resize.c

/**
 * resize.c
 *
 * Jody W Moore
 *
 * Computer Science 50
 * Problem Set 5
 *
 * 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)
    {
        printf("Usage: ./resize n infile outfile\n");
        return 1;
    }
    if (!(argv[1] > 0))
    {
       printf("please enter a positive number\n");
    }
    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);

    // local variables for calculations
    int inputHeight = abs(bi.biHeight);
    int outputHeight = bi.biHeight * n;
    int inputWidth = bi.biWidth;
    int outputWidth = inputWidth * n;
    // determine padding for scanlines
    int inputPadding =  (4 - (inputWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    int outputPadding = (4 - (outputWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    // output variables
    int outputImageSize = (outputWidth * sizeof(RGBTRIPLE) + outputPadding) * abs(outputHeight);
    int outputBFSize = outputImageSize + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

    // 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;
    }
     // write outfile's BITMAPFILEHEADER and BITMAPINFOHEADER
     if ( n < 100)
     {
          bf.bfSize = outputBFSize;
          bi.biWidth = outputWidth;
          bi.biHeight = outputHeight;
          bi.biSizeImage = outputImageSize;
          fwrite(&bf, sizeof(BITMAPFILEHEADER), 1, outptr);
          fwrite(&bi, sizeof(BITMAPINFOHEADER), 1, outptr);
     }
    // for each row in the input
    for (int row = 0; row < inputHeight; row++)
    {
        // iterate over infile's scanlines repeat n times
        for (int scan = 0; scan < n; scan++)
        {

            // iterate over pixels in the row
            for (int rPix = 0; rPix < inputWidth; rPix++)
            {

                 // temporary storage
                 RGBTRIPLE triple ;
                 // read a pixel from infile
                 fread(&triple, sizeof(RGBTRIPLE), 1, inptr);
                 // write n copies of pixel
                 for (int wPix = 0; wPix < n ; wPix ++)
                 {
                        // write RGB triple to outfile
                      fwrite(&triple, sizeof(RGBTRIPLE),1, outptr);
                 }
            }
             for (int m = 0; m < outputPadding; m++)
            {
                fputc(0x00, outptr);
            }
            int seeker = n-1 * (inputWidth * sizeof(RGBTRIPLE));
            if ( scan == n-1)
            {
                fseek(inptr, inputPadding, SEEK_CUR);
            }
            else
            {
                fseek(inptr,seeker,SEEK_CUR);
            }

      }



    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // that's all folks
    return 0;
}