C# 无法显示具有正确颜色映射的 RAW16 灰度图像

Question

修改本link中提供的代码：

我写了这个：

    private void btnLoad_Click(object sender, EventArgs e)
    {
        if (System.IO.File.Exists(txtPicture.Text))
        {
            byte[] _data = System.IO.File.ReadAllBytes(txtPicture.Text);

            var _rgbData = Convert16BitGrayScaleToRgb16(_data, 160, 120);
            var _bmp = CreateBitmapFromBytes(_rgbData, 160, 120);

            pbFrame.Image = _bmp;
        }
    }

    private static void Convert16bitGSToRGB(UInt16 color, out byte red, out byte green, out byte blue)
    {
        red = (byte)(color & 0x31);
        green = (byte)((color & 0x7E0) >> 5);
        blue = (byte)((color & 0xF800) >> 11);
    }

    private static byte[] Convert16BitGrayScaleToRgb48(byte[] inBuffer, int width, int height)
    {
        int inBytesPerPixel = 2;
        int outBytesPerPixel = 6;

        byte[] outBuffer = new byte[width * height * outBytesPerPixel];
        int inStride = width * inBytesPerPixel;
        int outStride = width * outBytesPerPixel;

        // Step through the image by row
        for (int y = 0; y < height; y++)
        {
            // Step through the image by column
            for (int x = 0; x < width; x++)
            {
                // Get inbuffer index and outbuffer index
                int inIndex = (y * inStride) + (x * inBytesPerPixel);
                int outIndex = (y * outStride) + (x * outBytesPerPixel);

                byte hibyte = inBuffer[inIndex + 1];
                byte lobyte = inBuffer[inIndex];

                //R
                outBuffer[outIndex] = lobyte;
                outBuffer[outIndex + 1] = hibyte;

                //G
                outBuffer[outIndex + 2] = lobyte;
                outBuffer[outIndex + 3] = hibyte;

                //B
                outBuffer[outIndex + 4] = lobyte;
                outBuffer[outIndex + 5] = hibyte;
            }
        }
        return outBuffer;
    }

    private static byte[] Convert16BitGrayScaleToRgb16(byte[] inBuffer, int width, int height)
    {
        int inBytesPerPixel = 2;
        int outBytesPerPixel = 2;

        byte[] outBuffer = new byte[width * height * outBytesPerPixel];
        int inStride = width * inBytesPerPixel;
        int outStride = width * outBytesPerPixel;

        // Step through the image by row
        for (int y = 0; y < height; y++)
        {
            // Step through the image by column
            for (int x = 0; x < width; x++)
            {
                // Get inbuffer index and outbuffer index
                int inIndex = (y * inStride) + (x * inBytesPerPixel);
                int outIndex = (y * outStride) + (x * outBytesPerPixel);

                byte hibyte = inBuffer[inIndex];
                byte lobyte = inBuffer[inIndex+1];

                outBuffer[outIndex] = lobyte;
                outBuffer[outIndex+1] = hibyte;
            }
        }

        return outBuffer;
    }

    private static byte[] Convert16BitGrayScaleToRgb24(byte[] inBuffer, int width, int height)
    {
        int inBytesPerPixel = 2;
        int outBytesPerPixel = 3;

        byte[] outBuffer = new byte[width * height * outBytesPerPixel];
        int inStride = width * inBytesPerPixel;
        int outStride = width * outBytesPerPixel;

        for (int y = 0; y < height; y++)
        {
            for (int x = 0; x < width; x++)
            {
                int inIndex = (y * inStride) + (x * inBytesPerPixel);
                int outIndex = (y * outStride) + (x * outBytesPerPixel);

                byte hibyte = inBuffer[inIndex];
                byte lobyte = inBuffer[inIndex + 1];

                byte r, g, b;

                UInt16 color = (UInt16)(hibyte << 8 | lobyte);

                Convert16bitGSToRGB(color, out r, out g, out b);

                outBuffer[outIndex] = r;
                outBuffer[outIndex + 1] = g;
                outBuffer[outIndex + 2] = b;
            }
        }

        return outBuffer;
    }

    private static Bitmap CreateBitmapFromBytes(byte[] pixelValues, int width, int height)
    {
        //Create an image that will hold the image data

        Bitmap bmp = new Bitmap(width, height, PixelFormat.Format16bppRgb565);

        //Get a reference to the images pixel data
        Rectangle dimension = new Rectangle(0, 0, bmp.Width, bmp.Height);
        BitmapData picData = bmp.LockBits(dimension, ImageLockMode.ReadWrite, bmp.PixelFormat);
        IntPtr pixelStartAddress = picData.Scan0;

        //Copy the pixel data into the bitmap structure
        Marshal.Copy(pixelValues, 0, pixelStartAddress, pixelValues.Length);

        bmp.UnlockBits(picData);
        return bmp;
    }

但转换的结果仍然不是satisfying/correct。这是我应该得到的图片：

正在转换文件link在此处：

Example RAW16 picture file

这是使用 Convert16BitGrayScaleToRgb48:

