android 摄像头预览最简代码
移动端深度学习视觉应用最基本的就要和摄像头打交道，试想一下如果让你设计android的camera接口，你应该怎么设计？
首先摄像机是一种硬件，应该有基本的打开、关闭操作，对应的实现是Camera中的open和close，然后有前后摄像头甚至是三摄、四摄等，应该提供个查询设备信息的接口，对应的实现是Camera.CameraInfo。那怎么把采集到的数据画到控件上去呢？
肯定要从View派生子类，就叫SurfaceView, 为了应用MVC的思想，还应有个SurfaceHolder, 用来控制摄像机的开启和关闭，预览的开启和关闭就是Camera.startPreview()和Camera.stopPreview()，通过Camera.setPreviewDisplay()来将摄像头采集的图像绘制到View空间上. 摄像头每一帧都会来一些数据，怎么取出来处理呢？setPreviewCallback()回调应运而生。
Android在API 23也就是android5.0之后对权限做了大幅度的限制，所有的权限都需要动态申请，23之前只需要在AndroidManifest.xml中添加
对于23以上的机型还要添加动态权限获取
if (!isRequiredPermissionsGranted() && Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
requestPermissions(REQUIRED_PERMISSIONS, REQUEST_PERMISSIONS_CODE);
}详细的步骤见Android Camera1 教程 · 第一章 · 开启相机，接着在layout里加入SurfaceView组件，其用来显示摄像头采集到的画面
public class MainActivity extends Activity {
SurfaceView surfaceview;
SurfaceHolder holder;
Camera mCamera;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
surfaceview=findViewById(R.id.surfaceView);
holder=surfaceview.getHolder();
holder.addCallback(new SurfaceHolder.Callback() {
@Override
public void surfaceCreated(SurfaceHolder holder) {
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
}
});
}
@Override
protected void onResume() {
super.onResume();
mCamera=Camera.open(0);
mCamera.setDisplayOrientation(90);
}
@Override
protected void onPause() {
super.onPause();
if(mCamera != null){
mCamera.stopPreview();
mCamera.release();
}
}
}
TextureView
public class MainActivity extends Activity {
TextureView textureview;
Camera mCamera;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textureview=findViewById(R.id.textureView);
textureview.setSurfaceTextureListener(new TextureView.SurfaceTextureListener() {
@Override
public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
try {
mCamera.setPreviewTexture(surface);
} catch (IOException e) {
e.printStackTrace();
}
mCamera.startPreview();
}
@Override
public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
}
@Override
public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
return false;
}
@Override
public void onSurfaceTextureUpdated(SurfaceTexture surface) {
}
});
}
@Override
protected void onResume() {
super.onResume();
mCamera=Camera.open(0);
mCamera.setDisplayOrientation(90);
}
@Override
protected void onPause() {
super.onPause();
if(mCamera != null){
mCamera.stopPreview();
mCamera.release();
}
}
}
GLSurfaceView
public class MainActivity extends Activity{
Camera mCamera;
GLSurfaceView glview;
int mTextureID = -1;
SurfaceTexture mSurface;
DirectDrawer mDirectDrawer;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
glview=findViewById(R.id.glView);
glview.setEGLContextClientVersion(2);
glview.setRenderer(new GLSurfaceView.Renderer() {
@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
mTextureID = createTextureID();
mSurface = new SurfaceTexture(mTextureID);
mSurface.setOnFrameAvailableListener(new SurfaceTexture.OnFrameAvailableListener() {
@Override
public void onFrameAvailable(SurfaceTexture surfaceTexture) {
glview.requestRender();
}
});
mDirectDrawer = new DirectDrawer(mTextureID);
}
@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
GLES20.glViewport(0, 0, width, height);
try {
mCamera.setPreviewTexture(mSurface);
} catch (IOException e) {
e.printStackTrace();
}
mCamera.startPreview();
}
@Override
public void onDrawFrame(GL10 gl) {
GLES20.glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
mSurface.updateTexImage();
float[] mtx = new float[16];
mSurface.getTransformMatrix(mtx);
mDirectDrawer.draw(mtx);
}
});
glview.setRenderMode(RENDERMODE_WHEN_DIRTY);
}
@Override
protected void onResume() {
super.onResume();
mCamera=Camera.open(0);
mCamera.setDisplayOrientation(90);
glview.bringToFront();
}
@Override
protected void onPause() {
super.onPause();
glview.onPause();
if(mCamera!=null){
mCamera.stopPreview();
mCamera.release();
}
}
private int createTextureID()
{
int[] texture = new int[1];
GLES20.glGenTextures(1, texture, 0);
GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, texture[0]);
GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,
GL10.GL_TEXTURE_MIN_FILTER,GL10.GL_LINEAR);
GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,
GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);
GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,
GL10.GL_TEXTURE_WRAP_S, GL10.GL_CLAMP_TO_EDGE);
GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,
GL10.GL_TEXTURE_WRAP_T, GL10.GL_CLAMP_TO_EDGE);
return texture[0];
}
}
public class DirectDrawer {
