CS50 pset3 resize

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

int sizeOf();

int main(int argc, char *argv[])
{

    if (argc != 4)  // make sure input has 3 arguments
    {
        printf("Usage: ./resize f infile outfile\n");
        return (1);
    }

    double f = atof(argv[1]);
    if (f <= 0 || f > 100)
    {
        printf("First argument must be 0-100\n");
        return (1);
    }
    // remember filenames
    char *infile = argv[2];
    char *outfile = argv[3];
    //                              end of user input
    //----------------------------------------------------------

    // open input file
    FILE *inptr = fopen(infile, "r");

    if (inptr == NULL)
    {
        fclose(inptr);
        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);

    // 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;
    }

    // +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ here we start manipulating the image  ++++++++++++++
    // determine padding for scanlines - general formula
    int padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;

    //  Declare new HEADER FILE & INFO for the scaled file and initialize it with old picture value
    //  so we can manipulate it

    BITMAPFILEHEADER scaled_bf = bf;
    BITMAPINFOHEADER scaled_bi = bi;

    //  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ scaling the BitMapInfoHeader

    scaled_bi.biHeight *= f;
    scaled_bi.biWidth *= f;

     // after resizing bi.biwidth, we update the padding formula with the new bi.biwidth

    int scaled_Padding = (4 - (scaled_bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;

    // now that we have new Padding, we can change the sizeimage in the BITMAPINFOHEADER

    scaled_bi.biSizeImage = ((sizeof(RGBTRIPLE) * scaled_bi.biWidth) + scaled_Padding) * abs(scaled_bi.biHeight);

    //+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Scaling the BITMAPFILEHEADER

    scaled_bf.bfSize = scaled_bi.biSizeImage + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

    //  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++  Writing the new Headers of the Scaled File

    RGBTRIPLE scan[scaled_bi.biWidth];

    // write outfile's BITMAPFILEHEADER
    // determine padding for scanlines - general formula
    fwrite(&scaled_bf, sizeof(BITMAPFILEHEADER), 1, outptr);

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

//  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ resizing the pixels


    // iterate over ROW (the original picture)
    for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++)
    {
        // iterate over pixels in Lines of original Picture
        for (int j = 0; j < bi.biWidth; j++)
        {
            // temporary storage
            RGBTRIPLE triple;

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

            // write RGB triple to outfile
            fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr); // Here it duplicate every pixel f times
        }

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

        // then add it back (to demonstrate how)
        for (int k = 0; k < scaled_Padding; k++) //  here it adds the new padding if needed
        {
            fputc(0x00, outptr);
        }
    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // success
    return 0;

}  // main