Thread: Move file postion indicator to next line

I am trying to resize a bmp image by FACTOR times. I got the width resize working correctly but for the height I need to print each row of pixels or 'RGBTRIPLE' FACTOR number of times. I am pretty sure I have the fseek line in the right spot (marked here) I just don't know how many bytes to move it by I tried 1 I though 1 byte past the end would move the pointer to the next line but that did not work. This is for a class so please no code. Here is my code. Thanks for any help

Code:

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


#include "bmp.h"


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


    // resize by
    int FACTOR = 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);


    bi.biSizeImage *= FACTOR;
    bi.biWidth *= FACTOR;
    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;
    }


    // 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 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;


    // iterate over infile's scanlines
    for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++)
    {
      //  for (int j = 0; j < FACTOR; j++)
       // {
            // iterate over pixels in scanline
            for (int k = 0; k < bi.biWidth; k++)
            {
                // temporary storage
                RGBTRIPLE triple;


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


                for (int k = 0; k < FACTOR; k++)
                {
                    // 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 
            for (int l = 0; l < padding; l++)
            {
                fputc(0x00, outptr);
            }
         //   fseek (outptr, 1, SEEK_CUR); //here
       // }
    }


    // close infile
    fclose(inptr);


    // close outfile
    fclose(outptr);


    return 0;
}