Step by Step solution about How to resolve the algorithm Bitmap/PPM conversion through a pipe step by step in the C programming language

The provided C code defines a function called print_jpg that converts an image to a JPEG format and then prints it. It also includes a main function that creates an image, fills it with a color, draws a line on it, prints it as a JPEG image, and then frees the allocated memory for the image.

Here's a breakdown of the code:

1. print_jpg Function:

   • This function takes an image struct and a qual parameter, which represents the desired JPEG quality level.
   • It creates a buffer buf to store a command.
   • It uses snprintf to format a command string into the buffer. The command is a call to the convert utility, which is a part of the ImageMagick suite. The command converts a PPM (Portable Pixmap) image to a JPEG image with the specified quality level.
   • It opens a pipe to the convert utility using popen.
   • It writes the PPM header information (width, height, and maximum color value) to the pipe.
   • It writes the pixel data from the img struct to the pipe.
   • It closes the pipe, which causes the convert utility to execute and produce the JPEG image.

2. main Function:

   • This function is the entry point of the program.
   • It creates an image struct using alloc_img.
   • It fills the image with a color using fill_img.
   • It draws a line on the image using draw_line.
   • It calls the print_jpg function to convert the image to JPEG and print it.
   • It frees the allocated memory for the image using free_img.

The code assumes that the convert utility is installed and available on the system. It also assumes that the imglib.h header file contains the definitions for the image struct and the functions used to manipulate the image.

/* interface */
void print_jpg(image img, int qual);


#define MAXCMDBUF 100
void print_jpg(image img, int qual)
{
   char buf[MAXCMDBUF];
   unsigned int n;
   FILE *pipe;
   
   snprintf(buf, MAXCMDBUF, "convert ppm:- -quality %d jpg:-", qual);
   pipe = popen(buf, "w");
   if ( pipe != NULL )
   {
           fprintf(pipe, "P6\n%d %d\n255\n", img->width, img->height);
           n = img->width * img->height;
           fwrite(img->buf, sizeof(pixel), n, pipe);
           pclose(pipe);
   }
}


#include "imglib.h"

int main()
{
      image img;
      
      img = alloc_img(100,100);
      fill_img(img, 50, 20, 200);
      draw_line(img, 0, 0, 80, 80, 255, 0, 0);
      print_jpg(img, 75);
      free_img(img);
}