Building Camera Features in a Snap

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SNAP SNAP SNAP Matt Precious Building Camera Features in a SNAP

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Adding a Camera Feature to your App

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How much work do you want to do?

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How much work do you want to do? Hours Months

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Hours Months Camera Intent

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Camera Intent Hours Months

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Camera Intent Hours Months • Easy

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Camera Intent Hours Months • Easy • No control over UI

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Camera Intent Hours Months • Easy • No control over UI • No control over hardware

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Hours Months

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Use a Library Hours Months

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Use a Library Hours Months

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Library Hours Months

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Library Hours Months • A lot of code is written for you

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Library Hours Months • A lot of code is written for you • Changes and ﬁxes require understanding all the code

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github.com/Fotoapparat/Fotoapparat github.com/google/cameraview github.com/afollestad/material-camera

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Hours Months

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Hours Months DIY

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Hours Months DIY

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Hours Months DIY

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Hours Months DIY • Full control over everything

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Hours Months DIY • Full control over everything • You need to write everything

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Cameras.

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Cameras. How do they work?

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Color Formats

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http://bit.ly/2jF7Ths

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RGB

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Red Green Blue

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Red Green Blue

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Red Green Blue

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RGBA

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RGB + Alpha

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RGB A

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YUV

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YUV

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Y'CbCr

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Y' Cb Cr

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Y' Cb Cr Luma (Brightness)

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Y' Cb Cr Chrominance (Color)

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Y' Cb Cr

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Y' Cb Cr

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Y' Cb Cr

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Y' Cb Cr

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Y' Cb Cr

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Why YUV?

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RGB

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RGB 888

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RGB 888 Red Green Blue 8 bits 8 bits 8 bits

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RGB 888 Red Green Blue 24 bits per pixel 8 bits 8 bits 8 bits

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RGB 888 Red Green Blue 24 bits per pixel 8 bits 8 bits 8 bits 1920×1080 ≈ 6MB

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RGB 888 Red Green Blue 24 bits per pixel 8 bits 8 bits 8 bits 1920×1080 ≈ 6MB 60fps: 360MB/s

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RGB 888

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RGB 444

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RGB 444 Red Green Blue 4 bits 4 bits 4 bits

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RGB 444 Red Green Blue 12 bits per pixel 4 bits 4 bits 4 bits

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RGB 444 Red Green Blue 12 bits per pixel 4 bits 4 bits 4 bits 1920×1080 ≈ 3MB

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RGB 444 Red Green Blue 12 bits per pixel 4 bits 4 bits 4 bits 1920×1080 ≈ 3MB 60fps: 180MB/s

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RGB 444

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RGB 565

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RGB 565 16 bits per pixel

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RGB 565 Red Green Blue 16 bits per pixel 5 bits 5 bits 5 bits

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RGB 565 Red Green Blue 16 bits per pixel 5 bits 6 bits 5 bits

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CIE 1931

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CIE 1931

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YUV

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YUV 4:4:4

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YUV 4:4:4

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YUV 4:4:4

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YUV 4:4:4

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YUV 4:4:4 Y' Cr Cb 8 bits 8 bits 8 bits

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YUV 4:4:4 Y' Cr Cb 24 bits per pixel 8 bits 8 bits 8 bits

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YUV 4:4:4 Y' Cr Cb 24 bits per pixel 8 bits 8 bits 8 bits 1920×1080 ≈ 6MB

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YUV 4:4:4 4:4

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YUV 4:4:4 2:2

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YUV 4:2:2

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YUV 4:2:2

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YUV 4:2:2

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YUV 4:2:2

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YUV 4:2:2 Y' Cr Cb 8 bits 8 bits 8 bits 2 pixels 2 pixels

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YUV 4:2:2 Y' Cr Cb 8 bits 4 bits 4 bits

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YUV 4:2:2 Y' Cr Cb 16 bits per pixel 8 bits 4 bits 4 bits

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YUV 4:2:2 Y' Cr Cb 16 bits per pixel 8 bits 4 bits 4 bits 1920×1080 ≈ 4MB

