Display integer fft results from stdin as ascii chars using ncurses. Ugly but fast

ascii_fft_disp_curses.c

#include <stdio.h>
#include <errno.h>
#include <string.h>

// based in part on: https://www.linuxjournal.com/content/getting-started-ncurses
#include <curses.h>
#include <stdlib.h>

#define FFT_SIZE (256)
#define ABS(x) ( (x )< 0 ? -(x) : (x))

// pipe from: arecord -D plughw:1,0 -c 1 -V mono -f S16_LE -t wav -r 44100 tmp.out
const char* intensity_map = " .:-=+*#%@" ;
static  short fft_buf[FFT_SIZE] = {0};

int fft_size = 256 ;

short map( short x, short in_min, short in_max, short out_min, short out_max)
{
    return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

int choose_color(short mapped_val )
{
    switch( mapped_val)
    {
        case 0:
            return COLOR_BLACK ;

        case 1:
            return COLOR_RED ;

        case 2:
            return COLOR_GREEN ;

        case 3:
            return COLOR_YELLOW;

        case 4:
            return COLOR_BLUE ;

        case 5:
            return COLOR_MAGENTA;

        case 6:
            return COLOR_GREEN ;

        case 7:
            return COLOR_WHITE ;

        default:
            return COLOR_BLACK ;
        
    }
}

int main( ) 
{
    int maxlines = 20;
    int maxcols = FFT_SIZE / 2;

    /* initialize curses */
    initscr();
    start_color( ) ;
    cbreak();
    noecho();

    WINDOW *fft_win = newwin(50, FFT_SIZE / 2, 0, 0);

    wclear(fft_win);
    scrollok(fft_win, 1) ;

    
    init_pair(1, COLOR_RED, COLOR_BLACK);
    init_pair(2, COLOR_GREEN, COLOR_BLACK);
    init_pair(3, COLOR_YELLOW, COLOR_BLACK);
    init_pair(4, COLOR_BLUE, COLOR_BLACK);
    init_pair(5, COLOR_MAGENTA, COLOR_BLACK);
    init_pair(6, COLOR_CYAN, COLOR_BLACK);
    init_pair(7, COLOR_WHITE, COLOR_BLACK);
    init_pair(8, COLOR_BLACK, COLOR_BLACK) ;
    
    if (!freopen(NULL, "rb", stdin))
    {
        fprintf(stderr, "freopen failed. error: %s\n", strerror(errno));
        getch( ) ;
        endwin( ) ;
        return 1 ;
    }

    int scaled_value = 0 ;
    int color_number = 0 ;
    int x = 0 ;
    int y = 0 ;

    size_t n_read = fread( fft_buf, 1, FFT_SIZE, stdin) ;
    while( n_read )
    {
        for( int y = 0 ; y < FFT_SIZE / 2 ; y++)
        {
            scaled_value = map( ABS(fft_buf[y]), ( short) 0, (short) 100, (short) 0, (short) 7 );
            if( scaled_value > 7)
            {
                scaled_value = 7 ;
            }

            color_number = choose_color(scaled_value) ;
            wattron( fft_win, COLOR_PAIR(color_number));
            waddch( fft_win, intensity_map[scaled_value]) ;
            wattroff( fft_win, COLOR_PAIR(8));
        }
        wrefresh( fft_win) ;
        
        n_read = fread( fft_buf, 1, FFT_SIZE, stdin) ;
        //scroll(fft_win) ;     
    }
    
    wrefresh(fft_win) ;

    endwin( ) ;
    return 0 ;

}