Formatted version of https://gist.github.com/thommyj/3403088

blobfind.c

#include <stdio.h>
#include <stdlib.h>

int main(int argc,char **argv)
{
   FILE *afile = NULL;
   FILE *bfile = NULL;

   unsigned char *bbuffer = NULL;

   int achar;
   int bsize;
   int acnt=0, bcnt=0, i;

   if(argc<3){
     printf("Usage: %s file1 file2\r\n Program tries to find file2 (binary) inside file1\r\n", argv[0]);
     return 1;
   }

   afile = fopen(argv[1], "rb");
   bfile = fopen(argv[2], "rb");

   if(afile == NULL || bfile == NULL){
      perror("Filename correct? ");
      goto shutdown;
   }

   fseek(bfile, 0L, SEEK_END);
   bsize = ftell(bfile);

   fseek(bfile, 0L, SEEK_SET);

   bbuffer = malloc(bsize);

   if(1 != fread(bbuffer,bsize,1,bfile)){
     perror("Unable to read file2");
     goto shutdown;
   }

   while(1)
     {
        achar = getc(afile);
        acnt++;

        if(achar == EOF){
          printf("Couldn't find file2 inside file1\r\n");
          goto shutdown;
        }

       if((unsigned char)achar == bbuffer[bcnt]){
         bcnt++;
       }else{
         bcnt = 0;
       }

      if(bcnt == bsize){
        printf("Found file2 at offset %d\r\n", acnt-bcnt);
        goto shutdown;
      }
   }

shutdown:
   if(afile)
     fclose(afile);
   if(bfile)
     fclose(bfile);
   if(bbuffer)
     free(bbuffer);

   return 0;
}

Compiled using zig cc

zig cc -o blobfind blobfind.c

$ ./blobfind  dump-embed-file balena.png 
Found file2 at offset 1131744

And then you can use dd to extract the file in question:

dd skip=1131744 bs=1 count=148 if=dump-embed-file of=output.png