private final String vertexShaderCode =
"attribute vec4 vPosition;" +
"attribute vec2 inputTextureCoordinate;" +
"varying vec2 textureCoordinate;" +
"void main()" +
"{"+
"gl_Position = vPosition;"+
"textureCoordinate = inputTextureCoordinate;" +
"}";
private final String fragmentShaderCode =
"#extension GL_OES_EGL_image_external : require\n"+
"precision mediump float;" +
"varying vec2 textureCoordinate;\n" +
"uniform samplerExternalOES s_texture;\n" +
"void main() {" +
" gl_FragColor = texture2D( s_texture, textureCoordinate );\n" +
"}";
private FloatBuffer vertexBuffer, textureVerticesBuffer;
private ShortBuffer drawListBuffer;
private final int mProgram;
private int mPositionHandle;
private int mTextureCoordHandle;
private short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices
// number of coordinates per vertex in this array
private static final int COORDS_PER_VERTEX = 2;
private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex
static float squareCoords[] = {
-1.0f, 1.0f,
-1.0f, -1.0f,
1.0f, -1.0f,
1.0f, 1.0f,
};
static float textureVertices[] = {
0.0f, 1.0f,
1.0f, 1.0f,
1.0f, 0.0f,
0.0f, 0.0f,
};
private int texture;
public DirectDrawer(int texture)
{
this.texture = texture;
// initialize vertex byte buffer for shape coordinates
ByteBuffer bb = ByteBuffer.allocateDirect(squareCoords.length * 4);
bb.order(ByteOrder.nativeOrder());
vertexBuffer = bb.asFloatBuffer();
vertexBuffer.put(squareCoords);
vertexBuffer.position(0);
// initialize byte buffer for the draw list
ByteBuffer dlb = ByteBuffer.allocateDirect(drawOrder.length * 2);
dlb.order(ByteOrder.nativeOrder());
drawListBuffer = dlb.asShortBuffer();
drawListBuffer.put(drawOrder);
drawListBuffer.position(0);
ByteBuffer bb2 = ByteBuffer.allocateDirect(textureVertices.length * 4);
bb2.order(ByteOrder.nativeOrder());
textureVerticesBuffer = bb2.asFloatBuffer();
textureVerticesBuffer.put(textureVertices);
textureVerticesBuffer.position(0);
int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
int fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode);
mProgram = GLES20.glCreateProgram(); // create empty OpenGL ES Program
GLES20.glAttachShader(mProgram, vertexShader); // add the vertex shader to program
GLES20.glAttachShader(mProgram, fragmentShader); // add the fragment shader to program
GLES20.glLinkProgram(mProgram); // creates OpenGL ES program executables
}
public void draw(float[] mtx)
{
GLES20.glUseProgram(mProgram);
GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, texture);
// get handle to vertex shader's vPosition member
mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
// Enable a handle to the triangle vertices
GLES20.glEnableVertexAttribArray(mPositionHandle);
// Prepare the coordinate data
GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, vertexBuffer);
mTextureCoordHandle = GLES20.glGetAttribLocation(mProgram, "inputTextureCoordinate");
GLES20.glEnableVertexAttribArray(mTextureCoordHandle);
// textureVerticesBuffer.clear();
// textureVerticesBuffer.put( transformTextureCoordinates( textureVertices, mtx ));
// textureVerticesBuffer.position(0);
GLES20.glVertexAttribPointer(mTextureCoordHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, textureVerticesBuffer);
GLES20.glDrawElements(GLES20.GL_TRIANGLES, drawOrder.length, GLES20.GL_UNSIGNED_SHORT, drawListBuffer);
// Disable vertex array
GLES20.glDisableVertexAttribArray(mPositionHandle);
GLES20.glDisableVertexAttribArray(mTextureCoordHandle);
}
private int loadShader(int type, String shaderCode){
// create a vertex shader type (GLES20.GL_VERTEX_SHADER)
// or a fragment shader type (GLES20.GL_FRAGMENT_SHADER)
int shader = GLES20.glCreateShader(type);
// add the source code to the shader and compile it
GLES20.glShaderSource(shader, shaderCode);
GLES20.glCompileShader(shader);
return shader;
}
private float[] transformTextureCoordinates( float[] coords, float[] matrix)
{
float[] result = new float[ coords.length ];
float[] vt = new float[4];
for ( int i = 0 ; i < coords.length ; i += 2 ) {
float[] v = { coords[i], coords[i+1], 0 , 1 };
Matrix.multiplyMV(vt, 0, matrix, 0, v, 0);
result[i] = vt[0];
result[i+1] = vt[1];
}
return result;
}
}
参考:
- Android开发中关于摄像头方向的理解
- Android Camera旋转角度总结
- Android Camera1 教程:Camera1Sample
- Android Camera2 教程
- 初识Android OpenGL ES
- 使用OpenGL ES 2.0和GLSurfaceView预览
- 实时获取加速计Accelerometer的信息:sensors-test-android
- Android：LinearLayout布局中Layout_weight的深刻理解
- Android应用CPU实时监控工具-全机型适用:github