图片流交换是非常常见的需求，为了保证程序的健壮性，可以将这些步骤分为各个进程分别处理，防止中间步骤错误导致主进程crash从而降低用户体验。比如人脸识别、场景识别、直播等场景，这些图片数据可能要经过很多个步骤流转，在各步骤中执行格式转换、图层叠加、图片畸变、颜色矫正等，比如直播中常见的特效和相机图片叠加。

在查阅资料过程中，发现网上相应的资料较少。对我非常有帮助的是一位博主Robot 9写的《基于 HardwareBuffer 实现 Android 多进程渲染》，但我不太想使用aidl来实现跨进程，于是我研究一段时间之后，决定使用Socket+HardwareBuffer来完成跨进程渲染。

实现的效果

最终效果
最终效果

为什么是HardwareBuffer

HardwareBuffer支持Android 8.0（API 级别 26）及以上版本，底层实现就是GraphicBuffer。

  • 跨进程共享内存。该机制允许各个进程之间数据共享，不需要耗费性能的内存拷贝。
  • 支持RGB、YUV等常见格式，因此支持相机等数据高效传输。
  • 对OpenGL、Vulkan等图形API原生支持，可以和常见图形API直接集成，不需要耗费性能的glReadpixels()这些API。

案例示意

架构示意图
架构示意图

简要描述:

  1. 案例分为两个进程：RendererClient客户端和RendererServer服务端，客户端和服务的渲染都是用OpenGLES，后续再附上Vulkan作为服务端渲染的实现。
xxxx:/ # ps -ef | grep com.example.Renderer                  
u0_a83        9645   612 28 01:37:17 ?    00:00:11 com.example.RendererServer
u0_a84        9736   612 17 01:37:23 ?    00:00:06 com.example.RendererClient
root          9949  9433 13 01:37:58 pts/3 00:00:00 grep com.example.Renderer
  1. 首先服务端启动Socket等待连接，然后在启动客户端时执行连接。
  2. 初始化客户端，创建HardwareBuffer，然后将HardwareBuffer关联到EGLImage，还要将该EGLImage作为一个附件挂载到一个帧缓冲FrameBuffer上。
  3. 通过AHardwareBuffer_sendHandleToUnixSocket()将HardwareBuffer发送给服务端。
  4. 服务端接收到HardwareBuffer后，停止等待，并根据该HardwareBuffer初始化自己的EGLImage，然后将该EGLImage作为贴图绘制到四边形中，完成显示。
  5. 上述步骤完成后，就通过HardwareBuffer把客户端和服务端的两个EGLImage关联起来了，后续客户端直接将虚拟场景渲染到帧缓冲中即可。

完整代码：https://gitee.com/xingchen0085/andorid_shared_texture

视频：https://b23.tv/ObMaagI

实现步骤

项目初始结构

使用gradle管理两个Module，RendererServer和RendererClient。

项目结构
项目结构

服务端Socket

在android_app的onCmdHandler中创建一个Socket线程，设置Socket Server。

// Main.cpp
int socketFd = -1;    // 全局变量
int dataSocket = -1;  // 全局变量
void cmd_handler(struct android_app *app, int32_t cmd){
    switch (cmd) {
        case APP_CMD_INIT_WINDOW: {                         // ANativeWindow init
            LOG_D("    APP_CMD_INIT_WINDOW");
            if(socketFd < 0){
                pthread_t serverThread;
                pthread_create(&serverThread, nullptr, SetupServer, nullptr);
            }
            break;
        }
        ...
		...
    }
}

SocketServer实现。

// Main.cpp
void* SetupServer(void* obj){
    int ret;
    struct sockaddr_un serverAddr;
    char socketName[108];

