NativeImage开发指导

场景介绍

NativeImage是提供Surface关联OpenGL外部纹理的模块，表示图形队列的消费者端。开发者可以通过NativeImage接口接收和使用Buffer，并将Buffer关联输出到OpenGL外部纹理。针对NativeImage，常见的开发场景如下：

通过NativeImage提供的Native API接口创建NativeImage实例作为消费者端，获取与该实例对应的NativeWindow作为生产者端。NativeWindow相关接口可用于填充Buffer内容并提交，NativeImage将Buffer内容更新到OpenGL外部纹理上。本模块需要配合NativeWindow、NativeBuffer、EGL、GLES3模块一起使用。

接口说明

接口名	描述
OH_NativeImage_Create (uint32_t textureId, uint32_t textureTarget)	创建一个OH_NativeImage实例，该实例与OpenGL ES的纹理ID和纹理目标相关联。
OH_NativeImage_AcquireNativeWindow (OH_NativeImage *image)	获取与OH_NativeImage相关联的OHNativeWindow指针，该OHNativeWindow后续不再需要时需要调用 OH_NativeWindow_DestroyNativeWindow释放。
OH_NativeImage_AttachContext (OH_NativeImage *image, uint32_t textureId)	将OH_NativeImage实例附加到当前OpenGL ES上下文，且该OpenGL ES纹理会绑定到 GL_TEXTURE_EXTERNAL_OES，并通过OH_NativeImage进行更新。
OH_NativeImage_DetachContext (OH_NativeImage *image)	将OH_NativeImage实例从当前OpenGL ES上下文分离。
OH_NativeImage_UpdateSurfaceImage (OH_NativeImage *image)	通过OH_NativeImage获取最新帧更新相关联的OpenGL ES纹理。
OH_NativeImage_GetTimestamp (OH_NativeImage *image)	获取最近调用OH_NativeImage_UpdateSurfaceImage的纹理图像的相关时间戳。
OH_NativeImage_GetTransformMatrix (OH_NativeImage *image, float matrix[16])	获取最近调用OH_NativeImage_UpdateSurfaceImage的纹理图像的变化矩阵。
OH_NativeImage_Destroy (OH_NativeImage **image)	销毁通过OH_NativeImage_Create创建的OH_NativeImage实例，销毁后该OH_NativeImage指针会被赋值为空。

详细的接口说明请参考native_image。

开发步骤

以下步骤描述了如何使用NativeImage提供的Native API接口，创建OH_NativeImage实例作为消费者端，将数据内容更新到OpenGL外部纹理上。

添加动态链接库

CMakeLists.txt中添加以下lib。

libEGL.so
libGLESv3.so
libnative_image.so
libnative_window.so
libnative_buffer.so

头文件

#include <EGL/egl.h>
#include <EGL/eglext.h>
#include <GLES3/gl3.h>
#include <native_image/native_image.h>
#include <native_window/external_window.h>
#include <native_buffer/native_buffer.h>

初始化EGL环境。

这里提供一份初始化EGL环境的代码示例。

#include <iostream>
#include <string>
#include <EGL/egl.h>
#include <EGL/eglext.h>

using GetPlatformDisplayExt = PFNEGLGETPLATFORMDISPLAYEXTPROC;
constexpr const char *EGL_EXT_PLATFORM_WAYLAND = "EGL_EXT_platform_wayland";
constexpr const char *EGL_KHR_PLATFORM_WAYLAND = "EGL_KHR_platform_wayland";
constexpr int32_t EGL_CONTEXT_CLIENT_VERSION_NUM = 2;
constexpr char CHARACTER_WHITESPACE = ' ';
constexpr const char *CHARACTER_STRING_WHITESPACE = " ";
constexpr const char *EGL_GET_PLATFORM_DISPLAY_EXT = "eglGetPlatformDisplayEXT";
EGLContext eglContext_ = EGL_NO_CONTEXT;
EGLDisplay eglDisplay_ = EGL_NO_DISPLAY;
static inline EGLConfig config_;

