Android用surface直接顯示yuv數據

研究了一段時間Android的surface系統，一直執著地認為所有在surface或者屏幕上顯示的畫面，必須要轉換成RGB才能顯示，yuv數據也要通過顏色空間轉換成RGB才能顯示。可最近在研究stagefright視頻顯示時發現，根本找不到omx解碼後的yuv是怎麼轉換成RGB的代碼，yuv數據在render之後就找不到去向了，可畫面確確實實的顯示出來了，這從此顛覆了yuv必須要轉換成RGB才能顯示的真理了。

稍微看一下AsomePlayer的代碼，不難發現，視頻的每一幀是通過調用了SoftwareRenderer來渲染顯示的，我也嘗試用利用SoftwareRenderer來直接render yuv數據顯示，竟然成功了，這是一個很大的突破，比如以後攝像頭采集到的yuv，可以直接丟yuv數據到surface顯示，無需耗時耗效率的yuv轉RGB了。

代碼原創，貼出來與大家分享：Android 4.4平台 （其中yuv數據的地址可以從這裡下載點擊打開鏈接，放到/mnt/sdcard目錄）

#include

#include 

#include 
#include 

#include 
#include 
#include 

#include 
#include 
#include 
#include 
#include 
#include 
 
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 proc(ProcessState::self());
    ProcessState::self()->startThreadPool();
	
	// create a client to surfaceflinger
    sp client = new SurfaceComposerClient();
	sp dtoken(SurfaceComposerClient::getBuiltInDisplay(
            ISurfaceComposer::eDisplayIdMain));
	DisplayInfo dinfo;
	//獲取屏幕的寬高等信息
    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;
	//創建surface,有些系統可能報錯，dinfo.w和dinfo.h也可以寫成固定值
    sp 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);//設定Z坐標
	surfaceControl->setPosition(100, 100);//以左上角為(0,0)設定顯示位置
	surfaceControl->setSize(width, height);//設定視頻顯示大小
    SurfaceComposerClient::closeGlobalTransaction();
	sp surface = surfaceControl->getSurface();
	printf("[%s][%d]\n",__FILE__,__LINE__);
	
/****************************************************************************************/	
	sp 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:
	 * 其他的貌似會轉換成OMX_COLOR_Format16bitRGB565
	 */
	meta->setInt32(kKeyColorFormat, HAL_PIXEL_FORMAT_YV12);
	//setRect不要也可以，我也不知道設置了有什麼用，原理是什麼，但是設置，參數一定要正確
	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);//關鍵在這裡，顯示到屏幕上
	delete[] data;
	
	printf("[%s][%d]\n",__FILE__,__LINE__);
	
	IPCThreadState::self()->joinThreadPool();//可以保證畫面一直顯示，否則瞬間消失
    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)