    LOG_I("Start server setup");

    socketFd = socket(AF_UNIX, SOCK_STREAM, 0);
    if(socketFd < 0){
        LOG_E("socket: %s", strerror(errno));
        exit(EXIT_FAILURE);
    }
    LOG_D("socket made.");

    memcpy(&socketName[0], "\0", 1);
    strcpy(&socketName[1], SOCKET_NAME);

    memset(&serverAddr, 0, sizeof(struct sockaddr_un));
    serverAddr.sun_family = AF_UNIX;
    strncpy(serverAddr.sun_path, socketName, sizeof(serverAddr.sun_path) - 1); // max is 108

    ret = bind(socketFd, reinterpret_cast<const sockaddr *>(&serverAddr), sizeof(struct sockaddr_un));
    if(ret < 0){
        LOG_E("bind: %s", strerror(errno));
        exit(EXIT_FAILURE);
    }
    LOG_D("bind made");

    // open 8 back buffers for this demo
    ret = listen(socketFd, 8);
    if(ret < 0){
        LOG_E("listen: %s", strerror(errno));
        exit(EXIT_FAILURE);
    }

    LOG_I("Setup Server complete.");

    while (1){
        // accept
        dataSocket = accept(socketFd, nullptr, nullptr);
        LOG_I("accept dataSocket: %d", dataSocket);
        if(dataSocket < 0){
            LOG_E("accept: %s", strerror(errno));
            break;
        }

        while (1){
            ret = AHardwareBuffer_recvHandleFromUnixSocket(dataSocket, &hwBuffer);
            if(ret != 0){
                LOG_E("recvHandleFromUnixSocket: %d", ret);
                break;
            }
            AHardwareBuffer_Desc desc;
            AHardwareBuffer_describe(hwBuffer, &desc);
            LOG_D("recvHandleFromUnixSocket: %d x %d, layer: %d, format: %d", desc.width, desc.height, desc.layers, desc.format);
        }
    }
    LOG_D("Close dataSocket");

    close(dataSocket);
    return nullptr;
}

客户端Socket

在android_app的onCmdHandler中连接Socket Server。

// Main.cpp
int dataSocket = -1;  // 全局变量
void cmd_handler(struct android_app *app, int32_t cmd){
    switch (cmd) {
        case APP_CMD_INIT_WINDOW: {                         // ANativeWindow init
            LOG_D("    APP_CMD_INIT_WINDOW");
            if(dataSocket < 0){
                SetupClient();
                ...
                ...
            }
            break;
        }
        ...
		...
    }
}

连接Socket的实现。

// Main.cpp
void SetupClient(){
    char socketName[108];
    struct sockaddr_un serverAddr;

    dataSocket = socket(AF_UNIX, SOCK_STREAM, 0);
    if(dataSocket < 0){
        LOG_E("socket: %s", strerror(errno));
        exit(EXIT_FAILURE);
    }

    memcpy(&socketName[0], "\0", 1);
    strcpy(&socketName[1], SOCKET_NAME);

    memset(&serverAddr, 0, sizeof(struct sockaddr_un));
    serverAddr.sun_family = AF_UNIX;
    strncpy(serverAddr.sun_path, socketName, sizeof(serverAddr.sun_path) - 1);

    // connect
    int ret = connect(dataSocket, reinterpret_cast<const sockaddr *>(&serverAddr), sizeof(struct sockaddr_un));
    if(ret < 0){
        LOG_E("connect: %s", strerror(errno));
        exit(EXIT_FAILURE);
    }

    LOG_I("Client Setup complete.");
}

客户端创建HardwareBuffer

// Main.cpp
int dataSocket = -1;  // 全局变量
void cmd_handler(struct android_app *app, int32_t cmd){
    switch (cmd) {
        case APP_CMD_INIT_WINDOW: {                         // ANativeWindow init
            LOG_D("    APP_CMD_INIT_WINDOW");
            if(dataSocket < 0){
                SetupClient();
                AHardwareBuffer_Desc hwDesc;
                hwDesc.format = AHARDWAREBUFFER_FORMAT_R8G8B8A8_UNORM;
                hwDesc.width = 1024;
                hwDesc.height = 1024;
                hwDesc.layers = 1;
                hwDesc.rfu0 = 0;
                hwDesc.rfu1 = 0;
                hwDesc.stride = 0;
                hwDesc.usage = AHARDWAREBUFFER_USAGE_CPU_READ_NEVER | AHARDWAREBUFFER_USAGE_CPU_WRITE_NEVER
                               | AHARDWAREBUFFER_USAGE_GPU_COLOR_OUTPUT | AHARDWAREBUFFER_USAGE_GPU_SAMPLED_IMAGE;
                int rtCode = AHardwareBuffer_allocate(&hwDesc, &hwBuffer);
                if(rtCode != 0 || !hwBuffer){
                    LOG_E("Failed to allocate hardware buffer.");
                    exit(EXIT_FAILURE);
                }
            }
            break;
        }
        ...
		...
    }
}

