OpenGL ES for Android 相机预览
2020-02-17 本文已影响0人
老孟程序员
权限
Android上打开摄像头需要camera权限，在Android 6.0及以上的版本需要动态申请权限，在AndroidManifest.xml中添加camera权限：
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.arvr.sample">
<uses-permission android:name="android.permission.CAMERA"/>
<application>
...
</application>
<uses-permission android:name="android.permission.CAMERA"/> 是camera权限
动态申请camera权限代码如下：
class CameraActivity : AppCompatActivity(), SurfaceTexture.OnFrameAvailableListener {
private lateinit var mRenderer: MyRenderer
override fun onFrameAvailable(surfaceTexture: SurfaceTexture?) {
glSurfaceView.queueEvent {
surfaceTexture?.updateTexImage()
glSurfaceView.requestRender()
}
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.surface)
glSurfaceView.setEGLContextClientVersion(2)
mRenderer = MyRenderer(context = baseContext, listener = this)
glSurfaceView.setRenderer(mRenderer)
glSurfaceView.renderMode = GLSurfaceView.RENDERMODE_WHEN_DIRTY
if (ContextCompat.checkSelfPermission(
this,
Manifest.permission.CAMERA
) != PackageManager.PERMISSION_GRANTED
) {
//没有权限
ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.CAMERA), 100)
} else {
mRenderer.cameraPermission = true
mRenderer.startCamera()
}
}
override fun onRequestPermissionsResult(
requestCode: Int,
permissions: Array<out String>,
grantResults: IntArray
) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults)
if (requestCode == 100 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
mRenderer.cameraPermission = true
mRenderer.startCamera()
}
}
override fun onResume() {
super.onResume()
glSurfaceView.onResume()
}
override fun onPause() {
super.onPause()
glSurfaceView.onPause()
}
}
在onCreate中先判断是否有camera权限，如果没有则申请权限权限 ， 如果有则打开camera。弹出权限申请对话框，用户点击是否允许，不管是同意还是拒绝都会回调onRequestPermissionsResult方法，用户点击同意后打开camera，和已经有权限的操作是一样的。
创建program并获取参数句柄
顶点shader代码如下：
attribute vec4 a_Position;
attribute vec2 a_TexCoordinate;
varying vec2 v_TexCoord;
void main()
{
v_TexCoord = a_TexCoordinate;
gl_Position = a_Position;
}
片段shader代码如下：
#extension GL_OES_EGL_image_external : require
precision mediump float;
uniform samplerExternalOES u_Texture;
varying vec2 v_TexCoord;
void main()
{
gl_FragColor = texture2D(u_Texture, v_TexCoord);
}
<font color='red'>
注意：顶点和片段shader是单独的文件，分别是camera_vs.glsl和camera_fs.glsl，存放于assets/glsl目录下。
</font>
在onSurfaceCreated回调中创建program并获取参数句柄，创建纹理，代码如下：
override fun onSurfaceCreated(p0: GL10?, p1: EGLConfig?) {
createProgram()
//获取vPosition索引
vPositionLoc = GLES20.glGetAttribLocation(mProgramHandle, "a_Position")
texCoordLoc = GLES20.glGetAttribLocation(mProgramHandle, "a_TexCoordinate")
textureLoc = GLES20.glGetUniformLocation(mProgramHandle, "u_Texture")
textureId = GLTools.createOESTextureId()
surfaceTexture = SurfaceTexture(textureId)
surfaceTexture?.setOnFrameAvailableListener(listener)
}
private fun createProgram() {
var vertexCode =
AssetsUtils.readAssetsTxt(
context = context,
filePath = "glsl/camera_vs.glsl"
)
var fragmentCode =
AssetsUtils.readAssetsTxt(
context = context,
filePath = "glsl/camera_fs.glsl"
)
mProgramHandle = GLTools.createAndLinkProgram(vertexCode, fragmentCode)
}
fun createOESTextureId(): Int {
val textures = IntArray(1)
GLES20.glGenTextures(1, textures, 0)
glCheck("texture generate")
GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, textures[0])
glCheck("texture bind")
GLES20.glTexParameterf(
GLES11Ext.GL_TEXTURE_EXTERNAL_OES,
GLES20.GL_TEXTURE_MIN_FILTER,
GLES20.GL_LINEAR.toFloat()
)
GLES20.glTexParameterf(
GLES11Ext.GL_TEXTURE_EXTERNAL_OES,
GLES20.GL_TEXTURE_MAG_FILTER,
GLES20.GL_LINEAR.toFloat()
)
GLES20.glTexParameteri(
GLES11Ext.GL_TEXTURE_EXTERNAL_OES,
GLES20.GL_TEXTURE_WRAP_S,
GLES20.GL_CLAMP_TO_EDGE
)
GLES20.glTexParameteri(
GLES11Ext.GL_TEXTURE_EXTERNAL_OES,
GLES20.GL_TEXTURE_WRAP_T,
GLES20.GL_CLAMP_TO_EDGE
)
return textures[0]
}
GLTools 为工具类，createOESTextureId方法是其中一个方法，创建一个OES纹理，OES纹理用于渲染相机、视频。创建纹理id并创建SurfaceTexture，SurfaceTexture在打开相机方法中用到，用于预览相机。setOnFrameAvailableListener的回调是从Activity中传入，真正的实现在Activity中，
class CameraActivity : AppCompatActivity(), SurfaceTexture.OnFrameAvailableListener {
private lateinit var mRenderer: MyRenderer
override fun onFrameAvailable(surfaceTexture: SurfaceTexture?) {
glSurfaceView.queueEvent {
surfaceTexture?.updateTexImage()
glSurfaceView.requestRender()
}
}
override fun onCreate(savedInstanceState: Bundle?) {
...
mRenderer = MyRenderer(context = baseContext, listener = this)
...
