Android opencv tutorial1相关问题

一： 最近尝试把Opencv配置在安卓上，具体的配置网上有很多。配置成功后直接用android opencv sdk中的sample作了测试，我用的是里面的tutorial1。
适当修改tutorial1使得demo能从前置摄像头提取视频帧。但是修改后发现从前置摄像头得到的图像的方向不对，若想旋转90则可以通过矩阵转置变换transpose(src, dst)来实现，若想水平或者垂直旋转可以通过opencv的flip函数来实现图像方向的翻转。flip函数的官方api介绍如下

C++: void ocl::flip(const oclMat& src, oclMat& dst, int flipCode)
Parameters:
src – source image.
dst – destination image.
flipCode – specifies how to flip the array: 0 means flipping around the x-axis, positive (e.g., 1) means flipping around y-axis, and negative (e.g., -1) means flipping around both axes.
The function flip flips the array in one of three different ways (row and column indices are 0-based). Supports all data types.

由于此函数属于Core包，所以还需要import org.opencv.core.Core;

最后在onCameraFrame函数中就可以对帧进行翻转了。代码如下

    public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
        Mat srcImg = inputFrame.rgba();
        if (this.getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT)
        { // 竖屏
            // doSomrthing
            Core.flip(srcImg, srcImg, 0);//flip aroud Y-axis
        } else
        {
            // 横屏时dosomething
            Core.flip(srcImg, srcImg, 1);//flip aroud Y-axis
        }
        return srcImg;
    }

二：此外，若只想让Android屏幕横屏显示，可以在Manifest文件增加如下配置

android:screenOrientation="landscape"       android:configChanges="keyboardHidden|orientation"

增加后的完整Manifest文件为：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="**.**.**.**">

    <uses-sdk tools:overrideLibrary="org.opencv"/>
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".Tutorial1Activity"
            android:screenOrientation="landscape"
            android:configChanges="keyboardHidden|orientation" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

    <supports-screens android:resizeable="true"
        android:smallScreens="true"
        android:normalScreens="true"
        android:largeScreens="true"
        android:anyDensity="true" />

    <uses-permission android:name="android.permission.CAMERA"/>

    <uses-feature android:name="android.hardware.camera" android:required="false"/>
    <uses-feature android:name="android.hardware.camera.autofocus" android:required="false"/>
    <uses-feature android:name="android.hardware.camera.front" android:required="false"/>
    <uses-feature android:name="android.hardware.camera.front.autofocus" android:required="false"/>

</manifest>

三： 若在AndroidManifest中没有强制设置app运行的屏幕方向，并想在代码中对横屏和竖屏分别进行处理。可以通过下面的代码来控制

if (this.getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT)
        { // 竖屏
            // doSomrthing
        } else
        {
            // 横屏时dosomething
        }

Configuration在android.content.res.Configuration包中。

四： 从摄像头拿到帧后把Mat转化为byte[]并对图像数据进行操作，操作后回显。可通过如下方式实现。

public Mat onCameraFrame(CvCameraViewFrame inputFrame) {

        Mat srcImg = inputFrame.rgba();
        int t = srcImg.channels();
        int width = srcImg.width();
        int height = srcImg.height();
        int rows = srcImg.rows();
        int cols = srcImg.cols();
        int imgSize = width*height*srcImg.channels();
        byte buff[] = new byte[imgSize];
        byte dstbuff[] = new byte[imgSize];

        srcImg.get(0, 0, buff); //获取srcImg中所有的像素
        //do whatever you want using buff
        srcImg.put(0, 0, dstbuff);//将buff放回原mat，完成对mat的修改操作
        return srcImg;
    }

Reference:
http://blog.youkuaiyun.com/wunghao8/article/details/38868281
http://blog.youkuaiyun.com/watkinsong/article/details/9189649
http://blog.youkuaiyun.com/yangtrees/article/details/38279351
http://my.oschina.net/u/1246663/blog/197626