在Android上用surface直接显示yuv数据

http://www.tuicool.com/articles/FviAZnu

研究了一段时间Android的surface系统，一直执着地认为所有在surface或者屏幕上显示的画面，必须要转换成RGB才能显示，yuv数据也要通过颜色空间转换成RGB才能显示。可最近在研究stagefright视频显示时发现，根本找不到omx解码后的yuv是怎么转换成RGB的代码，yuv数据在render之后就找不到去向了，可画面确确实实的显示出来了，这从此颠覆了yuv必须要转换成RGB才能显示的真理了。

稍微看一下AsomePlayer的代码，不难发现，视频的每一帧是通过调用了SoftwareRenderer来渲染显示的，我也尝试用利用SoftwareRenderer来直接render yuv数据显示，竟然成功了，这是一个很大的突破，以后可以直接丢yuv数据到surface显示，无需耗时耗效率的yuv转RGB了。

代码原创，贴出来与大家分享：Android 4.4平台 （其中yuv数据的地址可以从这里下载 点击打开链接 ，放到/mnt/sdcard目录）

#include<include/SoftwareRenderer.h>

#include <cutils/memory.h>

#include <unistd.h>
#include <utils/Log.h>

#include <binder/IPCThreadState.h>
#include <binder/ProcessState.h>
#include <binder/IServiceManager.h>

#include <gui/Surface.h>
#include <gui/SurfaceComposerClient.h>
#include <gui/ISurfaceComposer.h>
#include <ui/DisplayInfo.h>
#include <android/native_window.h>
#include <media/stagefright/MetaData.h>

using namespace android;

bool getYV12Data(const char *path,unsigned char * pYUVData,int size){
FILE *fp = fopen(path,"rb");
if(fp == NULL){
printf("read %s fail !!!!!!!!!!!!!!!!!!!\n",path);
return false;
}
fread(pYUVData,size,1,fp);
fclose(fp);
return true;
}

int main(void){
// set up the thread-pool
sp<ProcessState> proc(ProcessState::self());
ProcessState::self()->startThreadPool();

// create a client to surfaceflinger
sp<SurfaceComposerClient> client = new SurfaceComposerClient();
sp<IBinder> dtoken(SurfaceComposerClient::getBuiltInDisplay(
ISurfaceComposer::eDisplayIdMain));
DisplayInfo dinfo;
//获取屏幕的宽高等信息
status_t status = SurfaceComposerClient::getDisplayInfo(dtoken, &dinfo);
printf("w=%d,h=%d,xdpi=%f,ydpi=%f,fps=%f,ds=%f\n",
dinfo.w, dinfo.h, dinfo.xdpi, dinfo.ydpi, dinfo.fps, dinfo.density);
if (status)
return -1;
//创建surface,有些系统可能报错，dinfo.w和dinfo.h也可以写成固定值
sp<SurfaceControl> surfaceControl = client->createSurface(String8("showYUV"),
dinfo.w, dinfo.h, PIXEL_FORMAT_RGBA_8888, 0);

/*************************get yuv data from file;****************************************/
printf("[%s][%d]\n",__FILE__,__LINE__);
int width,height;
width = 320;
height = 240;
int size = width * height * 3/2;
unsigned char *data = new unsigned char[size];
char *path = "/mnt/sdcard/yuv_320_240.yuv";
getYV12Data(path,data,size);//get yuv data from file;
/*********************配置surface*******************************************************************/
SurfaceComposerClient::openGlobalTransaction();
surfaceControl->setLayer(100000);//设定Z坐标
surfaceControl->setPosition(100, 100);//以左上角为(0,0)设定显示位置
surfaceControl->setSize(width, height);//设定视频显示大小
SurfaceComposerClient::closeGlobalTransaction();
sp<Surface> surface = surfaceControl->getSurface();
printf("[%s][%d]\n",__FILE__,__LINE__);

/****************************************************************************************/
sp<MetaData> meta = new MetaData;
meta->setInt32(kKeyWidth, width);
meta->setInt32(kKeyHeight, height);
/*指定yuv格式，支持以下yuv格式
* OMX_COLOR_FormatYUV420Planar:
* OMX_TI_COLOR_FormatYUV420PackedSemiPlanar:
* HAL_PIXEL_FORMAT_YV12:
* 其他的貌似会转换成OMX_COLOR_Format16bitRGB565
*/
meta->setInt32(kKeyColorFormat, HAL_PIXEL_FORMAT_YV12);
//setRect不要也可以，我也不知道设置了有什么用，原理是什么，但是设置，参数一定要正确
meta->setRect(
kKeyCropRect,
0,//left
0,//top
width -1,//right
height -1);//bottom
printf("[%s][%d]\n",__FILE__,__LINE__);
SoftwareRenderer* sr = new SoftwareRenderer(surface,meta);//初始化
printf("[%s][%d]\n",__FILE__,__LINE__);
sr->render(data,size,NULL);//关键在这里，显示到屏幕上
delete[] data;

printf("[%s][%d]\n",__FILE__,__LINE__);

IPCThreadState::self()->joinThreadPool();//可以保证画面一直显示，否则瞬间消失
IPCThreadState::self()->stopProcess();
return 0;
}

LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)

LOCAL_SRC_FILES:= \
main.cpp

LOCAL_STATIC_LIBRARIES := \
libstagefright_color_conversion

LOCAL_SHARED_LIBRARIES := \
libcutils \
libutils \
libbinder \
libui \
libgui \
libstagefright\
libstagefright_foundation

LOCAL_C_INCLUDES := \
frameworks/native/include/media/openmax \
frameworks/av/media/libstagefright

LOCAL_MODULE:= showYUV

LOCAL_MODULE_TAGS := tests

include $(BUILD_EXECUTABLE)