// 检查egl扩展
static bool CheckEglExtension(const char *extensions, const char *extension) {
    size_t extlen = strlen(extension);
    const char *end = extensions + strlen(extensions);

    while (extensions < end) {
        size_t n = 0;
        if (*extensions == CHARACTER_WHITESPACE) {
            extensions++;
            continue;
        }
        n = strcspn(extensions, CHARACTER_STRING_WHITESPACE);
        if (n == extlen && strncmp(extension, extensions, n) == 0) {
            return true;
        }
        extensions += n;
    }
    return false;
}

// 获取当前的显示设备
static EGLDisplay GetPlatformEglDisplay(EGLenum platform, void *native_display, const EGLint *attrib_list) {
    static GetPlatformDisplayExt eglGetPlatformDisplayExt = NULL;

    if (!eglGetPlatformDisplayExt) {
        const char *extensions = eglQueryString(EGL_NO_DISPLAY, EGL_EXTENSIONS);
        if (extensions && (CheckEglExtension(extensions, EGL_EXT_PLATFORM_WAYLAND) ||
                           CheckEglExtension(extensions, EGL_KHR_PLATFORM_WAYLAND))) {
            eglGetPlatformDisplayExt = (GetPlatformDisplayExt)eglGetProcAddress(EGL_GET_PLATFORM_DISPLAY_EXT);
        }
    }

    if (eglGetPlatformDisplayExt) {
        return eglGetPlatformDisplayExt(platform, native_display, attrib_list);
    }

    return eglGetDisplay((EGLNativeDisplayType)native_display);
}

static void InitEGLEnv() {
    // 获取当前的显示设备
    eglDisplay_ = GetPlatformEglDisplay(EGL_PLATFORM_OHOS_KHR, EGL_DEFAULT_DISPLAY, NULL);
    if (eglDisplay_ == EGL_NO_DISPLAY) {
        std::cout << "Failed to create EGLDisplay gl errno : " << eglGetError() << std::endl;
    }

    EGLint major, minor;
    // 初始化EGLDisplay
    if (eglInitialize(eglDisplay_, &major, &minor) == EGL_FALSE) {
        std::cout << "Failed to initialize EGLDisplay" << std::endl;
    }

    // 绑定图形绘制的API为OpenGLES
    if (eglBindAPI(EGL_OPENGL_ES_API) == EGL_FALSE) {
        std::cout << "Failed to bind OpenGL ES API" << std::endl;
    }

    unsigned int ret;
    EGLint count;
    EGLint config_attribs[] = {EGL_SURFACE_TYPE,
                               EGL_WINDOW_BIT,
                               EGL_RED_SIZE,
                               8,
                               EGL_GREEN_SIZE,
                               8,
                               EGL_BLUE_SIZE,
                               8,
                               EGL_ALPHA_SIZE,
                               8,
                               EGL_RENDERABLE_TYPE,
                               EGL_OPENGL_ES3_BIT,
                               EGL_NONE};

    // 获取一个有效的系统配置信息
    ret = eglChooseConfig(eglDisplay_, config_attribs, &config_, 1, &count);
    if (!(ret && static_cast<unsigned int>(count) >= 1)) {
        std::cout << "Failed to eglChooseConfig" << std::endl;
    }

    static const EGLint context_attribs[] = {EGL_CONTEXT_CLIENT_VERSION, EGL_CONTEXT_CLIENT_VERSION_NUM, EGL_NONE};

    // 创建上下文
    eglContext_ = eglCreateContext(eglDisplay_, config_, EGL_NO_CONTEXT, context_attribs);
    if (eglContext_ == EGL_NO_CONTEXT) {
        std::cout << "Failed to create egl context %{public}x, error:" << eglGetError() << std::endl;
    }

    // 关联上下文
    eglMakeCurrent(eglDisplay_, EGL_NO_SURFACE, EGL_NO_SURFACE, eglContext_);

    // EGL环境初始化完成
    std::cout << "Create EGL context successfully, version" << major << "." << minor << std::endl;
}

