Resize vertical help

Question

After looking at several similar questions, I still cannot figure out why my code is not working! here is my vertical (this is in the beginning of the outer loop):

        if(a <= n)
    {
        fseek(inptr, -(biWidth2 * (sizeof(RGBTRIPLE) + padding2)), SEEK_CUR);
        a++;
    }
    else
    {
        a = 0;
        b++;
        printf("line %i\n", b);
        printf("%li\n", ftell(inptr));
    }

EDIT:

I have changed the code to the following, but the program still cannot seem to run correctly:

long fgetpos(outptr, pos);
    // iterate over pixels in scanline
    for (int j = 0; j < n; j++)
    {
        long pos1 = ftell(outptr);
        if(pos != pos1)
        {
            fsetpos(inptr, pos);
        }
        ...

Answer 1

You're code is not quite clear to me. here is some pseudocode:

Approach #1:

for each scanline in original BMP
{
    // resize vertically
    repeat n times
    {
        ensure file position indicator is at the beginning of current scanline

        // resize horizontally
        for each RGBTRIPLE in current scanline
        {
            read an RGBTRIPLE
            write current RGBTRIPLE n times to new BMP
        }

        write new padding to new BMP
    }

    skip over old padding
}

Approach #2:

for each scanline in the original BMP
{
    create big enough array of RGBTRIPLEs named triples

    for each RGBTRIPLE in current scanline
    {
        read an RGBTRIPLE

        // resize horizontally
        append current RGBTRIPLE n times contiguously to triples 
    }

    // resize vertically
    repeat n times
    {
        write triples (whole array) to new BMP
        write new padding to new BMP
    }      

    skip the old padding
}

Hope that helps!