Part of the process used in my app involves taking a photo (done with Capture.capturePhoto()). The photo is then resized to a small square of 200px and finally sent to a server.
I am able to delete the resized image with FileSystemStorage.delete() however the initial photo taken with Capture.capturePhoto() cannot be deleted because of the app being sand boxed (as described in this SO question )
This can be embarrassing for the user because these photos are polluting their gallery (the photos have no value for the user).
As deleting the initial photo is not possible, I was wondering if I could force the Captured photo to be stored in cache so that it gets automatically removed by the OS.
Maybe this question could be a solution for Android but I would prefer to avoid having to go native?
Consequently is it possible with Codename one to take a photo that will only be temporary and be deleted automatically ?
Thanks a lot,
Cheers
We try to delete the file automatically but since the OS takes the photo some platforms just stick it in the gallery and there isn't much we can do there. It's literally a matter of "this works on Android device A and fails on Android device B".
Apps like snapchat etc. don't use the device camera app but instead use the low level camera API's which are more complex and flaky. At this time we don't map these API's in Codename One so if you need something with lower level control you will need to use native interfaces. This is a non-trivial API though.
Related
I have a react app that has many image references ( tags <img src=... /> and css background:url(...)) type.
These images are hosted on Azure Storage.
To speed up my App loading time on various devices (desktops and mobile), I need to resize these images before they hit the client, ie, on the server somewhere.
So far, I can think of the following options:
Pick each image, and produce multiple versions of them for various standard device sizes. Then, pick up each <img src=... /> tag, and, using JS alter the image name, such that the right size of image gets served. This will not work with css.
Use Azure CDN to automatically resize images. I was hoping that resizing would happen automatically, as the CDN portal retrieves the user-agent from the device. Does anyone know if this is true?
Serve images through an Azure function, resizing them on the fly (as suggested here)
Can someone suggest other options they can think of, or a pros / con of the above.
Since you're using javascript, use the window tag. For browsers, the window tab measures the resolution of the browser and you can set the height and width of your image to window.innerHeight and window.innerWidth. There are multiple other ways to do this but this is the easiest and most optimised if your coding project needs to be efficient with the least lines of code necessary.
More info about the window object here : https://www.w3schools.com/js/js_window.asp
P.S. this is only a solution for desktop, for mobile you can use screen.width, screen.height. This might not work on desktop but on a macOS Big Sur device it works, I tried it (This might be because macOS Big Sur is like a mobile optimised interface given that you can even run iOS apps on it but we don't know unless we try). That might be a better option as it is most likely common across all your devices.
More info about the screen object here : https://www.tutorialrepublic.com/faq/how-to-detect-screen-resolution-with-javascript.php
On the off-chance that none of them are common across all of your target devices, try making a detector program with which you can detect the device type and store that in a variable. Then create 2 if statements saying
if(deviceType = iOS){
<img src=..., screen.width, screen.height/>
}else if(deviceType = Windows){
<img src=..., window.innerWidth, window.innerHeight/>
}
Obviously this code won't work but it's just there to show you the flow where you can sort of understand what I meant. You need to integrate it your own way but this was just a way to make it easier as many times people mention that my answers are not easy to understand, just as a safety measure.
The best part of these options is that instead of remade copies of the image itself, this will resize the one, which saves storage space and eliminates the chance of the user using an unexpected display output like a 49" Samsung Odyssey G9 monitor where the resolution is extremely far from what you might have expected and resized. This also means you don't have to create a separate file just to make image resizing code, just the one to detect the OS (not necessary if the screen object works) which would've already been done since this is Azure we're talking about and they always detect their user base.
If you have any queries, please reply back.
Good luck!
I am planning to develop a hybrid mobile app using ionic. One of the features i need is offline google map. Is there a way how to do it?
It depends on the requirements of your application whether this will be possible. Are your users on "modern" devices A.K.A is HTML5 fully supported? Do your users need to view/edit the map globally, or just in a specific area? Does the map really need to be provided by google? I'll address some issues below to point you in possible takes on this problem.
Do you really need google maps? (Most optimal scenerio)
First of, do you really need google maps? Also relevant: how far do your users need to zoom their maps? If it can be any maps, and zooming is not really of high priority (if it is, including all map tiles will make the app eat all storage), you could probably use map-tiles as a packaged part of your app, and display them with a library like http://leafletjs.com/. The library is well documented, and provides a map-interface for a variety of map-providers. It will be do-able to configure this to use your own local map-tiles. You could include map-tiles for multiple zoom levels if necessary, and limit the min/max zoom-levels to the tiles you actually have available. This will make your maps work offline.