创建OH_NativeImage实例。

// 创建 OpenGL 纹理
GLuint textureId;
glGenTextures(1, &textureId);
// 创建 NativeImage 实例，关联 OpenGL 纹理
OH_NativeImage* image = OH_NativeImage_Create(textureId, GL_TEXTURE_2D);

获取对应的数据生产者端NativeWindow。

// 获取生产者NativeWindow
OHNativeWindow* nativeWindow = OH_NativeImage_AcquireNativeWindow(image);

设置NativeWindow的宽高。

int code = SET_BUFFER_GEOMETRY;
int32_t width = 800;
int32_t height = 600;
int32_t ret = OH_NativeWindow_NativeWindowHandleOpt(nativeWindow, code, width, height);

将生产的内容写入NativeWindowBuffer。

从NativeWindow中获取NativeWindowBuffer。

OHNativeWindowBuffer *buffer = nullptr;
int fenceFd;
// 通过 OH_NativeWindow_NativeWindowRequestBuffer 获取 OHNativeWindowBuffer 实例
OH_NativeWindow_NativeWindowRequestBuffer(nativeWindow, &buffer, &fenceFd);
 
BufferHandle *handle = OH_NativeWindow_GetBufferHandleFromNative(buffer);

将生产的内容写入NativeWindowBuffer。

#include <sys/mman.h>
 
// 使用系统mmap接口拿到bufferHandle的内存虚拟地址
void *mappedAddr = mmap(handle->virAddr, handle->size, PROT_READ | PROT_WRITE, MAP_SHARED, handle->fd, 0);
if (mappedAddr == MAP_FAILED) {
    // mmap failed
}
static uint32_t value = 0x00;
value++;
uint32_t *pixel = static_cast<uint32_t *>(mappedAddr);
for (uint32_t x = 0; x < width; x++) {
    for (uint32_t y = 0; y < height; y++) {
        *pixel++ = value;
    }
}
// 内存使用完记得去掉内存映射
int result = munmap(mappedAddr, handle->size);
if (result == -1) {
    // munmap failed
}

将NativeWindowBuffer提交到NativeWindow。

// 设置刷新区域，如果Region中的Rect为nullptr,或者rectNumber为0，则认为NativeWindowBuffer全部有内容更改。
Region region{nullptr, 0};
// 通过OH_NativeWindow_NativeWindowFlushBuffer 提交给消费者使用，例如：显示在屏幕上。
OH_NativeWindow_NativeWindowFlushBuffer(nativeWindow, buffer, fenceFd, region);

用完需要销毁NativeWindow。

OH_NativeWindow_DestroyNativeWindow(nativeWindow);

更新内容到OpenGL纹理。

// 更新内容到OpenGL纹理。
ret = OH_NativeImage_UpdateSurfaceImage(image);
if (ret != 0) {
    std::cout << "OH_NativeImage_UpdateSurfaceImage failed" << std::endl;
}
// 获取最近调用OH_NativeImage_UpdateSurfaceImage的纹理图像的时间戳和变化矩阵。
int64_t timeStamp = OH_NativeImage_GetTimestamp(image);
float matrix[16];
ret = OH_NativeImage_GetTransformMatrix(image, matrix);
if (ret != 0) {
    std::cout << "OH_NativeImage_GetTransformMatrix failed" << std::endl;
}

解绑OpenGL纹理，绑定到新的外部纹理上。

// 将OH_NativeImage实例从当前OpenGL ES上下文分离
ret = OH_NativeImage_DetachContext(image);
if (ret != 0) {
    std::cout << "OH_NativeImage_DetachContext failed" << std::endl;
}
// 将OH_NativeImage实例附加到当前OpenGL ES上下文, 且该OpenGL ES纹理会绑定到 GL_TEXTURE_EXTERNAL_OES, 并通过OH_NativeImage进行更新
GLuint textureId2;
glGenTextures(1, &textureId2);
ret = OH_NativeImage_AttachContext(image, textureId2);

OH_NativeImage实例使用完需要销毁掉。

// 销毁OH_NativeImage实例
OH_NativeImage_Destroy(&image);