AHardwareBuffer_Desc的几个参数解释：

  • format : 格式可以是RGB、YUV的格式，我们案例中需要处理的RGBA数据，所以设置为AHARDWAREBUFFER_FORMAT_R8G8B8A8_UNORM。
  • width : 宽度，对应的就是传输的纹理宽度，这里固定为1024；
  • height : 高度，对应的就是传输的纹理高度，这里固定为1024；
  • usage ：用途，这几个参数意味着这个HardwareBuffer不提供CPU读写，只给GPU作为颜色附件或作为贴图使用。

客户端创建EGLImage和帧缓冲

创建一个ClientRenderer

#pragma once
#include <cstdint>
#include <string>
#include <vector>
#include <android/asset_manager.h>
#include <EGL/egl.h>
#define EGL_EGLEXT_PROTOTYPES
#define GL_GLEXT_PROTOTYPES
#include <EGL/eglext.h>
#include <GLES2/gl2.h>
#include <GLES2/gl2ext.h>
#include <GLES2/gl2platform.h>
#include <android/hardware_buffer.h>

class ClientRenderer{
public:
    static ClientRenderer* GetInstance();

    void Init(AHardwareBuffer *hwBuffer, int dataSocket);
    void Destroy();
    void Draw();

    AAssetManager *m_NativeAssetManager;
    struct android_app *m_GlobalApp;
private:
    ClientRenderer() = default;

    int InitEGLEnv();
    void DestroyEGLEnv();

    void CreateProgram();
    int ReadShader(const char *fileName, std::vector<char> &source) const;

    static ClientRenderer s_Renderer;

    EGLDisplay m_EglDisplay = EGL_NO_DISPLAY;
    EGLSurface m_EglSurface = EGL_NO_SURFACE;
    EGLContext m_EglContext = EGL_NO_CONTEXT;
    EGLConfig m_EglConfig;

    GLint m_VertexShader;
    GLint m_FragShader;
    GLuint m_Program;
    uint32_t m_ImgWidth = 1024;
    uint32_t m_ImgHeight = 1024;

    GLuint m_OutputFBO;
    GLuint m_OutputTexture;
    EGLImageKHR m_NativeBufferImage;
};

实现OpenGLES和EGL的环境配置

//ClientRenderer.cpp
int ClientRenderer::InitEGLEnv() {
    const EGLint confAttr[] = {
            EGL_RENDERABLE_TYPE, EGL_OPENGL_ES3_BIT_KHR,
            EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
            EGL_RED_SIZE,   8,
            EGL_GREEN_SIZE, 8,
            EGL_BLUE_SIZE,  8,
            EGL_ALPHA_SIZE, EGL_DONT_CARE,
            EGL_DEPTH_SIZE, EGL_DONT_CARE,
            EGL_STENCIL_SIZE, EGL_DONT_CARE,
            EGL_NONE
    };

    // EGL context attributes
    const EGLint ctxAttr[] = {
            EGL_CONTEXT_CLIENT_VERSION, 2,
            EGL_NONE
    };

