A LUT (lot) of image filters on Android

on YouTube ↗33m

" summary

Implementation uses RenderScript on Android to apply 3D LUTs for image filters, converting designer LUTs (HALD/horizontal strip) into a RenderScript Allocation. Uses 64x64x64 LUT (~262k colors) stored as a strip, and discovers RenderScript intrinsic 3DLUT fails on alpha, so a custom RenderScript is implemented that trilinear interpolation and un-premultiply alpha during lookup. Transparent tests expose array out‑of‑bounds crashes fixed by clamping. Resulting pipeline produces correct filters with reduced banding but only moderate performance; further optimization of interpolation and RenderScript remains.

AI-written summary · about

" chapters (10)

1. 0:00Introduction and background
2. 1:55Different filter approaches
3. 7:12What is a 3D lookup table
4. 10:45RenderScript for LUT processing
5. 16:18Custom RenderScript script
6. 21:10Pre-multiplied alpha issue
7. 24:22Banding and interpolation
8. 27:35Debugging RenderScript crashes
9. 29:19Handling LUT formats
10. 31:05Conclusion and references

" related talks

• 36mA LUT (lot) of image filters on AndroidGarima Jain · droidcon Italy 2020
• 35mPractical Image Processing in AndroidRebecca Franks · DevFest Ukraine 2018
• 36mThe Evolution of Android Graphics in Android 12/13Dan Galpin · droidcon San Francisco 2022
• 21mSimple and Fast Image Processing with RenderScriptQuentin Menini · Android Makers 2018
• 40mHigh Performance Applications with RenderScriptJason Sams, Tim Murray · Google I/O 2013
• 40mThe Evolution of Android GraphicsDan Galpin · droidcon New York 2022
• 16mAndroid GraphicsChet Haase, Sumir Kataria · Android Dev Summit 2022
• 39mHella-Parallel Compute with RenderScriptLydia Schiff · droidcon San Francisco 2017