使用Android Camera2 API和ANativeWindow进行实时图像处理和显示

我需要使用相机预览数据进行一些实时图像处理,例如人脸检测(它是一个c库),然后在屏幕上显示带有人脸的预览预览.

我已经从Android camera2 API – Display processed frame in real time中阅读了http://nezarobot.blogspot.com/2016/03/android-surfacetexture-camera2-opencv.html和Eddy Talvala的答案.在两个网页之后,我设法构建了该应用程序(不调用面部检测库,仅尝试使用ANativeWindow显示预览),但是每次我在Google Pixel上运行此应用程序-7.1 .0-在Genymotion上运行的API 25,该应用程序始终崩溃,并抛出以下日志

08-28 14:23:09.598 2099-2127/tau.camera2demo A/libc: Fatal signal 11 (SIGSEGV), code 2, fault addr 0xd3a96000 in tid 2127 (CAMERA2)
                  [ 08-28 14:23:09.599   117:  117 W/         ]
                  debuggerd: handling request: pid=2099 uid=10067 gid=10067 tid=2127

我用谷歌搜索,但没有找到答案.

Github上的整个项目：https://github.com/Fung-yuantao/android-camera2demo

这是关键代码(我认为).

Camera2Demo.java中的代码：

private void startPreview(CameraDevice camera) throws CameraAccessException {
    SurfaceTexture texture = mPreviewView.getSurfaceTexture();

    // to set PREVIEW size
    texture.setDefaultBufferSize(mPreviewSize.getWidth(),mPreviewSize.getHeight());
    surface = new Surface(texture);
    try {
        // to set request for PREVIEW
        mPreviewBuilder = camera.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }

    mImageReader = ImageReader.newInstance(mImageWidth, mImageHeight, ImageFormat.YUV_420_888, 2);

    mImageReader.setOnImageAvailableListener(mOnImageAvailableListener,mHandler);

    mPreviewBuilder.addTarget(mImageReader.getSurface());

    //output Surface
    List<Surface> outputSurfaces = new ArrayList<>();
    outputSurfaces.add(mImageReader.getSurface());

    /*camera.createCaptureSession(
            Arrays.asList(surface, mImageReader.getSurface()),
            mSessionStateCallback, mHandler);
            */
    camera.createCaptureSession(outputSurfaces, mSessionStateCallback, mHandler);
}


private CameraCaptureSession.StateCallback mSessionStateCallback = new CameraCaptureSession.StateCallback() {

    @Override
    public void onConfigured(CameraCaptureSession session) {
        try {
            updatePreview(session);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onConfigureFailed(CameraCaptureSession session) {

    }
};

private void updatePreview(CameraCaptureSession session)
        throws CameraAccessException {
    mPreviewBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_AUTO);

    session.setRepeatingRequest(mPreviewBuilder.build(), null, mHandler);
}


private ImageReader.OnImageAvailableListener mOnImageAvailableListener = new ImageReader.OnImageAvailableListener() {

    @Override
    public void onImageAvailable(ImageReader reader) {
        // get the newest frame
        Image image = reader.acquireNextImage();

        if (image == null) {
            return;
        }

        // print image format
        int format = reader.getImageFormat();
        Log.d(TAG, "the format of captured frame: " + format);

        // HERE to call jni methods
        JNIUtils.display(image.getWidth(), image.getHeight(), image.getPlanes()[0].getBuffer(), surface);


        //ByteBuffer buffer = image.getPlanes()[0].getBuffer();
        //byte[] bytes = new byte[buffer.remaining()];


        image.close();
    }
};

JNIUtils.java中的代码：

import android.media.Image;
import android.view.Surface;

import java.nio.ByteBuffer;


public class JNIUtils {
    // TAG for JNIUtils class
    private static final String TAG = "JNIUtils";

    // Load native library.
    static {
        System.loadLibrary("native-lib");
    }

    public static native void display(int srcWidth, int srcHeight, ByteBuffer srcBuffer, Surface surface);
}

native-lib.cpp中的代码：

#include <jni.h>
#include <string>
#include <android/log.h>
//#include <android/bitmap.h>
#include <android/native_window_jni.h>

#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, "Camera2Demo", __VA_ARGS__)

extern "C" {
JNIEXPORT jstring JNICALL Java_tau_camera2demo_JNIUtils_display(
        JNIEnv *env,
        jobject obj,
        jint srcWidth,
        jint srcHeight,
        jobject srcBuffer,
        jobject surface) {
    /*
    uint8_t *srcLumaPtr = reinterpret_cast<uint8_t *>(env->GetDirectBufferAddress(srcBuffer));

    if (srcLumaPtr == nullptr) {
        LOGE("srcLumaPtr null ERROR!");
        return NULL;
    }
    */

    ANativeWindow * window = ANativeWindow_fromSurface(env, surface);
    ANativeWindow_acquire(window);

    ANativeWindow_Buffer buffer;

    ANativeWindow_setBuffersGeometry(window, srcWidth, srcHeight, 0/* format unchanged */);

    if (int32_t err = ANativeWindow_lock(window, &buffer, NULL)) {
        LOGE("ANativeWindow_lock failed with error code: %d\n", err);
        ANativeWindow_release(window);
        return NULL;
    }

    memcpy(buffer.bits, srcBuffer,  srcWidth * srcHeight * 4);


    ANativeWindow_unlockAndPost(window);
    ANativeWindow_release(window);

    return NULL;
}
}

在我将memcpy注释掉之后,该应用程序不再崩溃,但什么也不显示.因此,我想问题现在转向如何正确使用memcpy将捕获/处理的缓冲区复制到buffer.bits.

更新：

我改变

memcpy(buffer.bits, srcBuffer, srcWidth * srcHeight * 4);

至

memcpy(buffer.bits, srcLumaPtr, srcWidth * srcHeight * 4);

该应用程序不再崩溃并开始显示,但显示的是奇怪的东西.

解决方法:

如yakobom所述,您尝试将YUV_420_888图像直接复制到RGBA_8888目标(如果未更改,则为默认设置).仅仅使用memcpy是行不通的.

您实际上需要转换数据,并且需要确保不要复制太多-您拥有的示例代码复制了width * height * 4个字节,而YUV_420_888图像仅占用了stride * height * 1.5个字节(大约) .因此,当您复制时,您正在缓冲区末尾运行.

您还必须考虑Java级别提供的跨度,以正确地索引到缓冲区. Microsoft的This link有一个有用的图表.

如果您只关心亮度(因此灰度输出就足够了),只需将亮度通道复制到R,G和B通道中即可.伪代码大致为：

uint8_t *outPtr = buffer.bits;
for (size_t y = 0; y < height; y++) {
   uint8_t *rowPtr = srcLumaPtr + y * srcLumaStride;
   for (size_t x = 0; x < width; x++) {
      *(outPtr++) = *rowPtr;
      *(outPtr++) = *rowPtr;
      *(outPtr++) = *rowPtr;
      *(outPtr++) = 255; // gamma for RGBA_8888
      ++rowPtr;
    }
}

您将需要从Image对象(第一个Plane的行距)读取srcLumaStride,并通过JNI向下传递.

标签：android-camera2,android-ndk,android
来源： https://codeday.me/bug/20191025/1930917.html