指针操作：【申请】、【释放】、【YUV2BGR】、【QT保存图像】

来源：互联网发布：高考必知文学常识编辑：程序博客网时间：2024/06/13 21:28

【指针的申请】：

 unsigned char *PRGB = new unsigned char[<span style="font-family:FangSong_GB2312;">640*480</span>*<span style="font-family:FangSong_GB2312;">3</span>];    //<span style="font-family:FangSong_GB2312;">申请640*480*3个字节的图像内存</span>//PRGB=(unsigned char*)malloc(<span style="font-family:FangSong_GB2312;">640*480</span>*<span style="font-family:FangSong_GB2312;">3</span>*sizeof(unsigned char));

malloc 和 new 都可以申请内存，二选一.

【指针的释放】：

delete []PRGB;    //释放数组指针PRGB =NULL;

【YUV2BGR】：

/***********************************************************************************@code     unsigned char *PRGB = new unsigned char[nLen*2];      //nLen 是 YUV图像的length         //因为YUV.length =Width*Height*3/2, BGR.length = Width*Height*3    //所以 BGR = YUV*2    v4lconvert_yuv420_to_bgr241__((const unsigned char*)pBuf, PRGB,nWidth, nHeight, 24);@encode***********************************************************************************/void Mythread::v4lconvert_yuv420_to_bgr241__(const unsigned char *src, unsigned char *dest,int width, int height, int yvu){    int i, j;    const unsigned char *ysrc = src;    const unsigned char *usrc, *vsrc;    if (yvu)    {        vsrc = src + width * height;        usrc = vsrc + (width * height) / 4;    } else {        usrc = src + width * height;        vsrc = usrc + (width * height) / 4;    }    for (i = 0; i < height; i++) {        for (j = 0; j < width; j += 2) {#if 1 /* fast slightly less accurate multiplication free code */            int u1 = (((*usrc - 128) << 7) +  (*usrc - 128)) >> 6;            int rg = (((*usrc - 128) << 1) +  (*usrc - 128) +                ((*vsrc - 128) << 2) + ((*vsrc - 128) << 1)) >> 3;            int v1 = (((*vsrc - 128) << 1) +  (*vsrc - 128)) >> 1;            *dest++ = CLIP(*ysrc + u1);            *dest++ = CLIP(*ysrc - rg);            *dest++ = CLIP(*ysrc + v1);            ysrc++;            *dest++ = CLIP(*ysrc + u1);            *dest++ = CLIP(*ysrc - rg);            *dest++ = CLIP(*ysrc + v1);#else            *dest++ = YUV2B(*ysrc, *usrc, *vsrc);            *dest++ = YUV2G(*ysrc, *usrc, *vsrc);            *dest++ = YUV2R(*ysrc, *usrc, *vsrc);            ysrc++;            *dest++ = YUV2B(*ysrc, *usrc, *vsrc);            *dest++ = YUV2G(*ysrc, *usrc, *vsrc);            *dest++ = YUV2R(*ysrc, *usrc, *vsrc);#endif            ysrc++;            usrc++;            vsrc++;        }        /* Rewind u and v for next line */        if (!(i & 1)) {            usrc -= width / 2;            vsrc -= width / 2;        }    }}

【从内存读取数据到Mat】：

Mat YUVDATA(Size(nWidth,nHeight),CV_8UC3,Scalar(0));memcpy(YUVDATA.data,PRGB,nWidth*nHeight*3);                //用memcpy将内存中的数据copy到Mat 中，然后<span style="font-family:FangSong_GB2312;">释放内存指针</span>delete []PRGB;PRGB =NULL;

【QT保存与读取图像】：

【保存成JPG图片】        QFile filebak(QString::fromStdString("/<span style="font-family:FangSong_GB2312;">yue</span>/info.jpg"));    filebak.open(QFile::WriteOnly);    filebak.write((const char*)pBuf, nLen);    filebak.close();<span style="font-family:FangSong_GB2312;">【读取图片】：    QPixmap pixmap("/yue/info.jpg");  </span>

【opencv解码JPG】：

<span style="font-size:18px;">    //因为JPG格式编码的图像，图像大小就等于它的Length    Mat temp_mat = Mat(1,nLen,CV_8UC1,pBuf);             </span><span style="font-size:18px;">    Mat jpgBuf = imdecode(temp_mat,CV_LOAD_IMAGE_COLOR);    Mat reSizeMat;    cv::resize(jpgBuf,reSizeMat,Size(iWidth,iHeight));    cv::cvtColor(reSizeMat,reSizeMat,CV_BGR2RGB);</span>

先申请一个一维的Mat来存jpg格式的数据（矩阵的长度就是图像的大小），然后imdecode解码，解码以后是BGR图像，需要转化成RGB

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