我需要使用相机预览数据进行实时图像处理，例如使用c++库进行人脸检测，然后在屏幕上显示加工后的预览并标记人脸。我已阅读了http://nezarobot.blogspot.com/2016/03/android-surfacetexture-camera2-opencv.html和Eddy Talvala在Android camera2 API - Display processed frame in real time中的答案。遵循这两个网页，我成功地构建了该应用程序(没有调用人脸检测库，只是尝试使用ANativeWindow显示预览)，但每次我在运行此应用程序时，在Genymotion上运行的Google Pixel - 7.1.0 - API 25上，该应用程序总是崩溃，并抛出以下日志。
应用程序不再崩溃并开始显示，但它显示了一些奇怪的东西。
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
我在谷歌上搜索了这个问题，但没有找到答案。
Github上的整个项目：https://github.com/Fung-yuantao/android-camera2demo
这里是关键代码（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);
}
在 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;
}
}
在我注释掉memcpy之后，应用程序不再崩溃，但是没有显示任何内容。因此，我猜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中。
更新：
我进行了更改
memcpy(buffer.bits, srcBuffer, srcWidth * srcHeight * 4);
到
memcpy(buffer.bits, srcLumaPtr, srcWidth * srcHeight * 4);
应用程序不再崩溃并开始显示，但它显示了一些奇怪的东西。
ANativeWindow_Buffer中。我刚开始学习 Android。而且互联网上关于 ANativeWindow 的文档很少。 - fytao