How to download images for reduce network usage? - image

I am making android app that must show a lot of images from my REST API. I want to download images, and the next time check for images' name. If the image exists show them from the phone otherwise download from server.
Now I'm using Retrofit for my network requests and Glide for show images. But I have not good idea for solve this issue.
If needed I can change the network library or image loading library.
Thanks in advance

NOTE: This question might be too broad for the liking of S.O.
What you want to do is make what is known as a cache. The idea is that you have a unique identifier (often refered to as a key) for each object in the cache, such as an md5 sum of the image data, or original name + date of creation.
When you want to display an image, you first check if the image exists in the cache. If it exists simply return with the image from cache. if it does not exist, start the download and upon completion you insert the image into the cache.
Here is an example implementation that does what you want. I cannot vouch for it's quality because I never tried it.

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Riot API How to get summoner profile icon image

I found out i can get Summoner Icon image using this url:
https://ddragon.leagueoflegends.com/cdn/11.14.1/img/profileicon/934.png
The basic form of this is:
https://ddragon.leagueoflegends.com/cdn/{version}/img/profileicon/{profileIconId}.png
i know i can get the second value of {profileIconId} through Riot API but how do i know when i should update the version value? I don't want my app to crash when the version should be changed.
You should not be referencing ddragon for displaying icons or images. In fact, DataDragon specifically requests that you download the archive (.tgz) for each patch/version and host the assets locally or on your own CDN.
Websites like op.gg do this for all of the assets and host the images on their own CDN. They have to update their CDN every patch. You can automate updating the CDN using scripts, but for most small projects the work to automate this process may not be worth it.
Generally, it is considered rude to piggyback off of someone else's CDN without explicit permission to do so. Riot goes a step further and explicitly asks that you do not do this.
If someone is using the data dragon (ddragon) cdn, you can know the latest version looking at this json that they provide:
https://ddragon.leagueoflegends.com/api/versions.json
Just take the first element of the array and you are good to go without any scripting.

Thumbnail is broken when google drive is synced

I'm getting the thumbnail of a document using file.get API, which is stored the field thumbnailLink in the drive response. But after some time, I get only a broken image.
Could you please let me know the exact expiration time of the thumbnail, which determines the expiration time and how to extend it? We can download the thumbnail image, store it in the cloud and then use it. But since the users are many and the documents are many and the thumbnail varies based on the changes, so I don't think this would be a better approach. I wanted to know whether we have any workaround to fix this issue? Do we have anything to play with the google cache? If so, how to do? will this be a permanent solution
As stated in the documentation
Important: Thumbnails are invalidated each time the content of the file changes. When supplying thumbnails, it is important to upload new thumbnails each time the content is modified. Metadata changes do not invalidate thumbnails.
The google drive thumbnail image link changes the file is changed.
You will need to refresh it if the link is bad by doing a file.get or upload new thumbnail image metadata whenever you change the file.

How Should I store images - Codeigniter

I'm contemplating on how to store images in my new site.
Should I save the images directly to the database
OR
should I upload them to my server, while storing the path in my database?
Also, should it be the second choice, how does one retrieve the path of a file he uploaded previously?
You should definitely go with the second option as you can take advantage of the user's browser caching these images after the initial request. It also means your database wont be hit constantly for large files which is always a bad thing.
In CodeIgniter there are various parameters you can use to get the name / full file path to store in the database.
See http://ellislab.com/codeigniter%20/user-guide/libraries/file_uploading.html
Also take a look at this great SO question Storing Images in DB - Yea or Nay?
I tried CI's own libraries , its good but not best, Image moo solved all my problems, uploading, resize, crop etc..
http://www.matmoo.com/digital-dribble/codeigniter/image_moo/

openreadAsync vs Bitmap for image downloading from server

I have some image urls which I want to cache locally and save so that I don't need to make a web request again and again as needed.
Now, I am confused whether there is any significant benefit of using webclient's openreadasync method over bitmap for fetching the image for first time for saving it to IsolatedStorage.
For me, I think bitmap would be a better option as I would be able to get a event for progress.
This post gives good info on various image caching options.
http://blogs.msdn.com/b/swick/archive/2011/04/07/image-tips-for-windows-phone-7.aspx
Matt mentioned the fact that default image caching only works per session. So if you are implementing your own Image caching, then you will have to implement a image downloader for which the WebClient OpenReadAsync provides a way to store file locally
If you were't considering a local cache, UriSource would have been the choice.
If you want to cache images beyond the current application instance lifetime, have a look at http://blogs.msdn.com/b/delay/archive/2010/10/04/there-s-no-substitute-for-customer-feedback-improving-windows-phone-7-application-performance-now-a-bit-easier-with-lowprofileimageloader-and-deferredloadlistbox-updates.aspx which will show a way of saving the images to IsolatedStorage and then display it from there. This means you won't have to get it over the network each time the app is run.
If you're using this for lots of images be sure to manage the images you save as well so you don't fill up the disk with lots of old images you'll never need again.

what bits of info are stored in pinterest image urls?

The first bit before the _ is the id of the pin...what are the ZZtfjmGQ used for? I'm assuming the _c is probalby something to do with size.
http://media-cache-lt0.pinterest.com/upload/33284484717557666_HZtfjmFQ_c.jpg
I'm building an image upload service in node.js and was curious what other sites do to store the image.
Final images are served from a CDN, evident by the subdomain in the URL. The first bit, as you pointed out, is the id of the image, the second bit is a UID to get around cache limitations for image versions, and the last bit is image size.
A limitation of CDNs is the inability to process the image after upload. To get around this, my service uploads the files to my Nodejs server where I then serve the image back to the client. I use a jQuery script the user can use to crop the image which sends crop coordinates back to the server and I use ImageMagick to create the various sizes of the the uploaded image. You can obviously eliminate the crop step and just use aspect ratio's to automatically create the needed image sizes. I then upload the final images to the CDN for hosting to end users.
When a user needs to update a photo already in the CDN, the user uploads to nodejs server, images are processed and sized, the UID hash is updated and then uploaded to the CDN. If you want to keep things clean (and cut on CDN cost) you can delete the old "version" at this step as well. However, in my service I give the option to backtrack to an older version if needed.
The rest of the CRUD actions are pretty self explanatory. You can read a list of images available from the CDN using the ID (My service has a user id as well as an image id to allow more robust query operations) and deleting is as simple as identifying the image you want to delete.

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