resize_less.c

/**
 * Copies a BMP piece by piece, just because.
 */

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

#include "bmp.h"

int main(int argc, char *argv[])
{
    // ensure proper usage
    if (argc != 4)
    {
        fprintf(stderr, "Usage: ./resize n infile outfile\n");
        return 1;
    }

    // remember filenames
    int n = atoi(argv[1]);
    char *infile = argv[2];
    char *outfile = argv[3];

    // open input file
    FILE *inptr = fopen(infile, "r");
    if (inptr == NULL)
    {
        fprintf(stderr, "Could not open %s.\n", infile);
        return 2;
    }

    // open output file
    FILE *outptr = fopen(outfile, "w");
    if (outptr == NULL)
    {
        fclose(inptr);
        fprintf(stderr, "Could not create %s.\n", outfile);
        return 3;
    }

    // read infile's BITMAPFILEHEADER
    BITMAPFILEHEADER bf;
    fread(&bf, sizeof(BITMAPFILEHEADER), 1, inptr);

    // read infile's BITMAPINFOHEADER
    BITMAPINFOHEADER bi;
    fread(&bi, sizeof(BITMAPINFOHEADER), 1, inptr);

    // ensure infile is (likely) a 24-bit uncompressed BMP 4.0
    if (bf.bfType != 0x4d42 || bf.bfOffBits != 54 || bi.biSize != 40 ||
        bi.biBitCount != 24 || bi.biCompression != 0)
    {
        fclose(outptr);
        fclose(inptr);
        fprintf(stderr, "Unsupported file format.\n");
        return 4;
    }

    // remember infile's width & length
    BITMAPINFOHEADER infile_bi;
    infile_bi.biWidth = bi.biWidth;
    infile_bi.biHeight = abs(bi.biHeight);

    // determine infile padding for scanlines
    int infile_padding = (4 - (infile_bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;

    // determine outfile width

    bi.biWidth *= n;

    // determine outfile padding for scalines
    int outfile_padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;

    //update outfile headers
    bi.biHeight *= n;
    bi.biSizeImage = ((sizeof(RGBTRIPLE) * bi.biWidth) + outfile_padding) * abs(bi.biHeight);
    bf.bfSize = bi.biSizeImage + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

    // write outfile's BITMAPFILEHEADER
    fwrite(&bf, sizeof(BITMAPFILEHEADER), 1, outptr);

    // write outfile's BITMAPINFOHEADER
    fwrite(&bi, sizeof(BITMAPINFOHEADER), 1, outptr);

    // iterate over infile's scanlines
    for (int i = 0; i < infile_bi.biHeight; i++)
    {
        // array of RGB tripples
        RGBTRIPLE RGB_array[bi.biWidth];

        // index of RGB_array
        int index = 0;

        // iterate over pixels in scanline
        for (int j = 0; j < infile_bi.biWidth; j++)
        {
            // temporary storage
            RGBTRIPLE triple;

            // read RGB triple from infile
            fread(&triple, sizeof(RGBTRIPLE), 1, inptr);

            // write RGB triple into RGB_array n times
            for (int k = 0; k < n; k++)
            {

                RGB_array[index] = triple;
                index++;

                // another sanity check xD
                if (index >= bi.biWidth)
                    break;

            }

        }

        for (int l = 0; l < n; l++)
        {

            // write RGB_array to outfile n times
            fwrite(RGB_array, sizeof(RGBTRIPLE), bi.biWidth, outptr);

            // then add the outfile padding back (to demonstrate how)
            for (int m = 0; m < outfile_padding; m++)
            {
                fputc(0x00, outptr);
            }

        }

        // skip over infile padding, if any
        fseek(inptr, infile_padding, SEEK_CUR);



    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // success
    return 0;
}