screencap命令源码分析

//源码路径frameworks/base/cmds/screencap/screencap.cpp//编译配置文件，Android.bp代替了Android.mkframeworks/base/cmds/screencap/Android.bp

//cc_binary表示需要编译成二进制可执行文件cc_binary {     //name表示编译之后的名称     name: "screencap",     //srcs表示编译源文件     srcs: ["screencap.cpp"],     //shared_libs表示依赖了哪些动态库     shared_libs: [         "libcutils",         "libutils",         "libbinder",         "libhwui",         "libui",         "libgui",     ],     //cflags表示指定编译器的编译选项     cflags: [         "-Wall",         "-Werror",         "-Wunused",         "-Wunreachable-code",     ], }

int main(int argc, char** argv){    //获取系统的显示列表    std::optional<PhysicalDisplayId> displayId = SurfaceComposerClient::getInternalDisplayId();    if (!displayId) {        fprintf(stderr, "Failed to get token for internal displayn");        return 1;    }
    const char* pname = argv[0];    bool png = false;    int c;    //参数解析    while ((c = getopt(argc, argv, "phd:")) != -1) {        switch (c) {            case 'p':                //指定-p表示生成png图片                png = true;                break;            case 'd':                displayId = atoll(optarg);                break;            case '?':            case 'h':                usage(pname, *displayId);                return 1;        }    }    argc -= optind;    argv += optind;
    int fd = -1;    const char* fn = NULL;    if (argc == 0) {        fd = dup(STDOUT_FILENO);    } else if (argc == 1) {        fn = argv[0];        fd = open(fn, O_WRONLY | O_CREAT | O_TRUNC, 0664);        if (fd == -1) {            fprintf(stderr, "Error opening file: %s (%s)n", fn, strerror(errno));            return 1;        }        const int len = strlen(fn);        if (len >= 4 && 0 == strcmp(fn+len-4, ".png")) {            png = true;        }    }
    if (fd == -1) {        usage(pname, *displayId);        return 1;    }
    void const* mapbase = MAP_FAILED;    ssize_t mapsize = -1;
    void* base = NULL;    uint32_t w, s, h, f;    size_t size = 0;
    // setThreadPoolMaxThreadCount(0) actually tells the kernel it's    // not allowed to spawn any additional threads, but we still spawn    // a binder thread from userspace when we call startThreadPool().    // See b/36066697 for rationale    ProcessState::self()->setThreadPoolMaxThreadCount(0);    ProcessState::self()->startThreadPool();
    ui::Dataspace outDataspace;    sp<GraphicBuffer> outBuffer;    //使用ScreenshotClient屏幕截图操作    status_t result = ScreenshotClient::capture(*displayId, &outDataspace, &outBuffer);    if (result != NO_ERROR) {        close(fd);        return 1;    }
    result = outBuffer->lock(GraphicBuffer::USAGE_SW_READ_OFTEN, &base);
    if (base == nullptr || result != NO_ERROR) {        String8 reason;        if (result != NO_ERROR) {            reason.appendFormat(" Error Code: %d", result);        } else {            reason = "Failed to write to buffer";        }        fprintf(stderr, "Failed to take screenshot (%s)n", reason.c_str());        close(fd);        return 1;    }
    w = outBuffer->getWidth();    h = outBuffer->getHeight();    s = outBuffer->getStride();    f = outBuffer->getPixelFormat();    size = s * h * bytesPerPixel(f);
    if (png) {        //创建图片信息对象        const SkImageInfo info =            SkImageInfo::Make(w, h, flinger2skia(f), kPremul_SkAlphaType,                              dataSpaceToColorSpace(outDataspace));        SkPixmap pixmap(info, base, s * bytesPerPixel(f));        struct FDWStream final : public SkWStream {          size_t fBytesWritten = 0;          int fFd;          FDWStream(int f) : fFd(f) {}          size_t bytesWritten() const override { return fBytesWritten; }          bool write(const void* buffer, size_t size) override {            fBytesWritten += size;            return size == 0 || ::write(fFd, buffer, size) > 0;          }        } fdStream(fd);        //屏幕数据进行编码，这个地方传入的kPNG表示png图片格式编码        (void)SkEncodeImage(&fdStream, pixmap, SkEncodedImageFormat::kPNG, 100);        if (fn != NULL) {            //通知图片视频库更新            notifyMediaScanner(fn);        }    } else {        //如果没指定生成png，后面直接输出到终端了，一大堆乱码        uint32_t c = dataSpaceToInt(outDataspace);        write(fd, &w, 4);        write(fd, &h, 4);        write(fd, &f, 4);        write(fd, &c, 4);        size_t Bpp = bytesPerPixel(f);        for (size_t y=0 ; y<h ; y++) {            write(fd, base, w*Bpp);            base = (void *)((char *)base + s*Bpp);        }    }    close(fd);    if (mapbase != MAP_FAILED) {        munmap((void *)mapbase, mapsize);    }
    return 0;}

 static status_t notifyMediaScanner(const char* fileName) {      String8 cmd("am broadcast -a android.intent.action.MEDIA_SCANNER_SCAN_FILE -d file://");      cmd.append(fileName);      cmd.append(" > /dev/null");      int result = system(cmd.string());      if (result < 0) {          fprintf(stderr, "Unable to broadcast intent for media scanner.n");          return UNKNOWN_ERROR;      }      return NO_ERROR;  }

adb shell am broadcast -a android.intent.action.MEDIA_SCANNER_SCAN_FILE -d file://xxxx

enum class SkEncodedImageFormat {  #ifdef SK_BUILD_FOR_GOOGLE3      kUnknown,  #endif      kBMP,      kGIF,      kICO,      kJPEG,      kPNG,      kWBMP,      kWEBP,      kPKM,      kKTX,      kASTC,      kDNG,      kHEIF,  };