Context-aware Exposure Auto-correction

Global exposure auto-correction over-exposed under-exposed low-contrast input automatic histogram stretching

Global exposure auto-correction Detection: valid histogram range < threshold Method: stretch histogram, adjust gamma curve Test Images # Global Correction Percentage 1370 63 4.6% #: Globally over-exposed, under-exposed & low-contrast images Test Images include party, family, vacation, landscape, street view, pets

Local exposure auto-correction High dynamic range scene input Auto adjustment [WLPG] Local shadow / Highlight [ours]

Local exposure auto-correction Back-lighting object input Auto adjustment [WLPG] Local shadow / Highlight [ours]

High dynamic range scene detection segment sky region scene region input extract features sky detection , , local contrast in scene region sky histogram scene histogram confidence map of sky classifier

Samples of high dynamic range scene True: False:

High dynamic range scene Test Images detected sky image Percentage 1370 316 23% True HDR scene # Percentage False HDR Scene 190 13.87% 126 #: True HDR scene images / Test Images

Back-lighting object detection The most attractive backlit object is human! extract features face detection Histogram, local contrast in face/body region input classifier Histogram of image body detection input

Samples of back-lighting object True: False:

Back-lighting object Test Images detected human image Percentage 1370 595 43.4% True backlit human # Percentage False backlit human 102 7.44% 493 #: True backlit human images / Test Images

( hdr scene 13.87% + backlit human 7.44% ) Summary Global incorrect exposure v.s. local incorrect exposure The “detected Human + Sky images” account for almost 66.5% of the whole test images Global Local 4.6% 21.31% ( hdr scene 13.87% + backlit human 7.44% )