Function removePaddingBits

dependency/densecrf/examples/lodepng.cpp:4129–4154

}

static void removePaddingBits(unsigned char* out, const unsigned char* in,
                              size_t olinebits, size_t ilinebits, unsigned h)
{
    /*
     After filtering there are still padding bits if scanlines have non multiple of 8 bit amounts. They need
     to be removed (except at last scanline of (Adam7-reduced) image) before working with pure image buffers
     for the Adam7 code, the color convert code and the output to the user.
     in and out are allowed to be the same buffer, in may also be higher but still overlapping; in must
     have >= ilinebits*h bits, out must have >= olinebits*h bits, olinebits must be <= ilinebits
     also used to move bits after earlier such operations happened, e.g. in a sequence of reduced images from Adam7
     only useful if (ilinebits - olinebits) is a value in the range 1..7
     */
    unsigned y;
    size_t diff = ilinebits - olinebits;
    size_t ibp = 0, obp = 0; /*input and output bit pointers*/
    for(y = 0; y < h; ++y)
    {
        size_t x;
        for(x = 0; x < olinebits; ++x)
        {
            unsigned char bit = readBitFromReversedStream(&ibp, in);
            setBitOfReversedStream(&obp, out, bit);
        }
        ibp += diff;
    }
}

/*out must be buffer big enough to contain full image, and in must contain the full decompressed data from
 the IDAT chunks (with filter index bytes and possible padding bits)