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YUV 4:2:2 2

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YUV 4:2:2 0

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YUV 4:2:0

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YUV 4:2:0

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YUV 4:2:0

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YUV 4:2:0

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YUV 4:2:0

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YUV 4:2:0 Y' Cr Cb 8 bits 8 bits 8 bits 4 pixels 4 pixels

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YUV 4:2:0 Y' Cr Cb 8 bits 2 bits 2 bits

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YUV 4:2:0 Y' Cr Cb 12 bits per pixel 8 bits 2 bits 2 bits

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YUV 4:2:0 Y' Cr Cb 12 bits per pixel 8 bits 2 bits 2 bits 1920×1068 ≈ 3MB

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Why YUV?

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http://bit.ly/2fwAxwF

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Implementing Camera APIs

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Camera1

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Camera1 Camera2

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Camera1 Camera2 Min SDK 1 Min SDK 21 2009 2014

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Camera1 Camera2 Min SDK 1 Min SDK 21 2009 2014 100% of devices 80%* of devices

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Camera1 Camera2 Min SDK 1 Min SDK 21 2009 2014 100% of devices 80%* of devices

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Camera2

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http://bit.ly/2ylAfAs

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Permission?

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Permission? Y

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Permission? Y What cameras do you have?

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Permission? Y What cameras do you have? 1, 2

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Y What cameras do you have? 1, 2

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Tell me more about camera 1 Y What cameras do you have? 1, 2

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Tell me more about camera 1 Y What cameras do you have? 1, 2

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Tell me more about camera 1 1, 2

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Tell me more about camera 2 Tell me more about camera 1 1, 2

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Tell me more about camera 2 Tell me more about camera 1 1, 2

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Tell me more about camera 2

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Open camera 2, please Tell me more about camera 2

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Open camera 2, please OK Tell me more about camera 2

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Open camera 2, please OK

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Start capturing, please Open camera 2, please OK

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Start capturing, please xOKx Open camera 2, please OK

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Start capturing, please xOKx OK

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Start capturing, please xOKx OK

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Start capturing, please xOKx OK

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xOKx

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Capture xOKx

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Capture Capture xOKx

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Capture Capture xOKx

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github.com/Fotoapparat/Fotoapparat github.com/google/cameraview github.com/afollestad/material-camera github.com/googlesamples/android-Camera2Basic

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Strides

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Strides width: 3 height: 3 1 2 3 4 5 6 7 8 9

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Strides width: 3 height: 3 1 2 3 4 5 6 7 8 9

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Strides width: 3 height: 3 row stride 1 2 3 4 5 6 7 8 9

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Strides width: 3 height: 3 row stride: 3 1 2 3 4 5 6 7 8 9

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Strides width: 3 height: 3 row stride: 5 1 2 3 4 5 6 7 8 9

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Strides width: 3 height: 3 row stride: 5 1 2 3 4 5 6 7 8 9

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Strides width: 3 height: 3 row stride: 5 pixel stride 1 2 3 4 5 6 7 8 9

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Strides width: 3 height: 3 row stride: 5 pixel stride: 1 1 2 3 4 5 6 7 8 9

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Strides width: 3 height: 3 row stride: 5 pixel stride: 2 1 2 3 4 5 6 7 8 9

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Strides width: 3 height: 3 row stride: 5 pixel stride: 2 1 2 3 4 5 6 7 8 9

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Strides width: 3 height: 3 row stride: 7 pixel stride: 2 1 2 3 4 5 6 7 8 9

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Strides width: 3 height: 3 row stride: 7 pixel stride: 2 1 2 3 4 5 6 7 8 9

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Kernels

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Edge Detection

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Edge Detection 0 1 0 1 –4 1 0 1 0

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Convolution

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Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 0 255 255 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Convolution

