination unit (901) arranged to: obtain the user correction value (UCBVal) from the user value circuit (903); and output an adjusted maximum luminance value (PL V CO) as the result of subtracting user correction value (UCBVal) from the output maximum luminance (PL V MDR); the apparatus further comprising a display adaptation circuit (510) arranged to determine an adapted luminance mapping function (FL DA) based on the adjusted maximum luminance value (PL V CO), and the reference luminance mapping function (F_L), wherein the calculation of the adapted luminance mapping function (FL DA) involves finding a position (pos) on a metric (SM) which corresponds to the adjusted maximum luminance value (PL V CO), wherein a first endpoint of the metric corresponds to the first maximum luminance (PL V HDR) and a second endpoint of the metric corresponds to a maximum luminance of the second reference image, wherein the first endpoint of the metric is collocated, for any normalized input luma (Yn CCO), on a point on a diagonal which has it horizontal and vertical coordinate equal to the normalized input luma, wherein the second endpoint is located on the locus of the reference luminance mapping function (F_L), wherein the display adaptation unit is arranged to apply the adapted luminance mapping function (FL_DA) to input luminances or input lumas coding the input luminances to obtain output luminances or output lumas, and to output these output lumas or output luminances as pixel colors of the output image.

Dependencies are inferred from the claim text.