#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stdlib.h>

struct _sBmpHeader
{
    char		bm[2];
    uint32_t	size;
    uint32_t	reserve;
    uint32_t	offset;
    uint32_t	header_size;
    uint32_t	width;
    uint32_t	height;
    uint16_t	planes;
    uint16_t	bpp;
    uint32_t	compression;
    uint32_t	bitmap_size;
    uint32_t	hres;
    uint32_t	vres;
    uint32_t	used;
    uint32_t	important;
}__attribute__ ((__packed__));

typedef struct _sBmpHeader sBmpHeader;

int main()
{
    char fn[258];
    char c;
    int32_t rate;
    int32_t originHeight, originWidth;
    FILE *SourceFile = NULL;
    FILE *ResultFile = NULL;

    puts("your file path?");
    fgets(fn, 256, stdin);
    while( strlen(fn)>256 )
    {
        puts("file path too long, plz retry");
        strcpy(fn, "");
        fgets(fn, 256, stdin);
    }

    if( fn[ strlen(fn) ] > 256)
        fn[256] =  '\0' ;
    else
        fn[ strlen(fn)-1 ] =  '\0' ;


    if( ( SourceFile = fopen( fn, "rb" ) ) == NULL )
    {
        printf( "sorry, file [%s] could not be opened!\n" ,fn);
        return 0;
    }

    rate = 1;
    puts("your downscale rate? (int )[2~10]");
    while( scanf("%d" ,&rate)!= 1 || rate > 10 || rate < 2)
    {
        puts("downscale rate error, plz retry");
        while( c = getchar()!='\n' )
            ;
    }

    SourceFile = fopen( "downscaled.bmp", "wb" );

    sBmpHeader	header;
    fread( &header, sizeof( header ), 1, SourceFile );
    originHeight = header.height;
    originWidth = header.width;
    header.height = originHeight / rate ;
    header.width = originWidth / rate ;
    fwrite( &header, sizeof( header ), 1, ResultFile );

    while( !feof( SourceFile ) )
    {
        uint8_t	original[ originHeight ][ originWidth ] = {0};
        uint8_t modified[ originHeight/rate ][ originWidth/rate ] = {0};

        for(size_t i = 0 ; i < rate ; i++)
        {
            size_t count = fread( original, 1, originWidth, SourceFile );
            for( size_t j = k = 0 ; j < originWidth ; j++)
            {
                modified[i][k] = modified[i][k] + original[i][j] ;
                if( (j+1) % rate == 0)
                    k++;
            }

        }






        for( size_t j = 0 ; j < originWidth/rate ; j++)
            modified[j] = modified[j]/ rate ;

        //fwrite( modified, count, 1, ResultFile );

    }


    fclose( SourceFile );
    puts("done, your file [downscaled.bmp] is ready");

    return 0;
}