How to write a C Program/Code to Copies a BMP piece by piece in C Programming Language ?
Solution:
#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];
if (n < 1 || n > 100){
printf("N must be between 1 and 100\n");
return 1;
}
// 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;
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;
}
BITMAPINFOHEADER newbi;
newbi.biWidth = bi.biWidth * n;
newbi.biHeight = bi.biHeight * n;
BITMAPFILEHEADER newbf;
// determine padding for scanlines (old image)
int padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
// determine padding for scanlines (new image)
int newpadding = (4 - (newbi.biWidth * sizeof(RGBTRIPLE)) % 4) %4;
newbi.biSizeImage = (newbi.biWidth * sizeof(RGBTRIPLE) + newpadding) * abs(newbi.biHeight);
newbf.bfSize = newbi.biSizeImage + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
// write outfile's BITMAPFILEHEADER
fwrite(&newbf, sizeof(BITMAPFILEHEADER), 1, outptr);
// write outfile's BITMAPINFOHEADER
fwrite(&newbi, sizeof(BITMAPINFOHEADER), 1, outptr);
// iterate over infile's scanlines
for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++)
{
// how many lines
for (int l = 0; l < n; l++){
// 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);
for (int t = 0; t < n; t++){
// 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 < newpadding; k++)
{
fputc(0x00, outptr);
}
}
}
// close infile
fclose(inptr);
// close outfile
fclose(outptr);
// that's all folks
return 0;
}