Bitmap/Read an image through a pipe

This task is the opposite of the PPM conversion through a pipe. In this task, using a delegate tool (like cjpeg, one of the netpbm package, or convert of the ImageMagick package) we read an image file and load it into the data storage type defined here. We can also use the code from Read ppm file, so that we can use PPM format like a (natural) bridge between the foreign image format and our simple data storage.

C

Works with: POSIX version .1-2001

Here I've used convert by ImageMagick. It is up to the program to understand the source file type; in this way, we can read theoretically any image format ImageMagick can handle. The get_ppm function defined in Read ppm file is used.

<lang c>image read_image(const char *name);</lang>

<lang c>#include "imglib.h"

define MAXCMDBUF 100
define MAXFILENAMELEN 256
define MAXFULLCMDBUF (MAXCMDBUF + MAXFILENAMELEN)

image read_image(const char *name) {

     FILE *pipe;
     char buf[MAXFULLCMDBUF];
     image im;
     
     FILE *test = fopen(name, "r");
     if ( test == NULL ) {
        fprintf(stderr, "cannot open file %s\n", name);
        return NULL;
     }
     fclose(test);
     
     snprintf(buf, MAXFULLCMDBUF, "convert \"%s\" ppm:-", name);
     pipe = popen(buf, "r");
     if ( pipe != NULL )
     {
          im = get_ppm(pipe);
          pclose(pipe);
          return im;
     }
     return NULL;

}</lang>

OCaml

The read_ppm function of the page read ppm file and used by the code below would need to be changed to take as parameter an input channel instead of the filename. <lang ocaml>let read_image ~filename =

 if not(Sys.file_exists filename)
 then failwith(Printf.sprintf "the file %s does not exist" filename);
 let cmd = Printf.sprintf "convert \"%s\" ppm:-" filename in
 let ic, oc = Unix.open_process cmd in
 let img = read_ppm ~ic in
 (img)

</lang>

Tcl

Works with: Tcl version 8.6

Library: Tk

<lang tcl>package require Tk

proc magickalReadImage {bufferImage fileName} {

   set f [open |[list convert [file normalize $fileName] ppm:-] "rb"]
   try {
       $bufferImage put [read $f] -format ppm
   } finally {
       close $f
   }

}</lang>