I am back again with another question about resize more. I feel like I am pretty close, but for some reason it is not resizing horizonally properly when the factor is larger than 0 (I haven't dabbled in shrinking yet). Here is my code:

// 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 factor infile outfile\n");
        return 1;
    }

    // remember filenames
    float factor = atof(argv[1]);
    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);
    BITMAPINFOHEADER newBi;
    BITMAPFILEHEADER newBf;
    newBf = bf;
    newBi = bi;
    newBi.biWidth = bi.biWidth * factor;
    newBi.biHeight = bi.biHeight * factor;

    // 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 scanlines
    int padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    int newPadding = (4 - (newBi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    newBi.biSizeImage = ((newBi.biWidth) * sizeof(RGBTRIPLE) + (newPadding)) * abs(newBi.biHeight);
    newBf.bfSize = (bf.bfSize - bi.biSizeImage) + newBi.biSizeImage;

    // Changes image size
    newBi.biSizeImage = (newBi.biHeight * sizeof(RGBTRIPLE) + newPadding) * abs(newBi.biHeight);

    // write outfile's BITMAPFILEHEADER
    fwrite(&newBf, sizeof(BITMAPFILEHEADER), 1, outptr);

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

     // 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);

            // Writes pixels horizontally
            for (int h = 0; h < factor; h++)
            {
                for (int w = 0; w < factor; w++)
                {
                    // write RGB triple to outfile
                    fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
                }
            }
        }

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

        printf("Padding needed: %i vs old padding %i\n", newPadding, padding);
        // then add it back (to demonstrate how)
        for (int k = 0; k < newPadding; k++)
        {
            fputc(0x00, outptr);
        }
    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // success
    return 0;
}