Flutter package for displaying nine-patch images.
by Andrew Brampton (https://bramp.net/)
Pre-process and display nine-patch images at any display resolution.
A standard nine-patch format is a PNG with a special 1 pixel border around the outside that contains the metadata for the image.
These images can be made by numerous nine-patch editors, my favorite being this one. However, this border makes it more complex to load/render the image, as well as more difficult to manage/resize the image assets (as you have to avoid resizing this 1 pixel boundary). Thus, this library decides to seperate the Image and Metadata into two files, a plain PNG file and a JSON file. The PNG can be resized as normal to make 2.0x, 3.0x, etc, and the JSON file is scaled to the 1.0x.
[samples/TextBox_Side.9.json](https://github.com/bramp/nine_patch/blob/main/samples/TextBox_Side.9.json) |
[samples/2.0x/TextBox_Side.png](https://github.com/bramp/nine_patch/blob/main/samples/2.0x/TextBox_Side.png)
(without the 1 pixel border) |
```json { "stretch": { "x": 118, "y": 40, "width": 121, "height": 60 }, "contents": { "x": 19, "y": 18, "width": 248, "height": 101 }, "dimensions": { "x": 285, "y": 167 }, "name": "TextBox_Side.png", "scale": 2 } ``` | ![Example nine-patch PNG file named TextBox_Side.png](https://raw.githubusercontent.com/bramp/nine_patch/main/samples/2.0x/TextBox_Side.png) |
You can create the JSON metadata files easily with https://pub.dev/packages/nine_patcher, as part of your build pipeline.
To use the nine-patch image within a Flutter App, first include to dependency flutter pub add nine_patch
or manually add to your pubspec.yaml
:
dependencies:
nine_patch: ^1.0.0
Then create a NinePatchImage
widget where you need it, like so:
import 'package:nine_patch/nine_patch.dart';
...
// Create a new NinePatchImage widget
NinePatchImage.fromAssetMetadata(
name: "image.9.json",
)
You can also specify children (to be within the NinePatch):
NinePatchImage.fromAssetMetadata(
name: "image.9.json",
margin: EdgeInsets.all(10),
padding: EdgeInsets.all(10), // This is in addition to the fill area that may already be specificed in the nine-patch metadata.
child: Center(
child: child,
),
)
Finally, if your images/metadata are not in assets, you can provide any ImageProvider
and create the metadata from another source:
NinePatchImage(
image: NetworkImage("https://example.com/example.png"),
metadata: NinePatchMetadata(...),
)
The example image is from https://penzilla.itch.io/basic-gui-bundle.
This project is under BSD 3-clause:
BSD 3-Clause License
Copyright (c) 2023, Andrew Brampton (https://bramp.net)
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
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