// storage of bytes-to-write
RGBTRIPLE* line = malloc(bi.biWidth * sizeof(RGBTRIPLE));

// iterate over infile's scanlines
for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight / resize; i++)
{
    // iterate over pixels in scanline
    for (int j = 0; j < bi.biWidth / resize; j++)
    {
        // read RGB triple from infile
        // storage of bytes read
        RGBTRIPLE* pixel = malloc(sizeof(RGBTRIPLE));
        fread(pixel, sizeof(RGBTRIPLE), 1, inptr);
        fseek(inptr, padding, SEEK_CUR);

        //copying bytes read (stored in *pixel) to bytes-to-write (stored in *line)
        for (int k = 0; k < resize; k++)
        {
            //memcpy(line + (j * resize + k) * sizeof(RGBTRIPLE), pixel, sizeof(RGBTRIPLE));
            //*(line + (j * resize + k) * sizeof(RGBTRIPLE)) = *pixel;
        }

        free(pixel);
    }
  ...