resize.c

/**
 * resize.c
 *
 * Computer Science 50
 * Problem Set 4
 *
 * resize a bmp
 */

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

#include "bmp.h"

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

    if (atoi(argv[1])<0 || atoi(argv[1])>100)
    {
        printf("please provide a positive integer smaller or equal to 100\n");
        return 5;
    }
    // define scale
    int scale = atoi(argv[1]);

    // remember filenames
    char* infile = argv[2];
    char* outfile = argv[3];

    // open input file
    FILE* inptr = fopen(infile, "r");
    if (inptr == NULL)
    {
        printf("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_inptr, bf_outptr;
    fread(&bf_inptr, sizeof(BITMAPFILEHEADER), 1, inptr);

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

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

    int *inptr_padding = malloc(sizeof(int));

    *inptr_padding = (4 - (bi_inptr.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;


    // updating the outfile's BITMAPINFOHEADER
    bi_outptr.biWidth = bi_inptr.biWidth * scale;
    bi_outptr.biHeight = bi_inptr.biHeight * scale;
    int padding =  (4 - (bi_outptr.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    bi_outptr.biSizeImage = ((bi_outptr.biWidth * sizeof(RGBTRIPLE)) + padding) * bi_outptr.biHeight;

    // updating the outfile's BITMAPFILEHEADER
    bf_outptr.bfSize = bi_outptr.biSizeImage + 54;



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

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

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

    // iterate over infile's scanlines
    for (int i = 0, biHeight = abs(bi_inptr.biHeight); i < biHeight; i++)
    {
        for (int m = 0; m<scale; m++)
        {
            // iterate over pixels in scanline
            for (int j = 0; j < bi_inptr.biWidth; j++)
            {
                    // temporary storage
                    RGBTRIPLE triple;

                    // read RGB triple from infile
                    fread(&triple, sizeof(RGBTRIPLE), 1, inptr);
                for (int k = 0; k<scale;k++)
                {

                    // write RGB triple to outfile
                    fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
                }
            }
            // padding in outfile
            for (int l = 0; l < padding; l++)
            {
                fputc(0x00, outptr);
            }
            if (m<(scale-1))
            {
            fseek(inptr, -(sizeof(RGBTRIPLE)*bi_inptr.biWidth), SEEK_CUR);
            }
        }

        // skip over padding, if any
        fseek(inptr, *inptr_padding, SEEK_CUR);

        // then add it back (to demonstrate how)
    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // free inptr_padding
    free(inptr_padding);

    // that's all folks
    return 0;
}