    EGLint eglMajVers, eglMinVers;
    EGLint numConfigs;
    int resultCode = 0;
    do {
        m_EglDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
        if(m_EglDisplay == EGL_NO_DISPLAY) {
            //Unable to open connection to local windowing system
            LOG_E("BgRender::CreateGlesEnv Unable to open connection to local windowing system");
            resultCode = -1;
            break;
        }

        if(!eglInitialize(m_EglDisplay, &eglMajVers, &eglMinVers)) {
            // Unable to initialize EGL. Handle and recover
            LOG_E("BgRender::CreateGlesEnv Unable to initialize EGL");
            resultCode = -1;
            break;
        }
        LOG_I("BgRender::CreateGlesEnv EGL init with version %d.%d", eglMajVers, eglMinVers);

        if(!eglChooseConfig(m_EglDisplay, confAttr, &m_EglConfig, 1, &numConfigs)) {
            LOG_E("BgRender::CreateGlesEnv some config is wrong");
            resultCode = -1;
            break;
        }

        m_EglSurface = eglCreateWindowSurface(m_EglDisplay, m_EglConfig, m_GlobalApp->window, nullptr);
        if(m_EglSurface == EGL_NO_SURFACE) {
            switch(eglGetError()) {
                case EGL_BAD_ALLOC:
                    // Not enough resources available. Handle and recover
                    LOG_E("BgRender::CreateGlesEnv Not enough resources available");
                    break;
                case EGL_BAD_CONFIG:
                    // Verify that provided EGLConfig is valid
                    LOG_E("BgRender::CreateGlesEnv provided EGLConfig is invalid");
                    break;
                case EGL_BAD_PARAMETER:
                    // Verify that the EGL_WIDTH and EGL_HEIGHT are
                    // non-negative values
                    LOG_E("BgRender::CreateGlesEnv provided EGL_WIDTH and EGL_HEIGHT is invalid");
                    break;
                case EGL_BAD_MATCH:
                    // Check window and EGLConfig attributes to determine
                    // compatibility and pbuffer-texture parameters
                    LOG_E("BgRender::CreateGlesEnv Check window and EGLConfig attributes");
                    break;
            }
        }

        m_EglContext = eglCreateContext(m_EglDisplay, m_EglConfig, EGL_NO_CONTEXT, ctxAttr);
        if(m_EglContext == EGL_NO_CONTEXT) {
            EGLint error = eglGetError();
            if(error == EGL_BAD_CONFIG) {
                // Handle error and recover
                LOG_E("BgRender::CreateGlesEnv EGL_BAD_CONFIG");
                resultCode = -1;
                break;
            }
        }

        if(!eglMakeCurrent(m_EglDisplay, m_EglSurface, m_EglSurface, m_EglContext)) {
            LOG_E("BgRender::CreateGlesEnv MakeCurrent failed");
            resultCode = -1;
            break;
        }
        LOG_E("BgRender::CreateGlesEnv initialize success!");
    } while (false);

    if (resultCode != 0){
        LOG_E("BgRender::CreateGlesEnv fail");
    }
    return resultCode;
}

初始化着色器

// client.vert
#version 300 es
layout(location=0) in vec2 a_position;
layout(location=1) in vec4 a_color;
layout(location=2) in vec2 a_texcoord;

uniform mat4 modelMat;

out vec4 v_color;
out vec2 v_texcoord;
void main(){
    gl_Position = modelMat * vec4(a_position, 0.0, 1.0);
    v_color = a_color;
    v_texcoord = a_texcoord;
}

//client.frag
#version 300 es
precision mediump float;
in vec4 v_color;
in vec2 v_texcoord;

out vec4 FragColor;

void main() {
    FragColor = v_color;
}

创建Program，具体实现略过。

void ClientRenderer::CreateProgram() {
    std::vector<char> vsSource, fsSource;
    if(ReadShader("shaders/client.vert", vsSource) < 0){
        LOG_E("read shader error.");
        return;
    }
    if(ReadShader("shaders/client.frag", fsSource) < 0){
        LOG_E("read shader error.");
        return;
    }
    m_VertexShader = CreateGLShader(std::string(vsSource.data(), vsSource.size()).data(), GL_VERTEX_SHADER);
    m_FragShader = CreateGLShader(std::string(fsSource.data(), fsSource.size()).data(), GL_FRAGMENT_SHADER);
    m_Program = CreateGLProgram(m_VertexShader, m_FragShader);
}

