163 lines
4 KiB
Markdown
163 lines
4 KiB
Markdown
# nativeImage
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In Electron, for the APIs that take images, you can pass either file paths or
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`nativeImage` instances. An empty image will be used when `null` is passed.
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For example, when creating a tray or setting a window's icon, you can pass an
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image file path as a `String`:
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```javascript
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var appIcon = new Tray('/Users/somebody/images/icon.png');
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var window = new BrowserWindow({icon: '/Users/somebody/images/window.png'});
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```
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Or read the image from the clipboard which returns a `nativeImage`:
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```javascript
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var image = clipboard.readImage();
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var appIcon = new Tray(image);
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```
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## Supported Formats
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Currently `PNG` and `JPEG` image formats are supported. `PNG` is recommended
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because of its support for transparency and lossless compression.
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On Windows, you can also load an `ICO` icon from a file path.
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## High Resolution Image
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On platforms that have high-DPI support, you can append `@2x` after image's
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base filename to mark it as a high resolution image.
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For example if `icon.png` is a normal image that has standard resolution, then
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`icon@2x.png` will be treated as a high resolution image that has double DPI
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density.
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If you want to support displays with different DPI densities at the same time,
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you can put images with different sizes in the same folder and use the filename
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without DPI suffixes. For example:
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```text
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images/
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├── icon.png
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├── icon@2x.png
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└── icon@3x.png
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```
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```javascript
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var appIcon = new Tray('/Users/somebody/images/icon.png');
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```
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Following suffixes for DPI are also supported:
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* `@1x`
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* `@1.25x`
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* `@1.33x`
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* `@1.4x`
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* `@1.5x`
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* `@1.8x`
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* `@2x`
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* `@2.5x`
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* `@3x`
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* `@4x`
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* `@5x`
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## Template Image
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Template images consist of black and clear colors (and an alpha channel).
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Template images are not intended to be used as standalone images and are usually
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mixed with other content to create the desired final appearance.
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The most common case is to use template images for a menu bar icon so it can
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adapt to both light and dark menu bars.
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**Note:** Template image is only supported on OS X.
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To mark an image as a template image, its filename should end with the word
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`Template`. For example:
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* `xxxTemplate.png`
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* `xxxTemplate@2x.png`
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## Methods
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The `nativeImage` class has the following methods:
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### `nativeImage.createEmpty()`
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Creates an empty `nativeImage` instance.
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### `nativeImage.createFromPath(path)`
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* `path` String
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Creates a new `nativeImage` instance from a file located at `path`.
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### `nativeImage.createFromBuffer(buffer[, scaleFactor])`
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* `buffer` [Buffer][buffer]
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* `scaleFactor` Double (optional)
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Creates a new `nativeImage` instance from `buffer`. The default `scaleFactor` is
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1.0.
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### `nativeImage.createFromDataURL(dataURL)`
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* `dataURL` String
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Creates a new `nativeImage` instance from `dataURL`.
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## Instance Methods
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The following methods are available on instances of `nativeImage`:
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```javascript
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const nativeImage = require('electron').nativeImage;
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var image = nativeImage.createFromPath('/Users/somebody/images/icon.png');
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```
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### `image.toPng()`
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Returns a [Buffer][buffer] that contains the image's `PNG` encoded data.
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### `image.toJpeg(quality)`
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* `quality` Integer (**required**) - Between 0 - 100.
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Returns a [Buffer][buffer] that contains the image's `JPEG` encoded data.
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### `image.toDataURL()`
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Returns the data URL of the image.
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### `image.getNativeHandle()` _OS X_
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Returns a [Buffer][buffer] that stores C pointer to underlying native handle of
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the image. On OS X, a pointer to `NSImage` instance would be returned.
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Notice that the returned pointer is a weak pointer to the underlying native
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image instead of a copy, so you _must_ ensure that the associated
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`nativeImage` instance is kept around.
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### `image.isEmpty()`
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Returns a boolean whether the image is empty.
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### `image.getSize()`
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Returns the size of the image.
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[buffer]: https://nodejs.org/api/buffer.html#buffer_class_buffer
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### `image.setTemplateImage(option)`
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* `option` Boolean
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Marks the image as template image.
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### `image.isTemplateImage()`
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Returns a boolean whether the image is a template image.
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