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Added article for camera.

tags/v0.10.0
Nedyalko Nikolov 5 years ago
parent
commit
c40561ce7c
17 changed files with 94 additions and 15 deletions
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application-management.md View File

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nav-title: Application Management in NativeScript
title: "App: Management"
description: Learn how to manage the life cycle of NativeScript applications from application start to storing user-defined settings.
position: 6
position: 4
---

# Application Management


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bindings.md View File

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nav-title: "NativeScript Data Binding"
title: "App: Data Binding"
description: "NativeScript Documentation: Data Binding"
position: 8
position: 6
---

#Data Binding


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camera.md View File

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---
nav-title: "NativeScript Camera"
title: "App: Camera"
description: "NativeScript Documentation: Camera"
position: 10
---

#Camera

## Overview

Almost every mobile application need an option to capture an image and then share it. NativeScript camera module is dedicated for the first part of the job (taking picture).

### Using the camera module to take a picture

Using camera module is relative simple, however there are some points that need a little bit more explanation.

In order to use the camera module just require it like that:

``` JavaScript
var cameraModule = require("camera");
```
``` TypeScript
import cameraModule = require("camera");
```

Then we are ready to use it:

``` JavaScript
var imageModule = require("ui/image");
camera.takePicture().then(picture => {
console.log("Result is an image source instance");
var image = new imageModule.Image();
image.imageSource = picture;
});
```
``` TypeScript
import imageModule = require("ui/image");
camera.takePicture().then(picture => {
console.log("Result is an image source instance");
var image = new imageModule.Image();
image.imageSource = picture;
});
```

The above code will start the native platform camera application. After taking the picture and tapping the button `Save` (Android) or `use image` (iOS) the promise will resolve the `then` part and image source will be set as `imageSource` of the `ui/image` control.

> Note: Android specific - Android native camera application actually uses a file to store the image and then anybody (with granted access) could read the file and load the picture. By default NativeScript camera application uses a external files directory given by `Context.getExternalFilesDir(null)` to store a picture with name similar to `cameraPicture_ddmmyyyyHHMMSS.jpg`. The actual path to these files is `/sdcard/Android/data/applicationName/files/cameraPicture_ddmmyyyyHHMMSS.jpg`. Keep in mind that this file will not be deleted by camera module automatically, so developer must clear it out (if it is a critical manner). By default this directory will be deleted when the application is uninstalled.

### Taking a memory efficient picture

Previous example shows how to take a picture using the NativeScript camera module. However it takes a huge image (even mid-level devices has a 5MP camera which results in a image 2580x2048 which in bitmap means approximately 15 MB). In many cases we don't need such huge picture to show an image with 100x100 size, so taking a big picture is just a waste of memory. Camera module takePicture() method accepts an option parameter that could help in that case. With that option parameter we could set some properties like:

* width - The desired width of the picture (in device independent pixels).
* height - The desired height of the picture (in device independent pixels).
* keepAspectRatio - A boolean parameter that indicates if aspect ratio should be kept.

What `device independent pixels` means? NativeScript layout mechanism uses device independent pixels when measuring UI controls. This allows to declare one layout and this layout will look similar to all devices (no matter device display resolution). In order to get a proper image quality for high resolution devices (like iPhone retina and Android Full HD), camera module will return an image with bigger dimensions. For example if we request an image 100x100 on iPhone 6 actual image will be 200x200 (since its display density factor is 2 -> 100*2x100*2).
Setting `keepAspectRatio` property could result in a different than requested width or height. Camera module will return an image will correct aspect ratio but generally only one (from width and height) will be same as requested, the other value will be calculated in order to preserve the aspect of the original image.

Using the options parameter:

``` JavaScript
var imageModule = require("ui/image");
camera.takePicture({width: 300, height: 300, keepAspectRatio: true}).then(picture => {
console.log("Result is an image source instance");
var image = new imageModule.Image();
image.imageSource = picture;
});
```
``` TypeScript
import imageModule = require("ui/image");
camera.takePicture({width: 300, height: 300, keepAspectRatio: true}).then(picture => {
console.log("Result is an image source instance");
var image = new imageModule.Image();
image.imageSource = picture;
});
```

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events.md View File

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nav-title: Events in NativeScript
title: "App: Events"
description: How to handle events in NativeScript.
position: 9
position: 7
---

# Events


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faq.md View File

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nav-title: FAQ
title: "FAQ"
description: A list of frequently asked NativeScript questions and answers
position: 19
position: 18
---

# NativeScript FAQ


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gestures.md View File

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nav-title: Gestures in NativeScript
title: "UI: Gestures"
description: Learn what are the touch gestures that NativeScript supports and how to make use of them.
position: 16
position: 15

---



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index.md View File

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* [App: Handle Events](events.md)
* [App: Properties](properties.md)
* [App: Location](location.md)
* [App: Camera](camera.md)
* [UI: The Basics](ui-with-xml.md)
* [UI: Layouts](layouts.md)
* [UI: Widgets](modules.md)


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layouts.md View File

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nav-title: User Interface Layouts in NativeScript
title: "UI: Layouts"
description: Learn the basic principles of designing and positioning the UI elements inside your apps.
position: 13
position: 12
---

# User Interface Layouts


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location.md View File

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nav-title: Location in NativeScript
title: "App: Location"
description: How to work with geographical location data in NativeScript.
position: 11
position: 9
---

# Location


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modules.md View File

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nav-title: Modules in NativeScript
title: Modules
description: You can access the native device and platform capabilities of your target platform with the help of the NativeScript modules.
position: 5
position: 3
---

# Modules


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navigation.md View File

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nav-title: Architecture and Navigation in NativeScript
title: "App: Architecture and Navigation"
description: Learn the basic application structure of NativeScript apps and how to navigate inside your app.
position: 7
position: 5
---

# Architecture and Navigation


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properties.md View File

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nav-title: Properties in NativeScript
title: "App: Properties"
description: What is a property in NativeScript, what types of properties are available, and how to use them.
position: 10
position: 8
---

# Properties


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styling.md View File

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nav-title: Styling in NativeScript
title: "UI: Styling"
description: How to use Cascading Style Sheets (CSS) in NativeScript to change the appearance of GUI elements
position: 17
position: 16
---

# Styling


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troubleshooting.md View File

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nav-title: Troubleshooting
title: Troubleshooting
description: Known issues with NativeScript and their workarounds
position: 18
position: 17
---

# Known Issues and Limitations


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ui-dialogs.md View File

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nav-title: User Interface Dialogs in NativeScript
title: "UI: Dialogs"
description: Learn how to create alerts, confirmations, prompts, logins and other dialogs in your NativeScript apps.
position: 15
position: 14
---

# User Interface Dialogs


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nav-title: User Interface Widgets in NativeScript
title: "UI: Widgets"
description: Get familiar with the default user interface elements (widgets) in NativeScript.
position: 14
position: 13
---

# User Interface Widgets


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ui-with-xml.md View File

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nav-title: The User Interface in NativeScript
title: "UI: The Basics"
description: Learn the basic principles of designing a user interface with NativeScript. In NativeScript, you can design the UI using XML and CSS.
position: 12
position: 11
---

# The User Interface


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