I can't or don't wan't to provide my own tiles make sure that you really looked into the option, there is systems out there that provide map-tiles you could use (check https://www.mapbox.com/ for example)
Okay, so you really don't want to do what I suggested. What are the options now? Javascript mapping-solutions typically render tiles based on the location of the map you want to see and the zooming level. These tiles are requested to the tile-provider. I do not know how to implement this for google exactly, you might need some research on this - I'll try to help you see a direction. There will be requests to get the tiles from the servers. I checked with http://maps.google.com what images are loaded when trying to navigate the map: (example (click)). Find out what url's are used in your situation, we will need these kind of url's later (just inspect the network tab in your browser console and see which requests are made when scrolling in your map). When we only need our users to work in a certain area when offline we could use service workers to cache the responses of these requests when we are online, and serve those caches when we are offline. Read more on service workers here (click).
Advantage: Real offline map-functionality for any tile you visited before (as long as your cache wasn't overflown, depending on your implementation of the service workers, and for service-worker supported browsers/devices).
Disadvantages: No support for tiles that were never put in the cache (AKA: never seen before). Another one: this will only work for devices that support service workers. Might be an option in situations where you either don't care about users using "older" devices, or where you can control the user's device choices. Note that using crosswalk could ease your developing efforts here, since you only have to consider one browser-runtime then: but crosswalk also doesn't support older devices.
However: This solution could be fine for people that will need to work in a specific area, which might be true for the case provided by #vipul-r If you or your users know in advance where they need their maps to work, you can instruct/help them in loading & caching their maps correctly.
If you can't work on either of these 2 solutions, then I highly doubt there will be a way to do it. I don't see any other way to the best of my knowledge.
I've been asked to create a stand-alone site/app that's not connected to the web (all on a local server).
One part of it is to have a map of a natural reserve with a bunch of links that will show footpaths, different animals habitat areas, visitor centres and such.
So there's a map (static picture) and when you click on it some overlay goes on top of it.
At least that's the way I see it now.
I've looked here: http://www.carto.net/williams/yosemite/ but it just looks mucho ugly.
Getting Maps Premium is not an option as it's not that cheap. And the reason they don't want to use Maps/Earth free API is because internet connection is still very slow there (sattelite internet only and when optic cable will be hooked up nobody knows).
Looking for some recommendations as to how to proceed there. Drawing paths/areas on the picture of the maps seems extremely insufficient and time consuming.
I'd need some way to use coordinates to automatically draw areas and lines over the map (and then somehow export that as a graphis file (or SVG) that'll be layered on top of original map simply using ajax.
Will ARCGIS pro edition be the way to go or should I start learning SVG. Do you know some good SVG books/tutorials (as related to mapping)? Maybe there's some other way around altogether...
They do have detailed maps of the area in ARCGIS (whatever format they are in I don't know yet).
Just looking for some ideas, any help will be appreciated. Thanks in advance.
Do you know GeoServer? More or less all-in-one, compatible with different types of datasets, widely customisable.
Starting from "raw" SVG and write the whole thing yourself will probably be prohibitively time consuming.
If you have very little data (say less than 50 geometries) that is fixed, you could also use OpenLayers without any backend server.
For the data you could use a OpenLayers.Layer.Image if your (overlay-) map consists of a small raster image. For vector data, you can use OpenLayers.Layer.Text or a OpenLayers.Layer.Vecor together with protocols OpenLayers.Layer.KML or .JSON.
You can click through the current release examples.
I admit that this is not an easy task for a beginner, but it's fun hacking the maps together.
I want to create wayfinder/pathfinder mobile application. it will route visitors in our buildings. we have 20 buildings and each at least have 4 floor.
We want to develop our own wayfinder ex:http://www.wayfinderkiosk.com/
It should use Lat/Long coordinates to locate the people. and help to find its route.
So where should i start. Does any one have any idea for that. and it is going to be mobile.
I can develop app/site based on these platforms ( Mobile Web/Iphone/Adroid /Symbian/Windows )
But i need a start point. and i need your help.
Thanks
You want to use lat/long inside of a building? Assuming these visitors are going to be using their own unmodified devices, you may have trouble with GPS. Unless you somehow get reliable GPS signal despite being under a four-story building, that's probably not going to work.
An RFID-tagged badge and sensors placed throughout the building seems more likely to work. Put a unique QR-code on each badge that directs the phone's browser to a tracking page for that specific badge.
edit: and now that I re-read your question and see that multiple buildings are involved, the GPS bit could certainly work for routing them from one building to another.
planning to launch a comic site which serves comic strips (images).
I have little prior experience to serving/caching images.
so these are my 2 methods i'm considering:
1. Using LinkProperty
class Comic(db.Model)
image_link = db.LinkProperty()
timestamp = db.DateTimeProperty(auto_now=True)
Advantages:
The images are get-ed from the disk space itself ( and disk space is cheap i take it?)
