Ttykuu

Windows 10 has an interesting feature where it will display "fun facts" and images on the lock screen. Occasionally, these images are something I would want to use for a background.

These images are stored in %LocalAppData%PackagesMicrosoft.Windows.ContentDeliveryManager_cw5n1h2txyewyLocalStateAssets.

As I wasn't certain if _cw5n1h2txyewy would be constant on the Microsoft.Windows.ContentDeliveryManager folder, I wanted to just search the %LocalAppData%Packages directory for Microsoft.Windows.ContentDeliveryManager*, and pull the first directory that matches that pattern.

Then, in that directory, I wanted to copy the images and read a "magic number" from each image, which can vary but determines the image type. In this case, I use the first 4 bytes as 0x89 0x50 0x4E 0x47 (or 0x89 then PNG), or bytes 6 through 9 as 0x4A 0x46 0x49 0x46 (JFIF) or 0x45 0x78 0x69 0x66 (Exif). The first condition would add the png extension, the second would add jpg.

The first function is my detect_file_type, which evaluates the file contents and determines what image type it is:

fn detect_file_type(data : &Vec<u8>) -> Option<String> 
 if data[0] == 0x89 && data[1] == 0x50 && data[2] == 0x4E && data[3] == 0x47 // ?PNG
 Some("png".to_string())
 else if data[6] == 0x4A && data[7] == 0x46 && data[8] == 0x49 && data[9] == 0x46 // JFIF
 Some("jpg".to_string())
 else if data[6] == 0x45 && data[7] == 0x78 && data[8] == 0x69 && data[9] == 0x66 // Exif
 Some("jpg".to_string())
 else 
 None
 

This is rather simple.

Next, I wanted my directory search function:

fn find_dir(search : &str, path : PathBuf) -> Option<PathBuf> 
 for entry in fs::read_dir(path).unwrap() 
 let path = entry.unwrap().path();
 if path.is_dir() 
 if path.file_name().unwrap().to_str().unwrap().starts_with(search) 
 return Some(path);
 
 
 
 return None;

Again, rather simple. We stuck to Option with both of these so that we can handle the error cases (if we need to).

And finally, we have all the critical work:

fn main() 
 let args = 
 App::new("Pull Windows Lock-Screen Pictures")
 .version("0.1")
 .about("Loads the images used for the main Windows 10 Lock-Screen backgrounds to the specified folder (or './out' if not specified).")
 .arg(Arg::with_name("destination")
 .help("The destination directory ('./out' by default)")
 .takes_value(true)
 .required(false))
 .get_matches();

 let my_dirs = Directories::with_prefix("windows_lock_screen_pictures", "Windows_Lock_Screen_Pictures").unwrap();
 let home = my_dirs.bin_home().parent().unwrap().parent().unwrap().join("Packages");
 let dir = find_dir("Microsoft.Windows.ContentDeliveryManager", home).unwrap().join("LocalState").join("Assets");

 for entry in fs::read_dir(dir).unwrap() 
 let path = entry.unwrap().path();
 if !path.is_dir() 
 let data = fs::read(&path).unwrap();
 let path_str = path.display().to_string();
 let file = path.file_name().unwrap().to_str().unwrap().to_string();

 let path_ext =
 match detect_file_type(&data) 
 Some(path_ext) => 
 let mut res = ".".to_string();
 res.push_str(&path_ext);
 res
 ,
 _ => "".to_string()
 ;

 let mut base_dest_dir = "".to_string();
 let mut default = std::env::current_dir().unwrap().to_str().unwrap().to_string();
 default.push_str("\out\");
 let dest_dir = args.value_of("destination").unwrap_or(&default);
 base_dest_dir.push_str(dest_dir);

 if !Path::new(&base_dest_dir).exists() 
 fs::create_dir(Path::new(&base_dest_dir)).expect("Could not create directory");
 

 base_dest_dir.push_str(&file);
 base_dest_dir.push_str(&path_ext);

 println!(" -> ", path_str, base_dest_dir);
 fs::write(Path::new(&base_dest_dir), data).expect("Could not write file");
 
 

Overall, we kept things rather small, but still allowed flexibility (and most of the safety we needed).

Our whole program is as follows:

extern crate clap;
extern crate dirs;

use std::fs::self;
use std::path::Path,PathBuf;
use clap::App,Arg;
use dirs::Directories;

fn detect_file_type(data : &Vec<u8>) -> Option<String> 
 if data[0] == 0x89 && data[1] == 0x50 && data[2] == 0x4E && data[3] == 0x47 // ?PNG
 Some("png".to_string())
 else if data[6] == 0x4A && data[7] == 0x46 && data[8] == 0x49 && data[9] == 0x46 // JFIF
 Some("jpg".to_string())
 else if data[6] == 0x45 && data[7] == 0x78 && data[8] == 0x69 && data[9] == 0x66 // Exif
 Some("jpg".to_string())
 else 
 None
 


fn find_dir(search : &str, path : PathBuf) -> Option<PathBuf> 
 for entry in fs::read_dir(path).unwrap() 
 let path = entry.unwrap().path();
 if path.is_dir() 
 if path.file_name().unwrap().to_str().unwrap().starts_with(search) 
 return Some(path);
 
 
 
 return None;


fn main() 
 let args = 
 App::new("Pull Windows Lock-Screen Pictures")
 .version("0.1")
 .about("Loads the images used for the main Windows 10 Lock-Screen backgrounds to the specified folder (or './out' if not specified).")
 .arg(Arg::with_name("destination")
 .help("The destination directory ('./out' by default)")
 .takes_value(true)
 .required(false))
 .get_matches();

 let my_dirs = Directories::with_prefix("windows_lock_screen_pictures", "Windows_Lock_Screen_Pictures").unwrap();
 let home = my_dirs.bin_home().parent().unwrap().parent().unwrap().join("Packages");
 let dir = find_dir("Microsoft.Windows.ContentDeliveryManager", home).unwrap().join("LocalState").join("Assets");

 for entry in fs::read_dir(dir).unwrap() 
 let path = entry.unwrap().path();
 if !path.is_dir() 
 let data = fs::read(&path).unwrap();
 let path_str = path.display().to_string();
 let file = path.file_name().unwrap().to_str().unwrap().to_string();

 let path_ext =
 match detect_file_type(&data) 
 Some(path_ext) => 
 let mut res = ".".to_string();
 res.push_str(&path_ext);
 res
 ,
 _ => "".to_string()
 ;

 let mut base_dest_dir = "".to_string();
 let mut default = std::env::current_dir().unwrap().to_str().unwrap().to_string();
 default.push_str("\out\");
 let dest_dir = args.value_of("destination").unwrap_or(&default);
 base_dest_dir.push_str(dest_dir);

 if !Path::new(&base_dest_dir).exists() 
 fs::create_dir(Path::new(&base_dest_dir)).expect("Could not create directory");
 

 base_dest_dir.push_str(&file);
 base_dest_dir.push_str(&path_ext);

 println!(" -> ", path_str, base_dest_dir);
 fs::write(Path::new(&base_dest_dir), data).expect("Could not write file");