Slides from AnDevCon Boston 2014 presentation on building custom camera applications in Android.

1. HUYEN TUE DAO
PROJECT
DATE BY
MAY 30, 2014
SAY CHEESE
BUILDING A CUSTOM CAMERA APPLICATION
360dp
wrap_content
ANDEVCON 2014

2. BUILDING A CUSTOM CAMERA APPLICATION
• Getting Started
• Setting up the Camera
• Taking pictures
• Camera settings
• “New” features in API 14
2

3. ABOUT ME
• Mobile developer: native Android and native iOS (personally I use
Android but no I do not have a “favorite”)
• Computer Engineering, University of MD, College Park
• Marylander living in Colorado
• Gamer (video, board, card, anything): currently Dota 2, Don’t
Starve, Kingdom Rush, 7 Wonders
3

4. TITLE
CUSTOM CAMERA CAPABILITY AND AVAILABILITY
What you want to do
What features
the API supports
Typical for Android development: Build.VERSION etc.
What features
the device camera has
Typical for Android development: use-feature and PackageManager
Specific to camera: querying support level from the Camera class
What you can do

5. THE CUSTOM CAMERA: THE MANIFEST
• Camera application hardware-driven so vital to
separate critical features from optional ones.
• Highly recommended to use specific <uses-feature>
to specify required features. Why?
• <uses-permission
android:name="android.permission.CAMERA" />!
- “This will automatically enforce the <uses-
feature> manifest element for all camera features.”
5

6. THE CUSTOM CAMERA: THE MANIFEST
• Just specifying the camera permission (without any
<uses-feature> specifications) means that a device
would require the following:
- a back-facing camera
- a front-facing camera
- auto-focus
- flash
• If you do not need any of the above, specify <uses-
feature> with android:required=false
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7. TITLE
CAMERA CLASS AND INNER CLASSES
android.hardware.Camera*
Device camera client: setup + access point
Preview callback
Shutter callback
Picture taking callback
!
!
!
Auto Focus callback
Zoom listener
Face detection listener
Camera.CameraInfo
front or back, orientation,
shutter disable
Camera.Parameters
preview, picture output,
“photography stuff”:
features/settings dependent
on the device camera: flash
modes, color effects,
scene modes, white balance,
etc.
Camera.Area
“photography stuff”: focus and
metering, rectangular bounds + weight
Camera.Face
“face stuff”, bounds and feature (left
eye, right eye, mouth) coordinates for
a face identified with face detection,
confidence score
APK 14+: Data objects
Device camera information + settings
Camera.Size
width and height:
picture size, video size,
preview size

8. TITLE
THE CUSTOM CAMERA: CAMERA SETUP
Add a SurfaceView to your
layout for the camera preview.
Implement a
SurfaceHolder.Callback to
listen for #surfaceCreated,
#surfaceChanged, and
#surfaceDestroyed
Pass the callback to the
SurfaceHolder instance of
the SurfaceView.
Open a Camera instance:
Camera#open
Get the Camera.Parameters
and perform any initial setup.
After the preview surface has
been created, call
Camera#setPreviewDisplay
with the SurfaceHolder.
Start the preview:
Camera#startPreview.
wait for surface to be created

9. THE CUSTOM CAMERA: BASIC SETUP
• Things to note about setting up the camera preview:
- The surface is destroyed when the visibility of the
SurfaceView is set to View.INVISIBLE.
- Camera#release will stop the preview
- Camera#stopPreview nulls out callbacks, stops face
detection
- Camera#setPreviewDisplay should be called after the
surface is created. No error, just no preview.
- Any changes to the preview size must be between calls to
Camera#startPreview and Camera#stopPreview
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10. THE CUSTOM CAMERA: PICTURE TAKING
• When the camera is set up, call
takePicture(ShutterCallback,
PictureCallback, PictureCallback,
PictureCallback)!
• PictureCallback parameters = 3 picture formats:
raw (uncompressed), postview, and JPEG.
- Raw and postview availability depends on device
- takePicture stops the camera preview so
Camera#startPreview should be called in/after
callbacks
10

