Post on 27-Mar-2015
Context-aware Exposure Auto-correction
Context-aware Exposure Auto-correction
Global exposure auto-correctionGlobal exposure auto-correction
over-exposed
under-exposed
low-contrast
input automatic histogram stretching
Global exposure auto-correctionGlobal 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-correctionLocal exposure auto-correction
input Local shadow / Highlight [ours]
• High dynamic range scene
Auto adjustment[WLPG]
Local exposure auto-correctionLocal exposure auto-correction
input Local shadow / Highlight [ours]
• Back-lighting object
Auto adjustment[WLPG]
High dynamic range scene detectionHigh dynamic range scene detection
input
confidence map of sky
sky detection
sky region scene region
segment
sky histogram scene histogram
local contrastin scene region
extract features
classifier
, ,
Samples of high dynamic range sceneSamples of high dynamic range scene
• True: • False:
High dynamic range sceneHigh dynamic range scene
True HDR scene # Percentage False HDR Scene
190 13.87% 126
#: True HDR scene images / Test Images
Test Images detected sky image Percentage
1370 316 23%
Back-lighting object detectionBack-lighting object detection
input
face detection
body detection
input
extract features
classifier
Histogram, local contrastin face/body
region
Histogram of image
• The most attractive backlit object is human!
Samples of back-lighting objectSamples of back-lighting object
• True: • False:
Back-lighting objectBack-lighting object
True backlit human # Percentage False backlit human
102 7.44% 493
#: True backlit human images / Test Images
Test Images
detected human image Percentage
1370 595 43.4%
SummarySummary
• 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% )