resize.c

/**
 * copy.c
 *
 * Computer Science 50
 * Problem Set 4
 *
 * 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 || atoi(argv[1]) < 0 || atoi(argv[1]) > 100)
    {
        printf("Usage: ./resize n infile outfile\n");
        return 1;
    }
    
    // remember resize factor
    int n = 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;
    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;
    }
    
    // determine padding for infile scanlines
    int padding =  (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    
    // create outfile headers
    BITMAPFILEHEADER bf_outfile;
    BITMAPINFOHEADER bi_outfile;
    
    // update outfile headers
    bi_outfile.biWidth = bi.biWidth * n;
    bi_outfile.biHeight = abs(bi.biHeight) * n;
    
    // determine padding for outfile scanlines
    int outfile_padding =  (4 - (bi_outfile.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    
    // update outfile headers
    bi_outfile.biSizeImage = (bi_outfile.biWidth * sizeof(RGBTRIPLE) + outfile_padding) * bi_outfile.biHeight;
    bf_outfile.bfSize = bi_outfile.biSizeImage + sizeof(BITMAPINFOHEADER) + sizeof(BITMAPFILEHEADER);
    
    // write outfile's BITMAPFILEHEADER
    fwrite(&bf, sizeof(BITMAPFILEHEADER), 1, outptr);

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

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

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

                for (int k = 0; k < n; k++)
                {
                    // write RGB triple to outfile
                    fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
                }
                
                if (j != n - 1)
		        {
			        fseek(inptr, bi.biWidth * -1, SEEK_CUR);
		        }
            }
        }

        // skip over padding, if any
        fseek(inptr, padding, SEEK_CUR);
        
        if (i != 
    }
    
    else
    {
        // iterate over infile's scanlines
        for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++)
        {
            // iterate over pixels in scanline
            for (int j = 0; j < bi.biWidth; j++)
            {
                // temporary storage
                RGBTRIPLE triple;

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

                for (int k = 0; k < n; k++)
                {
                    // write RGB triple to outfile
                    fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
                }
            }
        }

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

        // then add it back (to demonstrate how)
        for (int k = 0; k < outfile_padding; k++)
        {
            fputc(0x00, outptr);
        }
        
        if (i != 
    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // that's all folks
    return 0;
}