resize.c

/**
 * copy.c
 *
 * 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: ./copy infile outfile\n");
        return 1;
    }
    

    // remember filenames
    int sizeChange = atoi(argv[1]);
    char* infile = argv[2];
    char* outfile = argv[3];
    if (sizeChange < 1 || sizeChange > 100)
    {
        printf("Invalid resizing parameter\n"); 
        return 2;
    }       
    
    // open input file 
    FILE* inptr = fopen(infile, "r");
    if (inptr == NULL)
    {
        printf("Could not open %s.\n", infile);
        return 3;
    }

    // open output file
    FILE* outptr = fopen(outfile, "w");
    if (outptr == NULL)
    {
        fclose(inptr);
        fprintf(stderr, "Could not create %s.\n", outfile);
        return 4;
    }

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

    // read infile's BITMAPINFOHEADER
    BITMAPINFOHEADER bi, biNew;
    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 5;
    }
    
    //change values in header files   
    bfNew=bf;
    biNew=bi;

    biNew.biWidth *=sizeChange;
    biNew.biHeight *=sizeChange;
    
    // determine padding for scanlines
    int padding =  (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    int newPadding =  (4 - (biNew.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    
    //use newPadding to determine new sizing
    biNew.biSizeImage = (biNew.biWidth*3+newPadding)*abs(biNew.biHeight);
    bfNew.bfSize = biNew.biSizeImage + bfNew.bfOffBits;
    
    // write outfile's BITMAPFILEHEADER
    fwrite(&bfNew, sizeof(BITMAPFILEHEADER), 1, outptr);

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


    long reCopy;
    // iterate over infile's scanlines
    for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++)
    {
        reCopy=ftell(inptr);
        for (int j=0; j<sizeChange; j++)
        {
            fseek(inptr, reCopy, SEEK_SET);
            for (int k = 0; k < bi.biWidth; k++)
            {
                
                // temporary storage
                RGBTRIPLE triple;

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

                // write RGB triple to outfile
                for (int l=0; l<sizeChange; l++)
                    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 m = 0; m < newPadding; m++)
            {
               fputc(0x00, outptr);
            }
        }
    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // that's all folks
    return 0;
}