Implement mDCv chunk described in PNG 3rd Edition (Priority 2)

[digitaltvguy]

mDCv or Mastering Display Color Volume (SMPTE ST 2086) stores static metadata which idenfies display characteristics of the mastering display and allows optimized tone and color mapping to a target (consumer display).

mDCv is helpful because the content creation display may have superior capabilities compared to the target display, therefore tone and color mapping may be necessary

[svgeesus]

https://w3c.github.io/PNG-spec/#mDCv-chunk