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Convolution 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 1 0 1 –4 1 0 1 0 Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 1 0 1 –4 1 0 1 0 Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 255 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 255 255 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 255 255 0 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 255 255 0 255 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 255 255 0 255 510 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 255 255 0 255 510 255 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 255 255 0 255 510 255 0 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 255 255 0 255 510 255 0 255 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 255 255 0 255 510 255 0 255 255 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 255 255 0 255 510 255 0 255 255 0 0 × 1 × 0 × 1 × –4 × 1 × 0 × 1 × 0 × Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 255 510 255 255 0 0 255 255 0 0 0 0 255 255 0 0 Convolution

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0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 255 255 255 0 0 0 255 255 255 0 0 0 255 255 255 510 Convolution

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Edge Detection

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Edge Detection

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Edge Detection

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Edge Detection

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Line Detection

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Line Detection

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0 1 0 1 –4 1 0 1 0

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0 1 0 1 –4 1 0 1 0 Laplace Filter

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Sobel Filter 1 0 –1 2 0 –2 1 0 –1 1 2 1 0 0 0 –1 –2 –1

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1 0 –1 2 0 –2 1 0 –1 Sobel Filter 1 2 1 0 0 0 –1 –2 –1 Gy = Gx = =

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Sobel Filter G = √Gx 2 + Gy 2

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–1 0 1 –2 0 2 –1 0 1

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–1 0 1 –2 0 2 –1 0 1

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–1 0 1 –2 0 2 –1 0 1

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Hough Transform

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y r

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y r θ

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y r θ r = x cos(θ) + y sin (θ)

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θ ~r ~r ~r 0 12 9 3 15 13 11 5 30 13 11 7 45 13 11 8 60 11 11 9 75 9 9 9 90 6 7 9 105 3 4 8 120 0 2 6 135 -3 0 4 150 -6 -3 2 165 -9 -6 0 y

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θ ~r ~r ~r 0 12 9 3 15 13 11 5 30 13 11 7 45 13 11 8 60 11 11 9 75 9 9 9 90 6 7 9 105 3 4 8 120 0 2 6 135 -3 0 4 150 -6 -3 2 165 -9 -6 0 y

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θ ~r ~r ~r 0 12 9 3 15 13 11 5 30 13 11 7 45 13 11 8 60 11 11 9 75 9 9 9 90 6 7 9 105 3 4 8 120 0 2 6 135 -3 0 4 150 -6 -3 2 165 -9 -6 0

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θ ~r ~r ~r 0 12 9 3 15 13 11 5 30 13 11 7 45 13 11 8 60 11 11 9 75 9 9 9 90 6 7 9 105 3 4 8 120 0 2 6 135 -3 0 4 150 -6 -3 2 165 -9 -6 0

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r θ

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r θ

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Performance

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Every Instruction Matters

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Avoid Copying

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Avoid Copying ByteArray

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Avoid Copying ByteArray ByteArray

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class ByteGrid( private val data: ByteArray, private val width: Int, private val height: Int )x

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class ByteGrid( private val data: ByteArray, private val width: Int, private val height: Int )x{ fun get(x: Int, y: Int): Byte }x

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class ByteGrid( private val data: ByteArray, private val width: Int, private val height: Int )x{ fun get(x: Int, y: Int): Byte fun rotate(rotation: Int) }x

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class ByteGrid( private val data: ByteArray, private val width: Int, private val height: Int )x{ fun get(x: Int, y: Int): Byte fun rotate(rotation: Int) fun crop(x: Int, y: Int, width: Int, height: Int) }x

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Avoid Allocating

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fun doWork(image: ByteGrid): ByteGrid

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fun doWork(image: ByteGrid, result: ByteGrid)

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Optimize Kernels

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val KERNEL = arrayOf( arrayOf(0, 1, 0), arrayOf(1, -4, 1), arrayOf(0, 1, 0) ) var sum = 0 for (kernelY in 0 until KERNEL.size) { for (kernelX in 0 until KERNEL[kernelY].size) { sum += KERNEL[kernelY][kernelX] * image.get(x, y) } }

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!// Kernel: !// 0 1 0 !// 1 -4 1 !// 0 1 0 var sum = (image.get(x, y - 1) + image.get(x - 1, y) - 4 * image.get(x, y) + image.get(x + 1, y) + image.get(x, y + 1))