Image saved from Fingerprint sensor seems corrupted

Question

I have been trying to put together code to actually save image from fingerprint sensors. I have already tried forums and this is my current code which saves file with correct file size but When i open the image, Its not image of fingerprint rather it looks like a corrupted image. Here is what it looks like.

My code is given below. Any help will be appreciated. I am new to windows development.

bool SaveBMP(BYTE* Buffer, int width, int height, long paddedsize, LPCTSTR bmpfile)
    {
        BITMAPFILEHEADER bmfh;
        BITMAPINFOHEADER info;
        memset(&bmfh, 0, sizeof(BITMAPFILEHEADER));
        memset(&info, 0, sizeof(BITMAPINFOHEADER));
        //Next we fill the file header with data:
        bmfh.bfType = 0x4d42;       // 0x4d42 = 'BM'
        bmfh.bfReserved1 = 0;
        bmfh.bfReserved2 = 0;
        bmfh.bfSize = sizeof(BITMAPFILEHEADER) +
            sizeof(BITMAPINFOHEADER) + paddedsize;
        bmfh.bfOffBits = 0x36;
        //and the info header:
        info.biSize = sizeof(BITMAPINFOHEADER);
        info.biWidth = width;
        info.biHeight = height;
        info.biPlanes = 1;

        info.biBitCount = 8;
        info.biCompression = BI_RGB;

        info.biSizeImage = 0;
        info.biXPelsPerMeter = 0x0ec4;
        info.biYPelsPerMeter = 0x0ec4;
        info.biClrUsed = 0;

        info.biClrImportant = 0;

        HANDLE file = CreateFile(bmpfile, GENERIC_WRITE, FILE_SHARE_READ,
            NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);

        //Now we write the file header and info header:
        unsigned long bwritten;
        if (WriteFile(file, &bmfh, sizeof(BITMAPFILEHEADER),
            &bwritten, NULL) == false)
        {
            CloseHandle(file);
            return false;
        }

        if (WriteFile(file, &info, sizeof(BITMAPINFOHEADER),
            &bwritten, NULL) == false)
        {
            CloseHandle(file);
            return false;
        }
        //and finally the image data:
        if (WriteFile(file, Buffer, paddedsize, &bwritten, NULL) == false)
        {
            CloseHandle(file);
            return false;
        }
        //Now we can close our function with
        CloseHandle(file);
        return true;
    }

    HRESULT CaptureSample()
    {
        HRESULT hr = S_OK;
        WINBIO_SESSION_HANDLE sessionHandle = NULL;
        WINBIO_UNIT_ID unitId = 0;
        WINBIO_REJECT_DETAIL rejectDetail = 0;
        PWINBIO_BIR sample = NULL;
        SIZE_T sampleSize = 0;

        // Connect to the system pool. 
        hr = WinBioOpenSession(
            WINBIO_TYPE_FINGERPRINT,    // Service provider
            WINBIO_POOL_SYSTEM,         // Pool type
            WINBIO_FLAG_RAW,            // Access: Capture raw data
            NULL,                       // Array of biometric unit IDs
            0,                          // Count of biometric unit IDs
            WINBIO_DB_DEFAULT,          // Default database
            &sessionHandle              // [out] Session handle
            );


        // Capture a biometric sample.
        wprintf_s(L"\n Calling WinBioCaptureSample - Swipe sensor...\n");
        hr = WinBioCaptureSample(
            sessionHandle,
            WINBIO_NO_PURPOSE_AVAILABLE,
            WINBIO_DATA_FLAG_RAW,
            &unitId,
            &sample,
            &sampleSize,
            &rejectDetail
            );

        wprintf_s(L"\n Swipe processed - Unit ID: %d\n", unitId);
        wprintf_s(L"\n Captured %d bytes.\n", sampleSize);

        PWINBIO_BIR_HEADER BirHeader = (PWINBIO_BIR_HEADER)(((PBYTE)sample) + sample->HeaderBlock.Offset);
        PWINBIO_BDB_ANSI_381_HEADER AnsiBdbHeader = (PWINBIO_BDB_ANSI_381_HEADER)(((PBYTE)sample) + sample->StandardDataBlock.Offset);
        PWINBIO_BDB_ANSI_381_RECORD AnsiBdbRecord = (PWINBIO_BDB_ANSI_381_RECORD)(((PBYTE)AnsiBdbHeader) + sizeof(WINBIO_BDB_ANSI_381_HEADER));
        PBYTE firstPixel = (PBYTE)((PBYTE)AnsiBdbRecord) + sizeof(WINBIO_BDB_ANSI_381_RECORD);
        SaveBMP(firstPixel, AnsiBdbRecord->HorizontalLineLength, AnsiBdbRecord->VerticalLineLength, AnsiBdbRecord->BlockLength, "D://test.bmp");

        wprintf_s(L"\n Press any key to exit.");
        _getch();
    }

Answer 1

IInspectable is correct, the corruption looks like it's coming from your implicit use of color tables:

info.biBitCount = 8;
info.biCompression = BI_RGB;

If your data is actually just 24-bit RGB, you can do info.biBitCount = 24; to render a valid bitmap. If it's lower (or higher) than that, then you'll need to do some conversion work. You can check AnsiBdbHeader->PixelDepth to confirm that it's the 8 bits per pixel that you expect.

It also looks like your passing AnsiBdbRecord->BlockLength to SaveBMP isn't quite right. The docs for this field say:

WINBIO_BDB_ANSI_381_RECORD structure
BlockLength
Contains the number of bytes in this structure plus the number of bytes of sample image data.

So you'll want to make sure to subtract sizeof(WINBIO_BDB_ANSI_381_RECORD) before passing it as your bitmap buffer size.

Side note, make sure you free the memory involved after the capture.

WinBioFree(sample);
WinBioCloseSession(sessionHandle);