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)；