short resize - r/cs50

/*HELPING ME FROM r/cs50? Thank you!
Main appears at line 91. Before that, typedef and structs.
Some important lines are: 138 and 173! (also in 145 the real action begins, all the other stuff from main until there are declarations, opening/reading files...that suff).
THANKS AGAIN!!*/


/**
 * Resizes a BMP piece by piece, just because.
 */

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

/**
 * Common Data Types
 *
 * The data types in this section are essentially aliases for C/C++
 * primitive data types.
 *
 * Adapted from https://msdn.microsoft.com/en-us/library/cc230309.aspx.
 * See http://en.wikipedia.org/wiki/Stdint.h for more on stdint.h.
 */
typedef uint8_t  BYTE;
typedef uint32_t DWORD;
typedef int32_t  LONG;
typedef uint16_t WORD;

/**
 * BITMAPFILEHEADER
 *
 * The BITMAPFILEHEADER structure contains information about the type, size,
 * and layout of a file that contains a DIB [device-independent bitmap].
 *
 * Adapted from https://msdn.microsoft.com/en-us/library/dd183374(v=vs.85).aspx.
 */
typedef struct
{
    WORD bfType;
    DWORD bfSize;
    WORD bfReserved1;
    WORD bfReserved2;
    DWORD bfOffBits;
} __attribute__((__packed__))
BITMAPFILEHEADER;

/**
 * BITMAPINFOHEADER
 *
 * The BITMAPINFOHEADER structure contains information about the
 * dimensions and color format of a DIB [device-independent bitmap].
 *
 * Adapted from https://msdn.microsoft.com/en-us/library/dd183376(v=vs.85).aspx.
 */
typedef struct
{
    DWORD biSize;
    LONG biWidth;
    LONG biHeight;
    WORD biPlanes;
    WORD biBitCount;
    DWORD biCompression;
    DWORD biSizeImage;
    LONG biXPelsPerMeter;
    LONG biYPelsPerMeter;
    DWORD biClrUsed;
    DWORD biClrImportant;
} __attribute__((__packed__))
BITMAPINFOHEADER;

/**
 * RGBTRIPLE
 *
 * This structure describes a color consisting of relative intensities of
 * red, green, and blue.
 *
 * Adapted from https://msdn.microsoft.com/en-us/library/dd162939(v=vs.85).aspx.
 */
typedef struct
{
    BYTE rgbtBlue;
    BYTE rgbtGreen;
    BYTE rgbtRed;
} __attribute__((__packed__))
RGBTRIPLE;
//
//
//
//
//
//
//
int main(int argc, char *argv[])
{
    // ensure proper usage
    if (argc != 4)
    {
        fprintf(stderr, "Usage: ./resize k infile outfile\n");
        return 1;
    }

    // remember filenames
    int factor = atoi(argv[1]);
    char *infile = argv[2];
    char *outfile = argv[3];

    // open input file
    FILE *inptr = fopen(infile, "r");
    // open output file
    FILE *outptr = fopen(outfile, "w");
    // read infile's BITMAPFILEHEADER
    BITMAPFILEHEADER bf;
    fread(&bf, sizeof(BITMAPFILEHEADER), 1, inptr);
    // read infile's BITMAPINFOHEADER
    BITMAPINFOHEADER bi;
    fread(&bi, sizeof(BITMAPINFOHEADER), 1, inptr);


    //increasing height and width by factor
    bi.biWidth *= factor;
    bi.biHeight *= factor;


    //calculating padding from new width
    int padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;

    bi.biSizeImage = ((sizeof(RGBTRIPLE) * bi.biWidth) + padding) * abs(bi.biHeight);
    bf.bfSize = bi.biSizeImage + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    // write outfile's BITMAPFILEHEADER
    fwrite(&bf, sizeof(BITMAPFILEHEADER), 1, outptr);
    // write outfile's BITMAPINFOHEADER
    fwrite(&bi, sizeof(BITMAPINFOHEADER), 1, outptr);




    // iterate over infile's scanlines
    for (int i = 0, biHeight = abs(bi.biHeight); i < (biHeight / factor); i++)
    {
        // to resize vertically
        for (int l = 0; l < factor; l++)
        {
            //iterate over pixels in scanlines
            for (int j = 0; j < (bi.biWidth / factor); 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), factor, outptr);
            }

            // then add it back (to demonstrate how)
            for (int k = 0; k < padding; k++)
            {
                fputc(0x00, outptr);
            }

            fseek(inptr, 0, SEEK_CUR);


            //in the offset down here, choosing between -3 and the division (which equals -3) returns different .bmp outputs.
            //set the cursor at the beginning of the line to rewrite it, for vertical resizing purposes.
            if (l < factor - 1)
            {
                fseek(inptr, /*-3*//*-(bi.biWidth / factor)*/, SEEK_CUR);

            }
        }
    }
    // close infile
    fclose(inptr);
    // close outfile
    fclose(outptr);
    // success
    return 0;
}