初始化帧缓冲和EGLImage

//ClientRenderer.cpp
void ClientRenderer::Init(AHardwareBuffer *hwBuffer, int dataSocket) {
    DEBUG_LOG();
    if(InitEGLEnv() != 0) return;
    CreateProgram();

    /////////////////////////////////////////////////////////////////////////////////////////////
    //          Main point: FrameBuffer & EGLImage											   //
    /////////////////////////////////////////////////////////////////////////////////////////////
    glGenFramebuffers(1, &m_OutputFBO);
    glBindFramebuffer(GL_FRAMEBUFFER, m_OutputFBO);
    glGenTextures(1, &m_OutputTexture);
    glBindTexture(GL_TEXTURE_2D, m_OutputTexture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, m_ImgWidth, m_ImgHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_OutputTexture, 0);
    uint32_t fboStatus = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    if(fboStatus != GL_FRAMEBUFFER_COMPLETE){
        LOG_E("func %s, line %d, OpenGL renderFramebuffer NOT COMPLETE: %d", __func__, __LINE__, fboStatus);
    }

    // 1、HardwareBuffer ---> EGLClientBuffer
    EGLClientBuffer clientBuffer = eglGetNativeClientBufferANDROID(hwBuffer);
    EGLint eglImageAttributes[] = { EGL_IMAGE_PRESERVED_KHR, EGL_TRUE, EGL_NONE };
    m_NativeBufferImage = eglCreateImageKHR(m_EglDisplay, EGL_NO_CONTEXT, EGL_NATIVE_BUFFER_ANDROID, clientBuffer, eglImageAttributes);
    glBindTexture(GL_TEXTURE_2D, m_OutputTexture);
    glEGLImageTargetTexture2DOES(GL_TEXTURE_2D, m_NativeBufferImage);
    glBindTexture(GL_TEXTURE_2D, 0);
    glBindFramebuffer(GL_FRAMEBUFFER, 0);

    // 2、sendHandleToUnixSocket
    AHardwareBuffer_sendHandleToUnixSocket(hwBuffer, dataSocket);
}

除了常规的创建OpenGLES帧缓冲外，这里的重点有两个：

  1. 将HardwareBuffer和EGLImage关联，直接与GPU交互，不需要内存拷贝。

    EGLClientBuffer clientBuffer = eglGetNativeClientBufferANDROID(hwBuffer);
EGLint eglImageAttributes[] = { EGL_IMAGE_PRESERVED_KHR, EGL_TRUE, EGL_NONE };
m_NativeBufferImage = eglCreateImageKHR(m_EglDisplay, EGL_NO_CONTEXT, EGL_NATIVE_BUFFER_ANDROID, clientBuffer, eglImageAttributes);

  2. 通过sendHandleToUnixSocket将HardwareBuffer传输给SocketServer，SocketServer通过下边的 服务端获取HardwareBuffer 这一步骤获取Buffer。

客户端渲染

客户端渲染比较简单，就是渲染一个彩色四边形，随着时间围绕Z轴旋转。

//ClientRenderer.cpp
//#define RENDER_TO_SCREEN
void ClientRenderer::Draw() {
    glUseProgram(m_Program);
    {
        float x_scale = 0.8f;
        float y_scale = 0.8f;
        GLfloat vertices[] = {
                -1.f * x_scale, -1.f * y_scale,
                1.f * x_scale, -1.f * y_scale,
                -1.f * x_scale, 1.f * y_scale,
                1.f * x_scale, 1.f * y_scale,
        };
        GLfloat colors[] = {
                1.f, 0.f, 0.f, 1.f,
                0.f, 1.f, 0.f, 1.f,
                0.f, 0.f, 1.f, 1.f,
                1.f, 1.f, 1.f, 1.f
        };
        GLfloat texCoords[] = {
                0.0f, 0.0f,
                1.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 1.0f
        };
        GLuint posLoc = glGetAttribLocation(m_Program, "a_position");
        glEnableVertexAttribArray(posLoc);
        glVertexAttribPointer(posLoc, 2, GL_FLOAT, GL_FALSE, 0, vertices);

