resizeless.c

// Copies a BMP file

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

#include "bmp.h"


// Use debug50 if confused
// ToDo
// Tidy up
// Use Style50
// Watch remainder of Walkthrough



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

    // Create size factor from input

    int n = atoi(argv[1]);

    // Check n is greater than 1 and less than 100

    if (n < 1 || n > 100)
    {
        fprintf(stderr, "Usage: n needs to be positive number less than 100\n");
        return 1;
    }

    // remember filenames
    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;
    }

    // Save width and height (height saved as positive number)
    int width_save = bi.biWidth;

    int height_save = abs(bi.biHeight);

    int sizeimage_save = bi.biSizeImage;

    int size_save = bf.bfSize;

    // Padding save
    int padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;

    int padding_save = padding;

    printf("Old padding is %i\n", padding);

    // Change width and height based on n
    bi.biWidth = bi.biWidth * n;

    bi.biHeight = bi.biHeight * n;

    // Adjust new padding using new bi.biWidth
    padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;

    printf("New padding is %i\n", padding);

    // Create new Size Image and size
    bi.biSizeImage = ((sizeof(RGBTRIPLE) * bi.biWidth) + 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
    // Change the limit in this condition from new height to height save
    for (int i = 0; i < height_save; i++)
    {
        // iterate over pixels in scanline
        // Use width_save as the limit rather than bi.biWidth
        int loop_limit = n - 1;

        for (int x = 0; x < loop_limit; x++)
        {
            for (int j = 0; j < width_save; j++)
            {
                // 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 < n; l++)
                {
                    fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
                }
            }

            // Insert end of line padding
            for (int k = 0; k < padding; k++)
            {
                fputc(0x00, outptr);
            }

            // Create offset, old width in pixels converted to bytes
            int offset = -3 * width_save;

            // Move cursor
            fseek(inptr, offset, SEEK_CUR);
        }

        for (int j = 0; j < width_save; j++)
        {
            // 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 < n; l++)
            {
                fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
            }
        }

        // Insert end of line padding
        for (int k = 0; k < padding; k++)
        {
            fputc(0x00, outptr);
        }

        // final row write

        // skip over padding, if any
        // Replace padding in fseek with padding_save
        fseek(inptr, padding_save, SEEK_CUR);
    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // success
    return 0;
}