Android使用Opengl录像时添加水印

最近需要开发一个类似行车记录仪的app，其中需要给录制的视频添加动态水印。我使用的是OpenGL开发的，刚开始实现的是静态水印，后面才实现的动态水印。

先上效果图，左下角的是静态水印，中间偏下的是时间水印（动态水印）：

一、静态水印

实现原理：录像时是通过OpenGL把图像渲染到GLSurfaceView上的，通俗的讲，就是把图片画到一块画布上，然后展示出来。添加图片水印，就是把水印图片跟录制的图像一起画到画布上。

这是加载纹理跟阴影的Java类

package com.audiovideo.camera.blog;

import android.opengl.GLES20;

/**
 * Created by fenghaitao on 2019/9/12.
 */

public class WaterSignSProgram{

  private static int programId;
  private static final String VERTEX_SHADER =
          "uniform mat4 uMVPMatrix;\n" +
          "attribute vec4 aPosition;\n" +
          "attribute vec4 aTextureCoord;\n" +
          "varying vec2 vTextureCoord;\n" +
          "void main() {\n" +
          "  gl_Position = uMVPMatrix * aPosition;\n" +
          "  vTextureCoord = aTextureCoord.xy;\n" +
          "}\n";

  private static final String FRAGMENT_SHADER =
          "precision mediump float;\n" +
          "varying vec2 vTextureCoord;\n" +
          "uniform sampler2D sTexture;\n" +
          "void main() {\n" +
          "  gl_FragColor = texture2D(sTexture, vTextureCoord);\n" +
          "}\n";

  public WaterSignSProgram() {
    programId = loadShader(VERTEX_SHADER, FRAGMENT_SHADER);

    uMVPMatrixLoc = GLES20.glGetUniformLocation(programId, "uMVPMatrix");
    checkLocation(uMVPMatrixLoc, "uMVPMatrix");
    aPositionLoc = GLES20.glGetAttribLocation(programId, "aPosition");
    checkLocation(aPositionLoc, "aPosition");
    aTextureCoordLoc = GLES20.glGetAttribLocation(programId, "aTextureCoord");
    checkLocation(aTextureCoordLoc, "aTextureCoord");
    sTextureLoc = GLES20.glGetUniformLocation(programId, "sTexture");
    checkLocation(sTextureLoc, "sTexture");
  }

  public int uMVPMatrixLoc;
  public int aPositionLoc;
  public int aTextureCoordLoc;
  public int sTextureLoc;

  public static void checkLocation(int location, String label) {
    if (location < 0) {
      throw new RuntimeException("Unable to locate '" + label + "' in program");
    }
  }

/**
 * 加载编译连接阴影
 * @param vss source of vertex shader
 * @param fss source of fragment shader
 * @return
 */
public static int loadShader(final String vss, final String fss) {
  Log.v(TAG, "loadShader:");
  int vs = GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER);
  GLES20.glShaderSource(vs, vss);
  GLES20.glCompileShader(vs);
  final int[] compiled = new int[1];
  GLES20.glGetShaderiv(vs, GLES20.GL_COMPILE_STATUS, compiled, 0);
  if (compiled[0] == 0) {
   Log.e(TAG, "Failed to compile vertex shader:"
      + GLES20.glGetShaderInfoLog(vs));
   GLES20.glDeleteShader(vs);
   vs = 0;
  }

  int fs = GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER);
  GLES20.glShaderSource(fs, fss);
  GLES20.glCompileShader(fs);
  GLES20.glGetShaderiv(fs, GLES20.GL_COMPILE_STATUS, compiled, 0);
  if (compiled[0] == 0) {
   Log.w(TAG, "Failed to compile fragment shader:"
     + GLES20.glGetShaderInfoLog(fs));
   GLES20.glDeleteShader(fs);
   fs = 0;
  }

  final int program = GLES20.glCreateProgram();
  GLES20.glAttachShader(program, vs);
  GLES20.glAttachShader(program, fs);
  GLES20.glLinkProgram(program);

  return program;
}

  /**
   * terminatinng, this should be called in GL context
   */
  public static void release() {
    if (programId >= 0)
      GLES20.glDeleteProgram(programId);
    programId = -1;
  }
}

package com.audiovideo.camera.blog;

import android.opengl.GLES20;
import android.opengl.Matrix;

import com.audiovideo.camera.glutils.GLDrawer2D;
import com.audiovideo.camera.utils.LogUtil;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;