        GLuint colorLoc = glGetAttribLocation(m_Program, "a_color");
        glEnableVertexAttribArray(colorLoc);
        glVertexAttribPointer(colorLoc, 4, GL_FLOAT, GL_FALSE, 0, colors);

        GLuint texcoordLoc = glGetAttribLocation(m_Program, "a_texcoord");
        glEnableVertexAttribArray(texcoordLoc);
        glVertexAttribPointer(texcoordLoc, 2, GL_FLOAT, GL_FALSE, 0, texCoords);
    }

    glClearColor(0.1f, 0.2f, 0.3f, 1.f);
    glClear(GL_COLOR_BUFFER_BIT);
    glViewport(0, 0, m_ImgHeight, m_ImgHeight);
    glScissor(0, 0, m_ImgWidth, m_ImgHeight);

#ifndef RENDER_TO_SCREEN
    glBindFramebuffer(GL_FRAMEBUFFER, m_OutputFBO);
    glViewport(0, 0, m_ImgHeight, m_ImgHeight);
    glScissor(0, 0, m_ImgWidth, m_ImgHeight);
#endif
    glClearColor(0.8f, 0.2f, 0.3f, 1.f);
    glClear(GL_COLOR_BUFFER_BIT);

    float timeSec = getTimeSec();
    glm::mat4 modeMat = glm::rotate(glm::mat4(1.f), sinf(timeSec), glm::vec3(0, 0, 1));
    glUniformMatrix4fv(glGetUniformLocation(m_Program, "modelMat"), 1, GL_FALSE, glm::value_ptr(modeMat));

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

#ifndef RENDER_TO_SCREEN
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
#endif

    glUseProgram(0);
    eglSwapBuffers(m_EglDisplay, m_EglSurface);
}

服务端获取HardwareBuffer

在Sever端的等待连接循环中，获取客户端传递的dataSocket，转换为HardwareBuffer。

//Main.cpp
void* SetupServer(void* obj){
    ...
    ...

    LOG_I("Setup Server complete.");

    while (1){
        ...
        ...
        while (1){
            ret = AHardwareBuffer_recvHandleFromUnixSocket(dataSocket, &hwBuffer);
            if(ret != 0){
                LOG_E("recvHandleFromUnixSocket: %d", ret);
                break;
            }
            AHardwareBuffer_Desc desc;
            AHardwareBuffer_describe(hwBuffer, &desc);
            LOG_D("recvHandleFromUnixSocket: %d x %d, layer: %d, format: %d", desc.width, desc.height, desc.layers, desc.format);
        }
    }
	...
    ...
}

服务端渲染

创建一个ServerRenderer

#pragma once
#include <cstdint>
#include <string>
#include <vector>
#include <android/asset_manager.h>
#include <EGL/egl.h>
#define EGL_EGLEXT_PROTOTYPES
#define GL_GLEXT_PROTOTYPES
#include <EGL/eglext.h>
#include <GLES2/gl2.h>
#include <GLES2/gl2ext.h>
#include <GLES2/gl2platform.h>
#include <android/hardware_buffer.h>

class ServerRenderer{
public:
    static ServerRenderer* GetInstance();

    void Init(AHardwareBuffer *hwBuffer);
    void Destroy();
    void Draw();

    AAssetManager *m_NativeAssetManager;
    struct android_app *m_GlobalApp;
private:
    ServerRenderer() = default;
    uint8_t* ReaderImage(const char *fileName, size_t *outFileLength);

    int InitEGLEnv();
    void DestroyEGLEnv();

    void CreateProgram();
    int ReadShader(const char *fileName, std::vector<char> &source) const;

    static ServerRenderer s_Renderer;

    EGLDisplay m_EglDisplay = EGL_NO_DISPLAY;
    EGLSurface m_EglSurface = EGL_NO_SURFACE;
    EGLContext m_EglContext = EGL_NO_CONTEXT;
    EGLConfig m_EglConfig;

    GLint m_VertexShader;
    GLint m_FragShader;
    GLuint m_Program;
    uint32_t m_ImgWidth = 1024;
    uint32_t m_ImgHeight = 1024;

    GLuint m_InputTexture;
    EGLImageKHR m_NativeBufferImage;
};

