Android OpenGL ES(六)-给相机添加滤镜

    @Override
    public void onSurfaceChanged(GL10 gl, int width, int height) {
        //在这里监听到尺寸的改变。做出对应的变化
        prepareFramebuffer(width, height);
        //...
    }

    //生成frameBuffer的时机
    private void prepareFramebuffer(int width, int height) {
        int[] values = new int[1];
        //申请一个与FrameBuffer绑定的textureId
        GLES20.glGenTextures(1, values, 0);
        mOffscreenTextureId = values[0];
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mOffscreenTextureId);
         // Create texture storage.
        GLES20.glTexImage2D(GLES20.GL_TEXTURE_2D, 0, GLES20.GL_RGBA, width, height, 0,
                GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, null);

        // Set parameters.  We're probably using non-power-of-two dimensions, so
        // some values may not be available for use.
        GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER,
                GLES20.GL_NEAREST);
        GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER,
                GLES20.GL_LINEAR);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S,
                GLES20.GL_CLAMP_TO_EDGE);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T,
                GLES20.GL_CLAMP_TO_EDGE);

        //创建FrameBuffer Object并且绑定它
        GLES20.glGenFramebuffers(1, values, 0);
        mFrameBuffer = values[0];
        GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, mFrameBuffer);

        // 创建RenderBuffer Object并且绑定它
        GLES20.glGenRenderbuffers(1, values, 0);
        mRenderBuffer = values[0];
        GLES20.glBindRenderbuffer(GLES20.GL_RENDERBUFFER, mRenderBuffer);

        //为我们的RenderBuffer申请存储空间
        GLES20.glRenderbufferStorage(GLES20.GL_RENDERBUFFER, GLES20.GL_DEPTH_COMPONENT16, width, height);

        // 将renderBuffer挂载到frameBuffer的depth attachment 上。就上面申请了OffScreenId和FrameBuffer相关联
        GLES20.glFramebufferRenderbuffer(GLES20.GL_FRAMEBUFFER, GLES20.GL_DEPTH_ATTACHMENT, GLES20.GL_RENDERBUFFER, mRenderBuffer);
        // 将text2d挂载到frameBuffer的color attachment上
        GLES20.glFramebufferTexture2D(GLES20.GL_FRAMEBUFFER, GLES20.GL_COLOR_ATTACHMENT0, GLES20.GL_TEXTURE_2D, mOffscreenTextureId, 0);

        // See if GLES is happy with all this.
        int status = GLES20.glCheckFramebufferStatus(GLES20.GL_FRAMEBUFFER);
        if (status != GLES20.GL_FRAMEBUFFER_COMPLETE) {
            throw new RuntimeException("Framebuffer not complete, status=" + status);
        }
        // 先不使用FrameBuffer，将其切换掉。到开始绘制的时候，在绑定回来
        GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);
    }
    
    //在onDrawFrame中添加代码
    @Override
    public void onDrawFrame(GL10 gl) {
        //...省略

        //重新切换到FrameBuffer上。
        GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, mFrameBuffer);
        //这里的绘制，就会将数据挂载到FrameBuffer上了。
        mOesFilter.draw();
        //解除绑定，结束FrameBuffer部分的数据写入
        GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);
        
        //....省略
    }

    @Override
    public void onDrawFrame(GL10 gl) {
         //...省略
        //经过路径处理
        mColorFilter.setTextureId(mOffscreenTextureId);
        mColorFilter.onDrawFrame();
        int outputTextureId = mColorFilter.getOutputTextureId();
        //...省略
    }

代码同上，省略

@Override
    public void onDrawFrame(GL10 gl) {
        //省略...
        //经过滤镜处理
        mColorFilter.setTextureId(mOffscreenTextureId);
        mColorFilter.onDrawFrame();
        int outputTextureId = mColorFilter.getOutputTextureId();

        //将得到的outputTextureId，输入encoder,进行编码
        mVideoEncoder.setTextureId(outputTextureId);

        mVideoEncoder.frameAvailable(mSurfaceTexture);

        //将得到的outputTextureId,再次Draw,因为没有FrameBuffer,所以这次Draw的数据，就直接到了Surface上了。
        mShowFilter.setTextureId(outputTextureId);
        mShowFilter.onDrawFrame();
    }