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electron/docs/api/native-image.md
Kevin Sawicki 089bfd2cd2 Document nativeImage.addRepresentation(options)
2017-03-09 09:56:42 -08:00

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nativeImage

Create tray, dock, and application icons using PNG or JPG files.

Process: Main, Renderer

In Electron, for the APIs that take images, you can pass either file paths or NativeImage instances. An empty image will be used when null is passed.

For example, when creating a tray or setting a window's icon, you can pass an image file path as a String:

const {BrowserWindow, Tray} = require('electron')

const appIcon = new Tray('/Users/somebody/images/icon.png')
let win = new BrowserWindow({icon: '/Users/somebody/images/window.png'})
console.log(appIcon, win)

Or read the image from the clipboard which returns a NativeImage:

const {clipboard, Tray} = require('electron')
const image = clipboard.readImage()
const appIcon = new Tray(image)
console.log(appIcon)

Supported Formats

Currently PNG and JPEG image formats are supported. PNG is recommended because of its support for transparency and lossless compression.

On Windows, you can also load ICO icons from file paths. For best visual quality it is recommended to include at least the following sizes in the:

  • Small icon
  • 16x16 (100% DPI scale)
  • 20x20 (125% DPI scale)
  • 24x24 (150% DPI scale)
  • 32x32 (200% DPI scale)
  • Large icon
  • 32x32 (100% DPI scale)
  • 40x40 (125% DPI scale)
  • 48x48 (150% DPI scale)
  • 64x64 (200% DPI scale)
  • 256x256

Check the Size requirements section in this article.

High Resolution Image

On platforms that have high-DPI support such as Apple Retina displays, you can append @2x after image's base filename to mark it as a high resolution image.

For example if icon.png is a normal image that has standard resolution, then icon@2x.png will be treated as a high resolution image that has double DPI density.

If you want to support displays with different DPI densities at the same time, you can put images with different sizes in the same folder and use the filename without DPI suffixes. For example:

images/
├── icon.png
├── icon@2x.png
└── icon@3x.png

const {Tray} = require('electron')
let appIcon = new Tray('/Users/somebody/images/icon.png')
console.log(appIcon)

Following suffixes for DPI are also supported:

  • @1x
  • @1.25x
  • @1.33x
  • @1.4x
  • @1.5x
  • @1.8x
  • @2x
  • @2.5x
  • @3x
  • @4x
  • @5x

Template Image

Template images consist of black and clear colors (and an alpha channel). Template images are not intended to be used as standalone images and are usually mixed with other content to create the desired final appearance.

The most common case is to use template images for a menu bar icon so it can adapt to both light and dark menu bars.

Note: Template image is only supported on macOS.

To mark an image as a template image, its filename should end with the word Template. For example:

  • xxxTemplate.png
  • xxxTemplate@2x.png

Methods

The nativeImage module has the following methods, all of which return an instance of the NativeImage class:

nativeImage.createEmpty()

Returns NativeImage

Creates an empty NativeImage instance.

nativeImage.createFromPath(path)

  • path String

Returns NativeImage

Creates a new NativeImage instance from a file located at path. This method returns an empty image if the path does not exist, cannot be read, or is not a valid image.

const nativeImage = require('electron').nativeImage

let image = nativeImage.createFromPath('/Users/somebody/images/icon.png')
console.log(image)

nativeImage.createFromBuffer(buffer[, options])

  • buffer Buffer
  • options Object (optional)
    • width Integer (optional) - Required for bitmap buffers.
    • height Integer (optional) - Required for bitmap buffers.
    • scaleFactor Double (optional) - Defaults to 1.0.

Returns NativeImage

Creates a new NativeImage instance from buffer.

nativeImage.createFromDataURL(dataURL)

  • dataURL String

Creates a new NativeImage instance from dataURL.

Class: NativeImage

Natively wrap images such as tray, dock, and application icons.

Process: Main, Renderer

Instance Methods

The following methods are available on instances of the NativeImage class:

image.toPNG([options])

  • options Object (optional)
    • scaleFactor Double (optional) - Defaults to 1.0.

Returns Buffer - A Buffer that contains the image's PNG encoded data.

image.toJPEG(quality)

  • quality Integer (required) - Between 0 - 100.

Returns Buffer - A Buffer that contains the image's JPEG encoded data.

image.toBitmap([options])

  • options Object (optional)
    • scaleFactor Double (optional) - Defaults to 1.0.

Returns Buffer - A Buffer that contains a copy of the image's raw bitmap pixel data.

image.toDataURL([options])

  • options Object (optional)
    • scaleFactor Double (optional) - Defaults to 1.0.

Returns String - The data URL of the image.

image.getBitmap([options])

  • options Object (optional)
    • scaleFactor Double (optional) - Defaults to 1.0.

Returns Buffer - A Buffer that contains the image's raw bitmap pixel data.

The difference between getBitmap() and toBitmap() is, getBitmap() does not copy the bitmap data, so you have to use the returned Buffer immediately in current event loop tick, otherwise the data might be changed or destroyed.

image.getNativeHandle() macOS

Returns Buffer - A Buffer that stores C pointer to underlying native handle of the image. On macOS, a pointer to NSImage instance would be returned.

Notice that the returned pointer is a weak pointer to the underlying native image instead of a copy, so you must ensure that the associated nativeImage instance is kept around.

image.isEmpty()

Returns Boolean - Whether the image is empty.

image.getSize()

Returns Object:

  • width Integer
  • height Integer

image.setTemplateImage(option)

  • option Boolean

Marks the image as a template image.

image.isTemplateImage()

Returns Boolean - Whether the image is a template image.

image.crop(rect)

  • rect Object - The area of the image to crop
    • x Integer
    • y Integer
    • width Integer
    • height Integer

Returns NativeImage - The cropped image.

image.resize(options)

  • options Object
    • width Integer (optional)
    • height Integer (optional)
    • quality String (optional) - The desired quality of the resize image. Possible values are good, better or best. The default is best. These values express a desired quality/speed tradeoff. They are translated into an algorithm-specific method that depends on the capabilities (CPU, GPU) of the underlying platform. It is possible for all three methods to be mapped to the same algorithm on a given platform.

Returns NativeImage - The resized image.

If only the height or the width are specified then the current aspect ratio will be preserved in the resized image.

image.getAspectRatio()

Returns Float - The image's aspect ratio.

image.addRepresentation(options)

  • options Object
    • scaleFactor Double - The scale factor to add the image representation for.
    • width Integer (optional)
    • height Integer (optional)
    • buffer Buffer (optional) - The buffer containing the raw image data.
    • dataURL String (optional) - The data URL containing either a base 64 encoded PNG or JPEG image.

Add an image representation for a specific scale factor. This can be used to explicitly add different scale factor representations to an image. This can be called on empty images.