初始化着色器

//server.vert
#version 300 es
layout(location=0) in vec2 a_position;
layout(location=1) in vec4 a_color;
layout(location=2) in vec2 a_texcoord;
out vec4 v_color;
out vec2 v_texcoord;
void main(){
    gl_Position = vec4(a_position, 0.0, 1.0);
    v_color = a_color;
    v_texcoord = a_texcoord;
}

//server.frag
#version 300 es
precision mediump float;
precision mediump sampler2D;

in vec4 v_color;
in vec2 v_texcoord;
uniform sampler2D tex;
out vec4 FragColor;
void main() {
    FragColor = vec4(texture(tex, v_texcoord).rgb, 1.f);
}

接下来初始化OpenGL/EGL、创建Program跟客户端实现一致，略过。

初始化EGLImage

//ServerRenderer.cpp
void ServerRenderer::Init(AHardwareBuffer *hwBuffer) {
    DEBUG_LOG();

    if(InitEGLEnv() != 0) return;
    CreateProgram();

    glGenTextures(1, &m_InputTexture);
    if(hwBuffer && m_NativeBufferImage == nullptr){
        EGLClientBuffer clientBuffer = eglGetNativeClientBufferANDROID(hwBuffer);
        EGLint eglImageAttributes[] = { EGL_IMAGE_PRESERVED_KHR, EGL_TRUE, EGL_NONE };
        m_NativeBufferImage = eglCreateImageKHR(m_EglDisplay, EGL_NO_CONTEXT, EGL_NATIVE_BUFFER_ANDROID, clientBuffer, eglImageAttributes);
        glBindTexture(GL_TEXTURE_2D, m_InputTexture);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glEGLImageTargetTexture2DOES(GL_TEXTURE_2D, m_NativeBufferImage);
        glBindTexture(GL_TEXTURE_2D, 0);
    }
}

渲染贴图

//ServerRenderer.cpp
void ServerRenderer::Draw() {
    glUseProgram(m_Program);
    {
        float x_scale = 0.8f;
        float y_scale = 0.8f;
        GLfloat vertices[] = {
                -1.f * x_scale, -1.f * y_scale,
                1.f * x_scale, -1.f * y_scale,
                -1.f * x_scale, 1.f * y_scale,
                1.f * x_scale, 1.f * y_scale,
        };
        GLfloat colors[] = {
                1.f, 0.f, 0.f, 1.f,
                0.f, 1.f, 0.f, 1.f,
                0.f, 0.f, 1.f, 1.f,
                1.f, 1.f, 1.f, 1.f
        };
        GLfloat texCoords[] = {
                0.0f, 0.0f,
                1.0f, 0.0f,
                0.0f, 1.0f,
                1.0f, 1.0f
        };
        GLuint posLoc = glGetAttribLocation(m_Program, "a_position");
        glEnableVertexAttribArray(posLoc);
        glVertexAttribPointer(posLoc, 2, GL_FLOAT, GL_FALSE, 0, vertices);

        GLuint colorLoc = glGetAttribLocation(m_Program, "a_color");
        glEnableVertexAttribArray(colorLoc);
        glVertexAttribPointer(colorLoc, 4, GL_FLOAT, GL_FALSE, 0, colors);

        GLuint texcoordLoc = glGetAttribLocation(m_Program, "a_texcoord");
        glEnableVertexAttribArray(texcoordLoc);
        glVertexAttribPointer(texcoordLoc, 2, GL_FLOAT, GL_FALSE, 0, texCoords);
    }

    glClearColor(0.f, 0.f, 0.f, 1.f);
    glClear(GL_COLOR_BUFFER_BIT);

    glUniform1i(glGetUniformLocation(m_Program, "tex"), 0);
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, m_InputTexture);

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
    eglSwapBuffers(m_EglDisplay, m_EglSurface);
    glUseProgram(0);
}