11. THE CUSTOM CAMERA: CAMERA INFO
• CameraInfo: information about a particular device camera
- orientation: angle of rotation when facing the camera for the
camera image to match the natural orientation of the device
- facing: camera direction
- whether the shutter sound can be disabled
• Camera.getCameraInfo: camera IDs are indices 0 to n-1
• Use CameraInfo to swap between front and back
- Use PackageManager to check if a front camera exists unless
you have front camera as a requirement for device
- Close the current camera before swapping
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12. TITLE
DEVICE ORIENTATION VS CAMERA ORIENTATION
Natural device orientation
Natural camera orientation
90° difference

13. THE CUSTOM CAMERA: ROTATION
• Some thoughts on rotation:
- Empirically, trying to work with camera/display
rotation and configuration changes sucks:
- Complicated.
- Orientation changes do not coordinate well
with camera orientation changes.
- Can change the activity orientation change
animation in API 18+).
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14. THE CUSTOM CAMERA: CAMERA INFO
• Recommendation:
- Keep a fixed activity orientation.
- Call Camera#setDisplayOrientation to adjust
for CameraInfo.orientation.
- Use the OrientationEventListener to rotate
the UI.
- Does mean that your application thumbnail may
look sideways in the Recent Apps list.
14

15. THE CUSTOM CAMERA: CAMERA PARAMETERS
• Most of the fun stuff (settings and modes) is set in
Camera.Parameters.
- A couple of features (auto-focus and flash) have <uses-feature>
and PackageManager values.
- Most other features will provide support information via methods
in Camera.Parameters
- Example: getMinExposureCompensation returns 0 if exposure
compensation is unsupported
- Several getters provide lists of valid values for features or
modes that have different value ranges on different devices.
- Note that API level also factors: face detection and metering areas
are API 14+.
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16. THE CUSTOM CAMERA: CAMERA PARAMETERS
• For the most part, Camera.Parameters can be changed while
preview started and will take effect immediately.
• For saving/restoring settings state, handy methods:
Camera.Parameters#flatten and
Camera.Parameters#unflatten
• Important:
- Always call Camera#getParameters, do not hold onto
Camera.Parameters instances
- To actually change parameters, set values on a
Camera.Parameters instance and call Camera#setParameters
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17. THE CUSTOM CAMERA: CAMERA PARAMETERS
• Random tips and observations on Camera.Parameters:
- Auto-focus may cause the flash to activate depending on the
camera and its drivers.
- Setting a scene mode overrides other parameters so if camera
parameters have UI feedback may want to call
Camera#getParameters and update.
• Other common camera/photo features done through
Camera.Parameters:
- GPS coordinates and timestamps for geotagging photos.
- Image size and quality
- Note that image size and preview size are independent
17

18. THE CUSTOM CAMERA: WORKING WITH AREAS
• API 14: Camera.Area and metering areas and focus
areas
• Camera.Area: defines bounds within the viewfinder
for the camera to use in metering and focus
• Camera viewfinder/sensor has its own coordinate
system different from a View’s coordinate system.
• Otherwise, just like setting other camera
parameters
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19. TITLE
VIEWFINDER COORDINATES VS VIEW COORDINATES
1000-1000
1000
-1000
Camera
(0,0)
H
W
View

20. THE CUSTOM CAMERA: FACE DETECTION
• API 14+
• Camera.Face, Camera.FaceDetectionListener,
Camera#startFaceDetection,
Camera#stopFaceDetection!
• Camera.Face camera coordinates of bounds of
face in viewfinder; maybe left eye, right eye, mouth
position; also confidence
• camera/sensor coordinates -> view coordinates
20

21. THANKS SO MUCH
FOR COMING!
!
QUESTIONS?
RANDOMLYTYPING.COM
HUYEN@RANDOMLYTYPING.COM
PRESENTER CONTACT
HUYEN TUE DAO
THINGS TO CHECK OUT
Standford Digital Image Processing Class
http://www.stanford.edu/class/ee368/Android/index.html
!
Android Design in Action
https://www.youtube.com/watch?v=OLSa7fErTAM