Status Updates From Fake Photos (The MIT Press ...
Fake Photos (The MIT Press Essential Knowledge series) by
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André
is on page 207 of 232
Double Compression:
・re-save→annomalies in the distrib. of a DCT value
Interpolation=patterns
・ColorFilterArray on top of cam-sensor transmits only part of visible spectrum to each cell (cell detects intensity not color); Bayer pattern;
⅔ of all RGB values interpol'd
・resized parts
Stable noise:
・id individual cam
・PhotoResponseNonUniformity PRNU: some cells over/under-report, estimate from 15 hi-res images
CGI:
…
— Oct 22, 2019 07:30PM
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・re-save→annomalies in the distrib. of a DCT value
Interpolation=patterns
・ColorFilterArray on top of cam-sensor transmits only part of visible spectrum to each cell (cell detects intensity not color); Bayer pattern;
⅔ of all RGB values interpol'd
・resized parts
Stable noise:
・id individual cam
・PhotoResponseNonUniformity PRNU: some cells over/under-report, estimate from 15 hi-res images
CGI:
…
André
is on page 141 of 232
Camera/Tool fingerprinting:
- JPEG quantization table
- JPEG file-intern thumbnail variability
- JPEG data segments vary (segment markers):
iPhone: SOI APP1 SOI DQT DQT SOF0 …
Photoshop: SOI APP1 SOI APP13 APP14 …
JPEG ghosts
Detect cloning in image:
- naive→combinatorial explosion
- Harris HOG & RANSAC (openCV)
3D Face/Scene Reconstruction:
- plausible shadows, bodily postures etc
- tools: FaceGen, MakeHuman
— Oct 20, 2019 04:43PM
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- JPEG quantization table
- JPEG file-intern thumbnail variability
- JPEG data segments vary (segment markers):
iPhone: SOI APP1 SOI DQT DQT SOF0 …
Photoshop: SOI APP1 SOI APP13 APP14 …
JPEG ghosts
Detect cloning in image:
- naive→combinatorial explosion
- Harris HOG & RANSAC (openCV)
3D Face/Scene Reconstruction:
- plausible shadows, bodily postures etc
- tools: FaceGen, MakeHuman
André
is on page 81 of 232
Line analyses:
- implausible # of light sources or vanishing points (∩ of van. lines)
- shadows: http://americanscientist.org/sites/am...
- inconsistent reflections
- lensflare source
- real img only 1 principal point (orthocenter of selectd parallel lines)
- area uniformity: enhance small diffs in brightn.→levels filter
- remov perspective distortion→more info
— Oct 20, 2019 11:53AM
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- implausible # of light sources or vanishing points (∩ of van. lines)
- shadows: http://americanscientist.org/sites/am...
- inconsistent reflections
- lensflare source
- real img only 1 principal point (orthocenter of selectd parallel lines)
- area uniformity: enhance small diffs in brightn.→levels filter
- remov perspective distortion→more info
André
is on page 46 of 232
- inconsistencies betw image metadata & scene:
high ISO→img noise
"f-number, shutter speed, and ISO and converted them to APEX […] The sum […] meaning that the scene brightness was 3 corresponding to a dimly lit room. This didn't make sense"
- distance betw eye pupils (IPD) fairly constant among people:
"Using the assumed IPD of 6.5 cm […] I was able to determine that the geometry of the scene was not plausible"
— Oct 19, 2019 08:14PM
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high ISO→img noise
"f-number, shutter speed, and ISO and converted them to APEX […] The sum […] meaning that the scene brightness was 3 corresponding to a dimly lit room. This didn't make sense"
- distance betw eye pupils (IPD) fairly constant among people:
"Using the assumed IPD of 6.5 cm […] I was able to determine that the geometry of the scene was not plausible"
