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How do Image Loading Libraries like Coil or Glide do memory management?

I am new to Android development. My app has use case where I want to download and display images from Internet. I am using Kotlin to build App and decided to use Coil library as Image loading library. While using my application, user's action my trigger download of multiple images. How do these image loading libraries make sure that memory/cache/disk space doesn't fill up? Do these libraries clear/delete images that were downloaded during last use?

The answer is going to depend on the particular library. But in general, they download the images to a file, to serve as a disk cache. That disk cache generally is kept to some limit in terms of size, with files being deleted on an LRU (least recently used) basis. They may then do the same with in memory representations, keeping the last N megabytes worth of images cached in a pool, ejecting on an LRU basis when needed. Ejecting them from the cache may or may not remove them from memory entirely- it depends on if any other reference to the object is maintained by client code. Some libraries allow configurable behavior on this, by either allowing client code to set size limits or provide entire cache implementations.
It's still possible for space to fill up. Especially memory- if you have too many bitmaps open and use up all available heap, then you're going OOM no matter what the loading library does. What the loading library will do is prevent multiple network requests for the same image, and prevent you from having to do all the cache management by hand.

Android best way to load images from device storage

I am loading multiple images locally from devices storage. I am currently using Glide to load them. But Glide is very big library and it offers many features which I don't need at all, for ex. disk cache and loading from internet. Is there any better and more efficient library or another way to load images from devices storage?
The only functionality I need is memory bitmap cache, async loading from Uri and resizing just like in Glide.

You can use Picasso, its method count is ~700 compared to ~3200 of Glide, you can save lots of method count here.
I will recommend you do keep using image library, it does lots of cool stuff in the background, which requires lots of dev efforts.
Resizing of images according to view size
Caching in memory using LRU cache
Recycling of Bitmaps to free up heap once you are done with displaying
Disk cache, so that you can load faster on app restart OR eviction from LRU cache
Proven record of working on fragmented Android ecosystem
No need to take care of threads, thread pools
Also on top of if you are using Proguard (using minifyEnabled true in your build.gradle ) for code obfuscation, it will strip away methods which are not getting used in your apk

Android Glide alternate cache in memory or disk

I´m working in an App which does have images that are used quite often, however there are others download used only once.
Does Glide have any way for deciding on the fly which images should be stored only in Disk or only in memory?
As far as I´ve seen it does the cache depends on the configuration buy I´de like to be able to say by myself which ones should be in disk and which ones no.

You can use .diskCacheStrategy() to manually control whether and how an individual request is cached on disk and skipMemoryCache() to control whether an individual request is cached in memory.

Whether picasso supports image disk caching

Before I had worked on Volley and I have used the DiskLruCache [link] with Volley to cache images on disk.
Now I have been working with app that is using Picasso.
I would like to know whether Picasso supports disk caching.
If it supports how can I fix the cache size.
Which will be useful when loading images from remote with disk caching?

Picasso supports disk caching, and it's relying on the HTTP client for this.
If you're using it with OkHttp, the default size for the disk cache will be around 50 MB (2% of total space, max 50MB, min 5MB).
If this doesn't meet your needs, you can either implement your own disk cache or manually initialise the OkHttpDownloader with a larger disk cache size when you initialise your Picasso using the Picasso.Builder.
I would recommend the latter, it should look something like
new Picasso.Builder(context).downloader(new OkHttpDownloader(MAX_CACHE_SIZE)).build();

How to retrieve images from cache memory in picasso?

I am using picasso library for loading images .In default picasso, It uses internal cache memory for loading images.But as per my app configuration ,i have to use external cache memory(Cache on Disk).
so i used this code for Cache on Disk
File httpCacheDir = new File(getApplicationContext().getExternalCacheDir(),"http");
long httpCacheSize = 10 * 1024 * 1024; // 10 MiB
HttpResponseCache.install(httpCacheDir, httpCacheSize);}
Picasso is flexible. So now it caches images in external Sd card..
The caches is stored in sdcard/android/data/packagename/cache/http
The caches are stored in ".1" ,".0". formats
so i just opened them and changes into ".1" to ".jpg".it gives exact images what i need.
But how to do in programatically? but picasso itself caches my memory in to my app for loading image into imageview.but i have to save them into sdcard directly as images/set bitmap as wallpaper in offline mode?

You can supply your own Cache implementation when building your Picasso instance. This way you can provide extra methods that you can call to retrieve bitmaps directly from your memory cache. Use Picasso.Builder to provide your own implementation for it. When you use with() you are using a static singleton internal instance thats setup with most of the default values (most apps need the default values anyway.)
Keep a reference of your Cache implementation around and directly interact with it. Picasso is meant to handle the loading/decoding and caching for you but there is no reason you cant build around it.
If you are referring about the disk cache, then no Picasso does not support that at the moment. This is by design because the disk layer cache is done by the HTTP layer and makes no distinction about it.
You could however, change the path of the disk cache. If you are using OkHttpDownloader then supply a different file when you construct your Downloader. Similarly for UrlConnectionDownloader you could extend it and override the load() method.

Picasso does handle the caching in it and downloading also you just need to place it in your target Image view similar to Aquery
According to The Corner Square Engineering blog
picasso handle downloading caching in it self and give its handler to user to use it and place the image in image view