screencalc
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Calculate data about any display (width, height, ratio, area, density, etc.)
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[](https://www.npmjs.org/package/screencalc) [](https://www.npmjs.org/package/screencalc) [](https://travis-ci.org/theodorejb/ScreenCalc)
ScreenCalc is a powerful JavaScript module which makes it easy to answer almost any kind of question about the properties of a display. For example:
*What is the resolution of a 16:9 screen with 1,440,000 pixels?*
```javascript
var screen = new ScreenCalc({
ratio: 16/9,
pixelCount: 1440000
});
var w = screen.getPixelWidth(); // 1600
var h = screen.getPixelHeight(); // 900
```
*What are the physical dimensions and ppi of a 50-inch 1080p television screen?*
```javascript
var screen = new ScreenCalc({
pixelWidth: 1920,
pixelHeight: 1080,
diagonalSize: 50
});
var w = screen.getPhysicalWidth(); // 43.579
var h = screen.getPhysicalHeight(); // 24.513
var d = screen.getPixelDensity(); // 44.058
```
*What resolution is needed for a 27-inch 16:9 display with 300ppi?*
```javascript
var screen = new ScreenCalc({
diagonalSize: 27,
pixelDensity: 300,
ratio: 16/9
});
var w = screen.getPixelWidth(); // 7059.762
var h = screen.getPixelHeight(); // 3971.116
```
*What is the aspect ratio and diagonal size of a screen with an area of 8437.5 square centimeters and a width of 112.5 centimeters?*
```javascript
var screen = new ScreenCalc({
area: 8437.5,
physicalWidth: 112.5
});
var r = screen.getStringRatio(); // 3:2
var d = screen.getDiagonalSize(); // 135.2
```
Install using npm:
`npm install screencalc`
Require the module and instantiate with any combination of properties:
```javascript
var ScreenCalc = require('screencalc');
var screen = new ScreenCalc({
ratio: 16/10,
pixelDensity: 225,
physicalHeight: 4.5
});
```
1. ratio
2. pixelWidth
3. pixelHeight
4. pixelCount
5. pixelDensity
6. physicalWidth
7. physicalHeight
8. area
9. diagonalSize
Each of these properties has a corresponding *getPropertyName()* method (e.g. `getPixelHeight()`). Methods will throw an error if there is not enough data to perform the calculation:
```javascript
var noPixels = new ScreenCalc({
physicalWidth: 30,
physicalHeight: 18
});
noPixels.getPixelCount(); // Error: Insufficient data to calculate pixel count
```
**Note:** ScreenCalc intentionally avoids rounding any values calculated by these methods (including pixel width, pixel height, and pixel count). When working with imprecise data, be sure to round results as necessary.
### Simplified ratio calculation
In addition to the getter methods corresponding to each settable property, ScreenCalc comes with two additional methods for calculating simplified ratios: `getSimpleRatio()` and `getStringRatio()`.
`getSimpleRatio()` returns an object with `width` and `height` properties containing the simplified ratio. Additionally, a `difference` property stores the difference between the simplified ratio and the exact ratio of the screen. The difference will be zero if the simplified ratio is precise.
```javascript
var laptop = new ScreenCalc({
pixelWidth: 1366,
pixelHeight: 768
});
var ratio = laptop.getSimpleRatio(); // { width: 16, height: 9, difference: -0.0008680555555555802 }
```
`getStringRatio()` returns the same simplified ratio as `getSimpleRatio()`, but as a string in the format *width:height*. If the simplified ratio is not exact, a tilde will be prepended to the string:
```javascript
var strRatio = laptop.getStringRatio(); // "~16:9"
```
Both `getSimpleRatio()` and `getStringRatio()` accept an optional parameter to override the default precision. This parameter should be a number between 0 and 1, where values closer to zero increase the precision. If not specified, the precision will default to `5.0e-3`.
```javascript
var exactRatio = laptop.getSimpleRatio(1.0e-5); // { width: 683, height: 384, difference: 0 }
var exactStrRatio = laptop.getStringRatio(1.0e-5); // "683:384"
```
ScreenCalc is written in TypeScript. After editing files, run `npm install` to compile everything and create a browser test bundle. Run `npm test` to ensure all the tests pass, or use `test/browser/index.html` to run the tests in a browser. Bug reports and pull requests are welcome!
Theodore Brown
<http://theodorejb.me>
MIT