139 lines
3.2 KiB
Markdown
139 lines
3.2 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. When passing `null`, an empty image will be used.
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For example, when creating a tray or setting a window's icon, you can pass an image
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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:
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```javascript
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var clipboard = require('clipboard');
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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` are supported. It is recommended to use `PNG`
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because of its support for transparency and lossless compression.
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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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file name's base name 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, the
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`icon@2x.png` would 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 density at the same time, you
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can put images with different sizes in the same folder, and use the filename
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without DPI suffixes, like this:
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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 as DPI denses 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 image for menu bar icon so it can adapt
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to both light and dark menu bars.
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Template image is only supported on Mac.
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To mark an image as template image, its filename should end with the word
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`Template`, examples are:
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* `xxxTemplate.png`
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* `xxxTemplate@2x.png`
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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
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Creates a new `NativeImage` instance from `buffer`. The `scaleFactor` is 1.0 by
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default.
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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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## Class: NativeImage
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This class is used to represent an image.
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### NativeImage.toPng()
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Returns a [Buffer][buffer] that contains image's `PNG` encoded data.
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### NativeImage.toJpeg(quality)
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* `quality` Integer
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Returns a [Buffer][buffer] that contains image's `JPEG` encoded data.
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### NativeImage.toDataUrl()
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Returns the data URL of image.
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### NativeImage.isEmpty()
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Returns whether the image is empty.
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### NativeImage.getSize()
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Returns the size of the image.
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[buffer]: https://iojs.org/api/buffer.html#buffer_class_buffer
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### NativeImage.setTemplateImage(option)
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* `option` Boolean
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Marks the image as template image.
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