Image Filtering

1
Image Filtering

• Comparison of ISP HW
• vs
• Almalence SW filters
• Tasks sharing between ISP
• And
• Almalence Imaging Libraries

2
Features chart
ISP HW Almalence SW
Multishot-compatible No Yes
Lens shading taken into account Rarely Yes
Easily configurable No Yes
3
Typical ISP pipeline
RAW
Sensor
ADC
Chroma sub- sample
RGB to YUV
Gamma correct
Sharpen
JPEG enc
Denoise
Color- space convert
Optical clamp
Scale
Black level sub
Faulty Pixel correct
Lens shading correct
Red-tinted blocks are filters
De- bayer
Culling Binning
4
ISP function with Super-Resolution

• SR utilizes image data preserved due to absence
  of filters
• SR replaces the filters with better ones

SR processing
Align
Denoise
JPEG enc
De- ghost
Enhance edges
Fuse
SR processing includesDenoise and Sharpening.
Standard filters should be turned off to preserve
image data needed for SR
5
Real life comparison

• Example images below have been taken with Galaxy
  Nexus
• Stock firmware
• Jelly Bean Android

6
Noise filter HW ISP
Lens shading correction not taken into account
Center
Corner noise outbursts
7
Noise filter Almalence
Lens shading taken in account
Center
Corner
8
Noise filter Almalence
Easily configured (API accessible from
application layer)
No filtering
Little filtering
High filtering
9
Noise filter Almalence
SW flexibility allows for more complex algorithms
Filtered with HW Some noise remaining, Some
details lost
Filtered with Almalence NF Complete removal of
noise Details remain
10
Sharpening filter HW ISP
Downscaled full image looks good
Close look oversharpening evident (halos)
11
Sharpening filter Almalence
Close look edges are enhanced, no halos
12
Super-resolution compatibility
SR result with pre-filtered images lossof
details, over-sharpen exaggerated
SR result with post-filtering