核心就是将EGLImage作为贴图给到一个四边形做采样，这样就是把客户端渲染内容“贴“上去啦！

运行

  1. 安装两个APK。
 adb install -t -f RendererServer-debug.apk
 adb install -t -f RendererClient-debug.apk
  1. 先运行RendererServer。
adb shell am start -n com.example.RendererServer/android.app.NativeActivity

这个时候，服务端因为没开始渲染，应该是一个黑屏状态。可以看到👇日志输出:

01:37:31.581 14336-14358 RendererServer        D  ----------------------------------------------------------------
01:37:31.581 14336-14358 RendererServer        D      android_main()
01:37:31.582 14336-14336 threaded_app          V  Start: 0xb40000746cec61f0
01:37:31.582 14336-14358 threaded_app          V  activityState=10
01:37:31.583 14336-14336 threaded_app          V  Resume: 0xb40000746cec61f0
01:37:31.583 14336-14358 threaded_app          V  activityState=11
01:37:31.590 14336-14336 threaded_app          V  InputQueueCreated: 0xb40000746cec61f0 -- 0xb40000748ce9b560
01:37:31.590 14336-14358 threaded_app          V  APP_CMD_INPUT_CHANGED
01:37:31.590 14336-14358 threaded_app          V  Attaching input queue to looper
01:37:31.601 14336-14336 threaded_app          V  NativeWindowCreated: 0xb40000746cec61f0 -- 0xb40000752cea0a70
01:37:31.601 14336-14358 threaded_app          V  APP_CMD_INIT_WINDOW
01:37:31.601 14336-14358 RendererServer        D      APP_CMD_INIT_WINDOW
01:37:31.601 14336-14361 RendererServer        I  Start server setup
01:37:31.601 14336-14361 RendererServer        D  socket made.
01:37:31.601 14336-14361 RendererServer        D  bind made
01:37:31.601 14336-14361 RendererServer        I  Setup Server complete.
  1. 再运行RendererClient
adb shell am start -n com.example.RendererClient/android.app.NativeActivity

可以看到👇日志输出:

01:40:35.691 14853-14877 RendererClient        D  ----------------------------------------------------------------
01:40:35.691 14853-14877 RendererClient        D      android_main()
01:40:35.692 14853-14853 threaded_app          V  Start: 0xb40000746cec61f0
01:40:35.692 14853-14877 threaded_app          V  activityState=10
01:40:35.693 14853-14853 threaded_app          V  Resume: 0xb40000746cec61f0
01:40:35.693 14853-14877 threaded_app          V  activityState=11
01:40:35.700 14853-14853 threaded_app          V  InputQueueCreated: 0xb40000746cec61f0 -- 0xb40000748ce9b560
01:40:35.700 14853-14877 threaded_app          V  APP_CMD_INPUT_CHANGED
01:40:35.700 14853-14877 threaded_app          V  Attaching input queue to looper
01:40:35.714 14853-14853 threaded_app          V  NativeWindowCreated: 0xb40000746cec61f0 -- 0xb40000752cea0a70
01:40:35.714 14853-14877 threaded_app          V  APP_CMD_INIT_WINDOW
01:40:35.714 14853-14877 RendererClient        D      APP_CMD_INIT_WINDOW
01:40:35.715 14853-14877 RendererClient        I  Client Setup complete.
01:40:35.715 14811-14835 RendererServer        I  accept dataSocket: 76

这里可以看到Client Setup complete.，表示我们的Socket连接成功。然后在Server端也打出来日志：accept dataSocket: 76，表示已处理完客户端连接。

  1. 我们切换到RendererServer界面，就可以看到客户端提交的渲染画面了。

动图效果
动图效果

日志也打印了服务端获取的HardwareBuffer信息：

RendererServer        D  recvHandleFromUnixSocket: 1024 x 1024, layer: 1, format: 1

待完善

以下这三点还没有完善，如果大家感兴趣，后续我会添加这些内容。

  1. 开启和关闭Socket的时机需要完善，目前如果重复进入Client，会黑屏。
  2. 启动Client后无需切换到Server界面，Server是一个后台进程，直接提供渲染即可。
  3. HardwareBuffer的创建应在Server端完成，然后传递给客户端。
  4. Vulkan实现。

参考