这是画水印的Java类
/**
 * Created by fenghaitao on 2019/9/12.
 */

public class WaterSignature {

  private static final String VERTEX_SHADER =
      "uniform mat4 uMVPMatrix;\n" +
          "attribute vec4 aPosition;\n" +
          "attribute vec4 aTextureCoord;\n" +
          "varying vec2 vTextureCoord;\n" +
          "void main() {\n" +
          "  gl_Position = uMVPMatrix * aPosition;\n" +
          "  vTextureCoord = aTextureCoord.xy;\n" +
          "}\n";

  private static final String FRAGMENT_SHADER =
      "precision mediump float;\n" +
          "varying vec2 vTextureCoord;\n" +
          "uniform sampler2D sTexture;\n" +
          "void main() {\n" +
          "  gl_FragColor = texture2D(sTexture, vTextureCoord);\n" +
          "}\n";

  public static final int SIZE_OF_FLOAT = 4;
  /**
   * 一个“完整”的正方形，从两维延伸到-1到1。
   * 当 模型/视图/投影矩阵是都为单位矩阵的时候，这将完全覆盖视口。
   * 纹理坐标相对于矩形是y反的。
   * (This seems to work out right with external textures from SurfaceTexture.)
   */
  private static final float FULL_RECTANGLE_COORDS[] = {
      -1.0f, -1.0f,  // 0 bottom left
      1.0f, -1.0f,  // 1 bottom right
      -1.0f, 1.0f,  // 2 top left
      1.0f, 1.0f,  // 3 top right
  };
  private static final float FULL_RECTANGLE_TEX_COORDS[] = {
      0.0f, 1.0f,   //0 bottom left   //0.0f, 0.0f, // 0 bottom left
      1.0f, 1.0f,   //1 bottom right  //1.0f, 0.0f, // 1 bottom right
      0.0f, 0.0f,   //2 top left    //0.0f, 1.0f, // 2 top left
      1.0f, 0.0f,   //3 top right    //1.0f, 1.0f, // 3 top right
  };

  private FloatBuffer mVertexArray;
  private FloatBuffer mTexCoordArray;
  private int mCoordsPerVertex;
  private int mCoordsPerTexture;
  private int mVertexCount;
  private int mVertexStride;
  private int mTexCoordStride;
  private int hProgram;

  public float[] mProjectionMatrix = new float[16];// 投影矩阵
  public float[] mViewMatrix = new float[16]; // 摄像机位置朝向9参数矩阵
  public float[] mModelMatrix = new float[16];// 模型变换矩阵
  public float[] mMVPMatrix = new float[16];// 获取具体物体的总变换矩阵
  private float[] getFinalMatrix() {
    Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
    Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);
    return mMVPMatrix;
  }

  public WaterSignature() {
    mVertexArray = createFloatBuffer(FULL_RECTANGLE_COORDS);
    mTexCoordArray = createFloatBuffer(FULL_RECTANGLE_TEX_COORDS);
    mCoordsPerVertex = 2;
    mCoordsPerTexture = 2;
    mVertexCount = FULL_RECTANGLE_COORDS.length / mCoordsPerVertex; // 4
    mTexCoordStride = 2 * SIZE_OF_FLOAT;
    mVertexStride = 2 * SIZE_OF_FLOAT;

    Matrix.setIdentityM(mProjectionMatrix, 0);
    Matrix.setIdentityM(mViewMatrix, 0);
    Matrix.setIdentityM(mModelMatrix, 0);
    Matrix.setIdentityM(mMVPMatrix, 0);
    hProgram = GLDrawer2D.loadShader(VERTEX_SHADER, FRAGMENT_SHADER);
    GLES20.glUseProgram(hProgram);
  }

  private FloatBuffer createFloatBuffer(float[] coords) {
    ByteBuffer bb = ByteBuffer.allocateDirect(coords.length * SIZE_OF_FLOAT);
    bb.order(ByteOrder.nativeOrder());
    FloatBuffer fb = bb.asFloatBuffer();
    fb.put(coords);
    fb.position(0);
    return fb;
  }

  private WaterSignSProgram mProgram;

  public void setShaderProgram(WaterSignSProgram mProgram) {
    this.mProgram = mProgram;
  }

  public void drawFrame(int mTextureId) {
    GLES20.glUseProgram(hProgram);
    // 设置纹理
    GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mTextureId);
    GLES20.glUniform1i(mProgram.sTextureLoc, 0);
    GlUtil.checkGlError("GL_TEXTURE_2D sTexture");
    // 设置 model / view / projection 矩阵
    GLES20.glUniformMatrix4fv(mProgram.uMVPMatrixLoc, 1, false, getFinalMatrix(), 0);
    GlUtil.checkGlError("glUniformMatrix4fv uMVPMatrixLoc");
    // 使用简单的VAO 设置顶点坐标数据
    GLES20.glEnableVertexAttribArray(mProgram.aPositionLoc);
    GLES20.glVertexAttribPointer(mProgram.aPositionLoc, mCoordsPerVertex,
        GLES20.GL_FLOAT, false, mVertexStride, mVertexArray);
    GlUtil.checkGlError("VAO aPositionLoc");
    // 使用简单的VAO 设置纹理坐标数据
    GLES20.glEnableVertexAttribArray(mProgram.aTextureCoordLoc);
    GLES20.glVertexAttribPointer(mProgram.aTextureCoordLoc, mCoordsPerTexture,
        GLES20.GL_FLOAT, false, mTexCoordStride, mTexCoordArray);
    GlUtil.checkGlError("VAO aTextureCoordLoc");
    // GL_TRIANGLE_STRIP三角形带，这就为啥只需要指出4个坐标点，就能画出两个三角形了。
    GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, mVertexCount);
    // Done -- 解绑~
    GLES20.glDisableVertexAttribArray(mProgram.aPositionLoc);
    GLES20.glDisableVertexAttribArray(mProgram.aTextureCoordLoc);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, 0);
    GLES20.glUseProgram(0);
  }

