resize.c, C (clang)

resize.c

// BMP-related data types based on Microsoft's own

#include <stdint.h>

// aliases for C/C++ primitive data types
// https://msdn.microsoft.com/en-us/library/cc230309.aspx
typedef uint8_t  BYTE;
typedef uint32_t DWORD;
typedef int32_t  LONG;
typedef uint16_t WORD;

// information about the type, size, and layout of a file
// 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;

// information about the dimensions and color format
// 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;

// relative intensities of red, green, and blue
// https://msdn.microsoft.com/en-us/library/dd162939(v=vs.85).aspx
typedef struct
{
    BYTE rgbtBlue;
    BYTE rgbtGreen;
    BYTE rgbtRed;
} __attribute__((__packed__))
RGBTRIPLE;
/**
 * copy.c
 *
 * Computer Science 50
 * Problem Set 4
 *
 * Copies a BMP piece by piece, just because.
 */
       
#include <stdio.h>
#include <stdlib.h>

#include "bmp.h"

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

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

//check the value of n
    if(n <= 0 || n > 100)
    {
        printf("Try to enter between 0 and 100.");
        return 2;
    }
    
    // open input file 
    FILE* inptr = fopen(infile, "r");
    if (inptr == NULL)
    {
        printf("Could not open %s.\n", infile);
        return 3;
    }

// open output file
    FILE* outptr = fopen(outfile, "w");
    if (outptr == NULL)
    {
        fclose(inptr);
        fprintf(stderr, "Could not create %s.\n", outfile);
        return 4;
    }

// 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 5;
    }
    
    // determine padding for scanlines
    int padding =  (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    
    // update header info for the out file
    BITMAPFILEHEADER bf_resize = bf;
    BITMAPINFOHEADER bi_resize = bi;
    bi_resize.biWidth = bi.biWidth * n;
    bi_resize.biHeight = bi.biHeight * n;
    
    // determine new padding after update header info
    int padding_resize = (4 - (bi_resize.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    
    // resize the image size
    bi_resize.biSizeImage = (bi_resize.biWidth * sizeof(RGBTRIPLE) + padding_resize) * abs(bi_resize.biHeight);
    bf_resize.bfSize = bi_resize.biSizeImage + 54;
    
    // write outfile's BITMAPFILEHEADER
    fwrite(&bf_resize, sizeof(BITMAPFILEHEADER), 1, outptr);

// write outfile's BITMAPINFOHEADER
    fwrite(&bi_resize, sizeof(BITMAPINFOHEADER), 1, outptr);
    
    // iterate over infile's scanlines
    for (int i = 0, biHeight = abs(bi_resize.biHeight); i < biHeight; i++)
    {
        // resize vertical
        for(int repeatVertical = 0; repeatVertical < n; repeatVertical++)
        {
            // set the inptr position
            if(repeatVertical != 0)
                fseek(inptr, -(bi.biWidth * 3 + padding), SEEK_CUR);
            
            // read each scanline, pixel by pixel
            for (int j = 0; j < bi_resize.biWidth; j++)
            {
                // temporary storage
                RGBTRIPLE triple;
                
                // read RGB triple from infile
                fread(&triple, sizeof(RGBTRIPLE), 1, inptr);
                
                // resize horizontal
                for(int repeatHorizontal = 0; repeatHorizontal < n; repeatHorizontal++)
                {
                    // 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 (to demonstrate how)
                for (int k = 0; k < padding_resize; k++)
                {
                    fputc(0x00, outptr);
                }
    }

// close infile
    fclose(inptr);

// close outfile
    fclose(outptr);

// that's all folks
    return 0;
}


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