Скачать или смотреть Android camera preview data real time processing

You can think of a number of applications where you have to capture and process the camera preview data several times per second. Live face detection, traffic counting, monitoring, move detection, live false color imaging and so on.

Most android devices provide the camera preview data in a format
which is derived from old analog cameras (YUV-format).
The conversion to a common format (like RGB) needs some computational effort and can be done in several ways:

YUVImage:
From API 8 ("Froyo") Android comes with a YUVImage class which provides conversion from yuv-format to jpg-image. You can choose the compression quality from 1% to 100% . 100% achieves the best image-quality where 1% has the shortest conversion time. Normally you will have to find a compromise between both values.

OpenCV:
OpenCV is a framework specialized for image (and matrices) processing. It is avaliable for the Android platform. OpenCV has a huge number of data conversion routines and supports yuv-rgb.
In contrast to YUVImage the conversion is always lossless !

Renderscript:
"RenderScript provides a platform-independent computation engine that operates at the native level. Use it to accelerate your apps that require extensive computational horsepower." (From: developer.android.com).
When a RenderScript script is executed it makes use of all ressources the device comes with, especially using all CPU and GPU cores. Renderscript is great when your tasks can be parallelized as often is the case of image processing.
Renderscript was added to Android in API 11 ("Honeycomb"), from API 18 ("Jelly Bean") it comes with a predefined script for yuv-rgb conversion (ScriptIntrinsicYuvToRGB). The conversion is lossless.


The app shows yuv-rgb conversion of camera preview data taken
at the Nexus 7 (2013) highest preview size : 1920 x 1080 pixel (= the display resolution):

1. using YuvImage at 50 % jpeg-quality, conversion time ca 220 ms per frame

2. dto. at 1 % jpeg-quality, conversion time ca 200 ms per frame

3. using OpenCV, conversion time ca 80 ms per frame

4. using Renderscript, conversion time ca 15 ms

Renderscript here is clearly the fastest method and can provide (theoretically) 66 Frames per second. However the output is limited as the Nexus 7 has a maximum preview rate of 30 FPS.

App created with Basic4Android

Device : Nexus 7 (2013) "Jelly Bean", not rooted
filmed with Panasonic Lumix FS16