pset4 resize(less) vertical

Question

My code seems only work for horizontal but not vertical. I have tried different for loops but nothing works. Any suggestions would be extremely helpful. Thank you.

// Copies a BMP file

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

#include "bmp.h"

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

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

    int n = atoi(argv[1]);
    {
        if(n <= 0 || n > 100)
        {
           fprintf(stderr, "Invalid size\n");
           return 2;
        }
    }


    // open input file
    FILE *inptr = fopen(infile, "r");
    if (inptr == NULL)
    {
        fprintf(stderr, "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;
    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 5;
    }

    int biwidthO = bi.biWidth;
    int biheightO = bi.biHeight;
    bi.biWidth = bi.biWidth * n;
    bi.biHeight = bi.biHeight * n;
    int Repadding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    bi.biSizeImage = ((sizeof(RGBTRIPLE) * bi.biWidth) + Repadding) * 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);

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


    // iterate over infile's scanlines

    for (int m = 0; m < n; m++)
    {
        for (int i = 0, biHeightO = abs(biheightO); i < biHeightO; i++)
        {
            // iterate over pixels in scanline
            for (int j = 0; j < biwidthO; j++)
            {
                // temporary storage
                RGBTRIPLE triple;

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

                for (int u = 0; u < n; u++)
                {
                    // 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 < Repadding; k++)
            {
                fputc(0x00, outptr);
            }
        }
    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // success
    return 0;
}

Answer 1

Looks like too many loops. Why is there an outer loop that processed the entire input file n times?

Most of the pieces are there, but reprocessing the entire file more than once won't accomplish anything useful. You should be thinking about how to reprocess each line n times before moving on to the next. That code is missing. Also, where should the input file pointer be set to in the input file while RE-processing each line?

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