}
...
}
当有新的一帧数据时会回调此方法，更新数据并调用glSurfaceView.requestRender() 重新绘制，也就是重新调用Renderer的onDrawFrame方法。
设置顶点坐标、纹理坐标、索引数据
设置顶点坐标，代码如下：
var vertexBuffer = GLTools.array2Buffer(
floatArrayOf(
-1.0f, 1.0f, 0.0f, // top left
-1.0f, -1.0f, 0.0f, // bottom left
1.0f, -1.0f, 0.0f, // bottom right
1.0f, 1.0f, 0.0f // top right
)
)
设置纹理坐标，代码如下：
var texBuffer = GLTools.array2Buffer(
floatArrayOf(
0.0f, 0.0f,
0.0f, 1.0f,
1.0f, 1.0f,
1.0f, 0.0f
)
)
设置索引数据，代码如下：
var index = shortArrayOf(3, 2, 0, 0, 1, 2)
val indexBuffer = GLTools.array2Buffer(index)
绘制
override fun onDrawFrame(p0: GL10?) {
GLES20.glUseProgram(mProgramHandle)
//设置顶点数据
vertexBuffer.position(0)
GLES20.glEnableVertexAttribArray(vPositionLoc)
GLES20.glVertexAttribPointer(vPositionLoc, 3, GLES20.GL_FLOAT, false, 0, vertexBuffer)
//设置纹理顶点数据
texBuffer.position(0)
GLES20.glEnableVertexAttribArray(texCoordLoc)
GLES20.glVertexAttribPointer(texCoordLoc, 2, GLES20.GL_FLOAT, false, 0, texBuffer)
//设置纹理
GLES20.glActiveTexture(GLES20.GL_TEXTURE0)
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId)
GLES20.glUniform1i(textureLoc, 0)
GLES20.glDrawElements(
GLES20.GL_TRIANGLES,
index.size,
GLES20.GL_UNSIGNED_SHORT,
indexBuffer
)
}
打开camera
打开camera有2个条件：
- 有相机权限。
- SurfaceTexture已经创建完成。
相机权限申请的回调和Renderer中onSurfaceCreated（创建SurfaceTexture的方法）方法都是异步的，也就是说无法知道这2个方法回调的前后顺序，因此需要保存相机权限状态cameraPermission和SurfaceTexture变量surfaceTexture,在2个回调中都调用打开相机方法，在打开相机方法中判断相机权限和SurfaceTexture是否都已经准备完成，是则打开，不是则返回，代码如下：
override fun onSurfaceCreated(p0: GL10?, p1: EGLConfig?) {
...
startCamera()
}
fun startCamera() {
if (!cameraPermission || surfaceTexture == null) {
return
}
val cameraInfo = Camera.CameraInfo()
val cameraCount = Camera.getNumberOfCameras()
for (i in 0 until cameraCount) {
Camera.getCameraInfo(i, cameraInfo)
if (cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
val mCamera = Camera.open(i)
mCamera.setPreviewTexture(surfaceTexture)
//设置分辨率
val parameters = mCamera.parameters
parameters.setPreviewSize(1280, 720)
mCamera.parameters = parameters
//开始预览
mCamera.startPreview()
return
}
}
}
运行效果如下：
运行后发现相机的画面是倒的，这是因为camera本身输出的预览流就是倒的，下面通过矩阵旋转解决此问题，顶点shader修改如下：
attribute vec4 a_Position;
attribute vec2 a_TexCoordinate;
uniform mat4 mMatrix;
varying vec2 v_TexCoord;
void main()
{
v_TexCoord = a_TexCoordinate;
gl_Position = mMatrix * a_Position;
}
增加了mMatrix矩阵。
获取矩阵参数句柄，代码如下：
override fun onSurfaceCreated(p0: GL10?, p1: EGLConfig?) {
createProgram()
...
matrixLoc = GLES20.glGetUniformLocation(mProgramHandle, "mMatrix")
...
}
旋转90度，代码如下：
var mMatrix = FloatArray(16)
override fun onSurfaceChanged(p0: GL10?, width: Int, height: Int) {
GLES20.glViewport(0, 0, width, height)
Matrix.setIdentityM(mMatrix, 0)
Matrix.rotateM(mMatrix,0,90F,0F,0F,1F)
}
设置矩阵参数，代码如下：
override fun onDrawFrame(p0: GL10?) {
...
GLES20.glUniformMatrix4fv(matrixLoc, 1, false, mMatrix, 0)
...
}
运行后发现画面调整正了，但左右镜像，这个时候需要画面绕y轴旋转180度，这样就解决了左右镜像问题，代码如下：
override fun onSurfaceChanged(p0: GL10?, width: Int, height: Int) {
GLES20.glViewport(0, 0, width, height)
Matrix.setIdentityM(mMatrix, 0)
Matrix.rotateM(mMatrix,0,180F,0F,1F,0F)
Matrix.rotateM(mMatrix,0,90F,0F,0F,1F)
}
<font color='red'>
注意，对预览流的操作是先绕z轴旋转90度，使画面调正，然后再绕y轴旋转180度，但写代码的时候要绕y轴旋转180度写在前面。
</font>
最终效果如下：