  /**
   * terminatinng, this should be called in GL context
   */
  public void release() {
    if (hProgram >= 0)
      GLES20.glDeleteProgram(hProgram);
    hProgram = -1;
  }

  /**
   * 删除texture
   */
  public static void deleteTex(final int hTex) {
    LogUtil.v("WaterSignature", "deleteTex:");
    final int[] tex = new int[] {hTex};
    GLES20.glDeleteTextures(1, tex, 0);
  }

}

没时间了。先写到这，后面是调用，迟点再写。

下面是如何把水印绘制到画布上：

1、在SurfaceTexture的onSurfaceCreated方法中初始化并设置阴影；

@Override
   public void onSurfaceCreated(final GL10 unused, final EGLConfig config) {
     LogUtil.v(TAG, "onSurfaceCreated:");
     // This renderer required OES_EGL_image_external extension
     final String extensions = GLES20.glGetString(GLES20.GL_EXTENSIONS);  // API >= 8
   // 使用黄色清除界面
     GLES20.glClearColor(1.0f, 1.0f, 0.0f, 1.0f);
     //设置水印
      if (mWaterSign == null) {
        mWaterSign = new WaterSignature();
      }
      //设置阴影
     mWaterSign.setShaderProgram(new WaterSignSProgram());
    mSignTexId = loadTexture(MyApplication.getContext(), R.mipmap.watermark);
   }

这里是生成mSignTexId 的方法，把该图像与纹理id绑定并返回：

public static int loadTexture(Context context, int resourceId) {
  final int[] textureObjectIds = new int[1];
  GLES20.glGenTextures(1, textureObjectIds, 0);
  if(textureObjectIds[0] == 0){
    Log.e(TAG,"Could not generate a new OpenGL texture object!");
    return 0;
  }
  final BitmapFactory.Options options = new BitmapFactory.Options();
  options.inScaled = false;  //指定需要的是原始数据，非压缩数据
  final Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), resourceId, options);
  if(bitmap == null){
    Log.e(TAG, "Resource ID "+resourceId + "could not be decode");
    GLES20.glDeleteTextures(1, textureObjectIds, 0);
    return 0;
  }
  //告诉OpenGL后面纹理调用应该是应用于哪个纹理对象
  GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureObjectIds[0]);
  //设置缩小的时候（GL_TEXTURE_MIN_FILTER）使用mipmap三线程过滤
  GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR_MIPMAP_LINEAR);
  //设置放大的时候（GL_TEXTURE_MAG_FILTER）使用双线程过滤
  GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR);
  //Android设备y坐标是反向的，正常图显示到设备上是水平颠倒的，解决方案就是设置纹理包装，纹理T坐标（y）设置镜面重复
  //ball读取纹理的时候 t范围坐标取正常值+1
  //GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T, GLES20.GL_MIRRORED_REPEAT);
  GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);
  bitmap.recycle();
  //快速生成mipmap贴图
  GLES20.glGenerateMipmap(GLES20.GL_TEXTURE_2D);
  //解除纹理操作的绑定
  GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, 0);
  return textureObjectIds[0];
}

2、在绘制方法onDrawFrame中绘制画面的同时把水印绘制进去；

/**
    * 绘图到glsurface
    * 我们将rendermode设置为glsurfaceview.rendermode_when_dirty，
    * 仅当调用requestrender时调用此方法（=需要更新纹理时）
    * 如果不在脏时设置rendermode，则此方法的最大调用速度为60fps。
    */
   @Override
   public void onDrawFrame(final GL10 unused) {
     GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
     GLES20.glEnable(GLES20.GL_BLEND);
     //开启GL的混合模式，即图像叠加
     GLES20.glBlendFunc(GLES20.GL_ONE, GLES20.GL_ONE_MINUS_SRC_ALPHA)；
     /**
     *中间这里是你绘制的预览画面
     */
   //画水印（非动态）
    GLES20.glViewport(20, 20, 288, 120);
   mWaterSign.drawFrame(mSignTexId);
    }

这里最重要的是要开启GL的混合模式，即图像叠加，不然你绘制的水印会覆盖原先的预览画面

//开启GL的混合模式，即图像叠加
GLES20.glBlendFunc(GLES20.GL_ONE, GLES20.GL_ONE_MINUS_SRC_ALPHA)；

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