I can easily set up app.yaml with an expiration date to cache the content in user's browser
I can set up memcache to retrieve the entities faster (for high traffic)
2. Using BlobProperty
I used this tutorial , it worked pretty neat. http://code.google.com/appengine/articles/images.html
Side question: Can I say that using BlobProperty sort of "protects" my images from outside linkage? That means people can't just link directly to the comic strips
I have a few worries for method 2.
I can obviously memcache these entities for faster reads.
But then:
Is memcaching images a good thing? My images are large (100-200kb per image). I think memcache allows only up to 4 GB of cached data? Or is it 1 Mb per memcached entity, with unlimited entities...
What if appengine's memcache fails? -> Solution: I'd have to go back to the datastore.
How do I cache these images in the user's browser? If I was doing method no. 1, I could just easily add to my app.yaml the expiration date for the content, and pictures get cached user side.
would like to hear your thoughts.
Should I use method 1 or 2? method 1 sounds dead simple and straightforward, should I be wary of it?
[EDITED]
How do solve this dilemma?
Dilemma: The last thing I want to do is to prevent people from getting the direct link to the image and putting it up on bit.ly because the user will automatically get directed to only the image on my server
( and not the advertising/content around it if the user had accessed it from the main page itself )
You're going to be using a lot of bandwidth to transfer all these images from the server to the clients (browsers). Remember appengine has a maximum number of files you can upload, I think it is 1000 but it may have increased recently. And if you want to control access to the files I do not think you can use option #1.
Option #2 is good, but your bandwidth and storage costs are going to be high if you have a lot of content. To solve this problem people usually turn to Content Delivery Networks (CDNs). Amazon S3 and edgecast.com are two such CDNs that support token based access urls. Meaning, you can generate a token in your appengine app that that is good for either the IP address, time, geography and some other criteria and then give your cdn url with this token to the requestor. The CDN serves your images and does the access checks based on the token. This will help you control access, but remember if there is a will, there is a way and you can't 100% secure anything - but you probably get reasonably close.
So instead of storing the content in appengine, you would store it on the cdn, and use appengine to create urls with tokens pointing to the content on the cdn.
Here are some links about the signed urls. I've used both of these :
http://jets3t.s3.amazonaws.com/toolkit/code-samples.html#signed-urls
http://www.edgecast.com/edgecast_difference.htm - look at 'Content Security'
In terms of solving your dilemma, I think that there are a couple of alternatives:
you could cause the images to be
rendered in a Flash object that would
download the images from your server
in some kind of encrypted format that
it would know how to decode. This would
involve quite a bit of up-front work.
you could have a valid-one-time link
for the image. Each time that you
generated the surrounding web page,
the link to the image would be
generated randomly, and the
image-serving code would invalidate
that link after allowing it one time. If you
have a high-traffic web-site, this would be a very
resource-intensive scheme.
Really, though, you want to consider just how much work it is worth to force people to see ads, especially when a goodly number of them will be coming to your site via Firefox, and there's almost nothing that you can do to circumvent AdBlock.
In terms of choosing between your two methods, there are a couple of things to think about. With option one, where are are storing the images as static files, you will only be able to add new images by doing an appcfg.py update. Since AppEngine application do not allow you to write to the filesystem, you will need to add new images to your development code and do a code deployment. This might be difficult from a site management perspective. Also, serving the images form memcache would likely not offer you an improvement performance over having them served as static files.
Your second option, putting the images in the datastore does protect your images from linking only to the extent that you have some power to control through logic if they are served or not. The problem that you will encounter is that making that decision is difficult. Remember that HTTP is stateless, so finding a way to distinguish a request from a link that is external to your application and one that is internal to your application is going to require trickery.
My personal feeling is that jumping through hoops to make sure that people can't see your comics with seeing ads is solving the prolbem the wrong way. If the content that you are publishing is worth protecting, people will flock to your website to enjoy it anyway. Through high volumes of traffic, you will more than make up for anyone who directly links to your image, thus circumventing a few ad serves. Don't try to outsmart your consumers. Deliver outstanding content, and you will make plenty of money.
Your method #1 isn't practical: You'd need to upload a new version of your app for each new comic strip.
Your method #2 should work fine. It doesn't automatically "protect" your images from being hotlinked - they're still served up on a URL like any other image - but you can write whatever code you want in the image serving handler to try and prevent abuse.
A third option, and a variant of #2, is to use the new Blob API. Instead of storing the image itself in the datastore, you can store the blob key, and your image handler just instructs the blobstore infrastructure what image to serve.