RLEDecompress.cs

private static void RLEDecompress(byte[] data, byte[] output, int count)
{
    // https://en.wikipedia.org/wiki/PackBits
    int dind = 0;
    int ind = 0;
    int len;
    byte val;

    while (ind < count)
    {
        len = data[dind++];

        // (1 + n) literal bytes of data
        // bin       sb   ub
        // 0000 0000 0    128
        // 0111 1111 127  127
        if (len < 128) // 0 ~ 127
        {
            while (len-- >= 0)
                output[ind++] = data[dind++];
        }
        // One byte of data, repeated (1 – n) times in the decompressed output
        // bin       sb   ub    not         +2           1-n
        // 1111 1111 -1   256   0000 0000   0000 0010    2
        // 1000 0001 -127 129   0111 1110   1000 0000    128
        else if (128 < len)
        {
            val = data[dind++];
            len = (len ^ 0xFF) + 2;
            while (len-- > 0)
                output[ind++] = val;
        }
    }
}