C Program Copies a BMP piece by piece

C Program Copies a BMP piece by piece

How to write a C Program Copies a BMP piece by piece in C Programming Language ?


Solution:


/*Copies a BMP piece by piece*/
       
#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;
    }
    
    if (atoi(argv[1]) < 1 || atoi(argv[1]) > 100)
    {
        printf("size has to be between 1 and 100\n");
        return 1;
    }

    // remember filenames
    int multiple = atoi(argv[1]);
    char* infile = argv[2];
    char* outfile = argv[3];
    
    // open input file 
    FILE* inptr = fopen(infile, "r");
    if (inptr == NULL)
    {
        printf("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, bf_r;
    fread(&bf, sizeof(BITMAPFILEHEADER), 1, inptr);
    bf_r = bf;

    // read infile's BITMAPINFOHEADER
    BITMAPINFOHEADER bi, bi_r;
    fread(&bi, sizeof(BITMAPINFOHEADER), 1, inptr);
    bi_r = bi;
    

    // 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;
    }


    // resize header details
    bi_r.biWidth = bi.biWidth * multiple;
    bi_r.biHeight = bi.biHeight * multiple; 
    
     // determine padding for scanlines
    int padding =  (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    int r_padding = (4 - (bi_r.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
    
    // determine imageSize
    bi_r.biSizeImage = (bi_r.biWidth + r_padding) * abs(bi_r.biHeight) * sizeof(RGBTRIPLE); 
    bf_r.bfSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + bi_r.biSizeImage;
    
    // write outfile's BITMAPFILEHEADER
    fwrite(&bf_r, sizeof(BITMAPFILEHEADER), 1, outptr);
    
    // write outfile's BITMAPINFOHEADER
    fwrite(&bi_r, sizeof(BITMAPINFOHEADER), 1, outptr);

   
    // iterate over infile's scanlines
    for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++)
    {
        // iterate over pixels in scanline
        for (int j = 0; j < bi.biWidth; j++)
        {
            // temporary storage
            RGBTRIPLE triple;

            // read RGB triple from infile
            fread(&triple, sizeof(RGBTRIPLE), 1, inptr);
            
            // create temporary buffer for resized image
            int* buffer = malloc(bi_r.biSizeImage);
            
            // write each pixel multiple times
            for (int k = 0; k < multiple; k ++)
            {
            // 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; k++)
        {
            fputc(0x00, outptr);
        }
    }

    // close infile
    fclose(inptr);

    // close outfile
    fclose(outptr);

    // that's all folks
    return 0;
}


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