#include <math.h>
#include <utils2d.h>

static const double gammaval = 2.2;

/**
 * Returns a nonlinear R'G'B' channel value in 0-1 from a linear RGB
 * channel value in 0-1.
 */
double linear_to_nonlinear_rgb( double val )
{
    return pow( val, 1.0 / gammaval );
}

/**
 * Returns a linear RGB channel value in 0-1 from a nonlinear R'G'B'
 * channel value in 0-1.
 */
double nonlinear_to_linear_rgb( double val )
{
    return pow( val, gammaval );
}

void outputRgb24Scanline( unsigned char *output, Pixel *scanline, int w )
{
    for(; w; w-- ) {
        double r = scanline->r;
        double g = scanline->g;
        double b = scanline->b;

        if( r > 1.0 ) r = 1.0; if( r < 0.0 ) r = 0.0;
        if( g > 1.0 ) g = 1.0; if( g < 0.0 ) g = 0.0;
        if( b > 1.0 ) b = 1.0; if( b < 0.0 ) b = 0.0;

        r = ( linear_to_nonlinear_rgb( r ) * 255.0 ) + 0.5;
        g = ( linear_to_nonlinear_rgb( g ) * 255.0 ) + 0.5;
        b = ( linear_to_nonlinear_rgb( b ) * 255.0 ) + 0.5;

        *output++ = (unsigned char) r;
        *output++ = (unsigned char) g;
        *output++ = (unsigned char) b;
        scanline++;
    }
}

void outputRgb24ScanlineDownsample2( unsigned char *output,
                                     Pixel *top, Pixel *bot, int inw )
{
    int w = inw - 1;

    for(; w; w-- ) {
        double r = ( top->r + (top + 1)->r + bot->r + (bot + 1)->r ) / 4.0;
        double g = ( top->g + (top + 1)->g + bot->g + (bot + 1)->g ) / 4.0;
        double b = ( top->b + (top + 1)->b + bot->b + (bot + 1)->b ) / 4.0;

        if( r > 1.0 ) r = 1.0; if( r < 0.0 ) r = 0.0;
        if( g > 1.0 ) g = 1.0; if( g < 0.0 ) g = 0.0;
        if( b > 1.0 ) b = 1.0; if( b < 0.0 ) b = 0.0;

        r = ( linear_to_nonlinear_rgb( r ) * 255.0 ) + 0.5;
        g = ( linear_to_nonlinear_rgb( g ) * 255.0 ) + 0.5;
        b = ( linear_to_nonlinear_rgb( b ) * 255.0 ) + 0.5;

        *output++ = (unsigned char) r;
        *output++ = (unsigned char) g;
        *output++ = (unsigned char) b;
        top++;
        bot++;
    }
}