的结果

这是使用 Convert16BitGrayScaleToRgb16 的结果：

这是使用 Convert16BitGrayScaleToRgb24:

的结果

很明显颜色重映射是错误的，但我无法理解问题出在哪里。

此外，我还发现 picturebox 并没有准确显示它存储的内容。上数第二张图片（Convert16BitGrayScaleToRgb48 结果）是图片框显示的内容，而下图是我将图片保存为 PNG 格式后得到的图片：

我认为 RAW16 灰度应该是指包含 16 位灰度值或在 565 或 555 地图上编码的 RGB 灰度值的 2 个字节。但是 none 这些假说似乎与真实的东西相符。

有人提示如何转换源文件中提供的值以获得与第一个一样的图片（使用 ImageJ 从同一来源获得）？

Answer 1

我使用 GIMP 找到了一个可能的提示。如果我通过这个应用程序加载原始文件（更改 .data and/or 中的扩展名强制将其加载为 RAW）并将其设置为 160x120 16bpp BigEndian 我得到一个几乎黑色的框架（！），但如果我改变压缩范围的水平，围绕唯一的小峰值（大约 12,0 黑色 - 13,0 白色）图像结果正确。更改字节顺序非常简单，可以稍微压缩动态范围，但我正在努力。

这次经历的第一个教训是“不要相信你的眼睛”:-)。

我努力的最终结果是这三种方法：

public static void GetMinMax(byte[] data, out UInt16 min, out UInt16 max, bool big_endian = true)
{
    if (big_endian)
        min = max = (UInt16)((data[0] << 8) | data[1]);
    else
        min = max = (UInt16)((data[1] << 8) | data[0]);

    for (int i = 0; i < (data.Length - 1); i += 2)
    {
        UInt16 _value;

        if (big_endian)
            _value = (UInt16)((data[i] << 8) | data[i + 1]);
        else
            _value = (UInt16)((data[i + 1] << 8) | data[i]);

        if (_value < min)
            min = _value;

        if (_value > max)
            max = _value;
    }
}

public static void CompressRange(byte MSB, byte LSB, UInt16 min, UInt16 max, out byte color, Polarity polarity)
{
    UInt16 _value = (UInt16)((MSB << 8) | LSB);

    _value -= min;

    switch (polarity)
    {
        case Polarity.BlackHot:
            _value = (UInt16)((_value * 255) / (max - min));
            _value = (UInt16)(255 - _value);
            break;

        default:
        case Polarity.WhiteHot:
            _value = (UInt16)((_value * 255) / (max - min));
            break;
    }

    color = (byte)(_value & 0xff);
}

public static byte[] Convert16BitGrayScaleToRgb24(byte[] inBuffer, int width, int height, UInt16 min, UInt16 max, bool big_endian = true, Polarity polarity = Polarity.WhiteHot)
{
    int inBytesPerPixel = 2;
    int outBytesPerPixel = 3;

    byte[] outBuffer = new byte[width * height * outBytesPerPixel];
    int inStride = width * inBytesPerPixel;
    int outStride = width * outBytesPerPixel;

    for (int y = 0; y < height; y++)
    {
        for (int x = 0; x < width; x++)
        {
            int inIndex = (y * inStride) + (x * inBytesPerPixel);
            int outIndex = (y * outStride) + (x * outBytesPerPixel);

            byte hibyte;
            byte lobyte;

            if (big_endian)
            {
                hibyte = inBuffer[inIndex];
                lobyte = inBuffer[inIndex + 1];
            }
            else
            {
                hibyte = inBuffer[inIndex + 1];
                lobyte = inBuffer[inIndex];
            }

            byte gray;

            CompressRange(hibyte, lobyte, min, max, out gray, polarity);

            outBuffer[outIndex] = gray;
            outBuffer[outIndex + 1] = gray;
            outBuffer[outIndex + 2] = gray;
        }
    }

    return outBuffer;
}

这些允许加载附加到原始问题的文件并将其显示在标准 WindowsForm PictureBox 上。使用 48bpp 格式会导致某些图形卡上的图像质量下降（至少我的是这样）。顺便说一句 GetMinMax 计算当前帧的最小最大值，而不考虑环境的历史记录。这意味着，如果您打算使用此功能来显示图片序列（就像我一样），则 FOV 中平均温度的强烈变化将使整个图像产生不同的曝光在丢失图片的一些细节。在这种情况下，我建议计算当前帧的最小值-最大值，但不要在 Convert16BitGrayScaleToRgb24 中使用它，而是对两个值使用 移动平均值 。

C# 无法显示具有正确颜色映射的 RAW16 灰度图像

C# unable to display RAW16 grayscale image with correct color mapping

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