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#include "CodecGrayCode.h"

#include <cmath>

#ifndef log2f

#define log2f(x) (log(x)/log(2.0))

#endif

using namespace std;

/*

 * The purpose of this function is to convert an unsigned

 * binary number to reflected binary Gray code.

 *

 * The operator >> is shift right. The operator ^ is exclusive or.

 * Source: http://en.wikipedia.org/wiki/Gray_code

 */

static unsigned int binaryToGray(unsigned int num) {

    return (num >> 1) ^ num;

}

/*

 * From Wikipedia: http://en.wikipedia.org/wiki/Gray_code

 * The purpose of this function is to convert a reflected binary

 * Gray code number to a binary number.

 */

static unsigned grayToBinary(unsigned num, unsigned numBits)

{

    for (unsigned shift = 1; shift < numBits; shift <<= 1){

        num ^= num >> shift;

    }

    return num;

}

/*

 * Function takes the decimal number

 * Function takes the Nth bit (1 to 31)

 * Return the value of Nth bit from decimal

 * Source: http://icfun.blogspot.com/2009/04/get-n-th-bit-value-of-any-integer.html

 */

static int get_bit(int decimal, int N){

    // Shifting the 1 for N-1 bits

    int constant = 1 << (N-1);

    // If the bit is set, return 1

    if( decimal & constant ){

        return 1;

    }

    // If the bit is not set, return 0

    return 0;

}

static inline int powi(int num, unsigned int exponent){

    // NOT EQUIVALENT TO pow()

    if(exponent == 0)

        return 1;

    float res = num;

    for(unsigned int i=0; i<exponent-1; i++)

        res *= num;

    return res;

}

// Encoder

EncoderGrayCode::EncoderGrayCode(unsigned int _screenCols, unsigned int _screenRows, CodecDir _dir) : Encoder(_screenCols, _screenRows, _dir){

    // Number of horizontal encoding patterns

    // Encode every pixel column

    Nhorz = ceilf(log2f((float)screenCols));

    // Number of vertical encoding patterns

    Nvert = ceilf(log2f((float)screenRows));

    // Set total pattern number

    if(dir & CodecDirHorizontal)

        this->N += Nhorz;

    if(dir & CodecDirVertical)

        this->N += Nvert;

    if(dir & CodecDirHorizontal){

        // Precompute horizontally encoding patterns

        for(unsigned int p=0; p<Nhorz; p++){

            cv::Mat patternP(1, screenCols, CV_8UC3);

            // Loop through columns in first row

            for(unsigned int j=0; j<screenCols; j++){

                unsigned int jGray = binaryToGray(j);

                // Amplitude of channels

                float amp = get_bit(jGray, Nhorz-p);

                patternP.at<cv::Vec3b>(0,j) = cv::Vec3b(255.0*amp,255.0*amp,255.0*amp);

            }

            patterns.push_back(patternP);

        }

    }

    if(dir & CodecDirVertical){

        // Precompute vertical encoding patterns

        for(unsigned int p=0; p<Nvert; p++){

            cv::Mat patternP(screenRows, 1, CV_8UC3);

            // Loop through rows in first column

            for(unsigned int i=0; i<screenRows; i++){

                unsigned int iGray = binaryToGray(i);

                // Amplitude of channels

                float amp = get_bit(iGray, Nvert-p); // Nvert-p-1?

                patternP.at<cv::Vec3b>(i,0) = cv::Vec3b(255.0*amp,255.0*amp,255.0*amp);

            }

            patterns.push_back(patternP);

        }

    }

}

cv::Mat EncoderGrayCode::getEncodingPattern(unsigned int depth){

    return patterns[depth];

}

// Decoder

DecoderGrayCode::DecoderGrayCode(unsigned int _screenCols, unsigned int _screenRows, CodecDir _dir) : Decoder(_screenCols, _screenRows, _dir){

    // Number of horizontal encoding patterns

    Nhorz = ceilf(log2f((float)screenCols));

    // Number of vertical encoding patterns

    Nvert = ceilf(log2f((float)screenRows));

    if(dir & CodecDirHorizontal)

        this->N += Nhorz;

    if(dir & CodecDirVertical)

        this->N += Nvert;

    frames.resize(N);

}

void DecoderGrayCode::setFrame(unsigned int depth, const cv::Mat frame){

    frames[depth] = frame;

}

void DecoderGrayCode::decodeFrames(cv::Mat &up, cv::Mat &vp, cv::Mat &mask, cv::Mat &shading){

    // Get shading (max) image

    shading = cv::Scalar(0);

    for(unsigned int f=0; f<frames.size(); f++){

        shading = cv::max(shading, frames[f]);

    }

    // Get min image

    cv::Mat minImage(shading.size(), CV_8U, cv::Scalar(255));

    for(unsigned int f=0; f<frames.size(); f++){

        minImage = cv::min(minImage, frames[f]);

    }

    // Threshold shading image for mask

    mask = (shading/minImage) > 2;

    // Binarize frames. TODO: subpixel interpolation.

    vector<cv::Mat> framesBinary(frames.size());

    for(unsigned int i=0; i<frames.size(); i++){

        // Foreground pixels 1, background 0

        //cv::threshold(frames[i], framesBinary[i], 80, 1, cv::THRESH_BINARY);

        framesBinary[i].create(frames[0].size(), CV_8U);

        framesBinary[i] = cv::abs(shading-frames[i]) < cv::abs(frames[i]-minImage);

        cv::threshold(framesBinary[i], framesBinary[i], 1, 1, cv::THRESH_BINARY);

    }

    if(dir & CodecDirHorizontal){

        vector<cv::Mat> framesHorz(framesBinary.begin(), framesBinary.begin()+Nhorz);

        // Construct up image.

        for(int i = 0; i < up.rows; i++){

            for(int j = 0; j < up.cols; j++){

                unsigned int enc = 0;

                for(unsigned int f=0; f<framesHorz.size(); f++){

                    // Gray decimal

                    enc += powi(2, Nhorz-f-1)*framesHorz[f].at<unsigned char>(i,j);

                }

                // Standard decimal

                enc = grayToBinary(enc, Nhorz);

                up.at<float>(i,j) = enc;

            }

        }

    }

    if(dir & CodecDirVertical){

        vector<cv::Mat> framesVert(framesBinary.end()-Nvert, framesBinary.end());

        // Construct vp image.

        for(int i = 0; i < vp.rows; i++){

            for(int j = 0; j < vp.cols; j++){

                unsigned int enc = 0;

                for(unsigned int f=0; f<framesVert.size(); f++){

                    // Gray decimal

                    enc += powi(2, Nvert-f-1)*framesVert[f].at<unsigned char>(i,j);

                }

                // Standard decimal

                enc = grayToBinary(enc, Nvert);

                vp.at<float>(i,j) = enc;

            }

        }

    }

}