Multidimensional image retargeting! Tone Mapping Rafał Mantiuk Bangor University, UK Research Institute of Visual Computing http://www.bangor.ac.uk/mantiuk/ 1 Outline •  What is tone-mapping? •  Arithmetic of HDR images •  The perception of HDR scenes •  Major approaches to tone-mapping •  Illumination & reflectance separation •  Forward visual model •  Forward & inverse visual model •  Constraint mapping problem 3 Outline •  What is tone-mapping? •  Arithmetic of HDR images •  The perception of HDR scenes •  Major approaches to tone-mapping •  Illumination & reflectance separation •  Forward visual model •  Forward & inverse visual model •  Constraint mapping problem 4 Tone-mapping problem luminance range [cd/m2] human vision simultaneously adapted Tone mapping conventional display 6 Question •  Who has never used a tone-mapping operator? Each camera needs to tone-map a real-world captured light before it can be stored as a JPEG. This is essentially the same process as tone- mapping, although knows as ‘color reproduction’ or ‘color processing’. 7 Three intents of tone-mapping 1.  Scene reproduction operator 2.  Visual system simulator 3.  Best subjective quality 8 Intent #1: Scene reproduction problem Real-world 9 Display Goal: map colors to a restricted color space 9 Intent #2: Visual system simulator The eye adapted to the display viewing conditions Real-world The eye adapted to the real-world viewing 11 conditions Display Goal: match color appearance 11 Visual system simulator - example •  Simulation of glare 12 Intent #3: Best subjective quality •  Tools •  Photoshop •  Lightroom •  Photomatix •  Techniques •  Color-grading •  Often artistic intent 13