16位CT DICOM数据转换为8位

CT DICOM数据常用16位有符号数据存储，可用DCMTK对其进行解析。

解析方法：

    DcmFileFormat dfile;
    OFCondition status1;
    DcmMetaInfo *metainfo1;
         
    status1 = dfile.loadFile("F:\imageData\CT\CTA\DD0215\A3932225");
    status1 = dfile.loadFile("F:\imageData\CT\CTA\bianfengying\bianfengying009.dcm");
    status1 = dfile.loadFile("F:\imageData\CT\CTA\55\1.2.392.200036.9116.2.1220972159.1407127612.8906.1.26.dcm");
    status1 = dfile.loadFile("F:\imageData\CT\12390000\06379867");
    metainfo1 = dfile.getMetaInfo();
    DcmDataset *data = dfile.getDataset();

    DcmElement* element = NULL;
     data->findAndGetElement(DCM_PixelData, element);


    DcmElement* Redelementcolor = NULL;
    data->findAndGetElement(DCM_RedPaletteColorLookupTableData, Redelementcolor);
    DcmElement* Greenelementcolor = NULL;
    data->findAndGetElement(DCM_GreenPaletteColorLookupTableData, Greenelementcolor);
    DcmElement* Blueelementcolor = NULL;
    data->findAndGetElement(DCM_BluePaletteColorLookupTableData, Blueelementcolor);

    unsigned short row(0);
    data->findAndGetUint16(DCM_Rows, row);
    unsigned short column(0);
    data->findAndGetUint16(DCM_Columns, column);
    OFString frame;
    data->findAndGetOFString(DCM_NumberOfFrames, frame);

    OFString windowCenter;
    data->findAndGetOFString(DCM_WindowCenter, windowCenter);
    OFString windowWidth;
    data->findAndGetOFString(DCM_WindowWidth, windowWidth);

    int window_center = 100;
    int window_width = 700;
    window_center = atoi(windowCenter.c_str());
    window_width = atoi(windowWidth.c_str());
    //Uint8* uint8pixdata = nullptr;
    //element->getUint8Array(uint8pixdata);

    long count = row*column;// *atoi(frame.c_str());

    int m_bytecount = count * sizeof(Uint16);
    Uint16* uint16pixdata = nullptr;
    element->getUint16Array(uint16pixdata);

可看到，通过 element->getUint16Array(uint16pixdata)，获取得到16位无符号的raw数据。如果需要将其处理成8位数据，还需要进一步处理。

我的处理方式（不一定准确，供探讨）

1.将获取得到的无符号16位数据，转换为有符号16位数据

2.通过窗宽窗位算法，对数据进行压缩，得到处理后的16位有符号数据。（可参考https://blog.csdn.net/wu_uuww/article/details/6286048）

3.通过最大最小值算法，将16位数据压缩成8位无符号数据

Sint16 *Sint16PixData = new Sint16[count];
    for (int i = 0; i < count; i++)
    {
        if (uint16pixdata[i] > 20000)
        {
            Sint16PixData[i] = uint16pixdata[i] - 65536;
        }
        else
        {
            Sint16PixData[i] = uint16pixdata[i];
        }
    }

    int min2 = 0；
    int max = 0;



    min2 = (2 * window_center - window_width) / 2.0 + 0.5;
    max = (2 * window_center + window_width) / 2.0 + 0.5;


    Sint16 * sint16PixData2 = new  Sint16[count];
    unsigned char * uint8PixData = new unsigned char[count];



    for (int i = 0; i < count; i++)
    {
        Sint16PixData[i] = Sint16PixData[i];
        Sint16 temp = (Sint16PixData[i] - min2) * 255 / (max - min2) ;
        sint16PixData2[i] = temp;
    }

    int int16max = getMaxValue(sint16PixData2, count);
    int int16min = getMinValue(sint16PixData2, count);

    for (int i = 0; i < count; i++)
    {
        int temp = (sint16PixData2[i] - int16min) * 255  / (int16max - int16min);

        uint8PixData[i] = temp;
    }

处理前（16位）

处理后（8位）

上面数据有些偏移，还不确定是什么问题。

上述方法供探讨，谢谢！