# ImageFilter.blur default tile mode automatic selection.

> If a tile mode wasn't specified in the constructor, ImageFilter.blur will select one based on the rendering context.




:::important
These breaking change docs are accurate, as of the release
under which they are published. Over time, the
workarounds described here might become inaccurate.
We don't, in general, keep these breaking change docs up
to date as of each release.

这些破坏性改动文档的准确性仅限于其发布时对应的版本。
随着时间的推移，文档中描述的方案可能会逐渐失效。
通常情况下，我们不会在每次发布新版本时都对这些文档进行同步更新。

The [breaking change index file](/release/breaking-changes)
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[破坏性改动列表](/release/breaking-changes) 
列出了每个版本的文档。

:::


## Summary

The `ui.ImageFilter.blur`'s default tile mode is
now automatically selected by the backend.
Previously `TileMode.clamp` was used unless a different tile mode was specified.
Now, the default is `null` and specifies automatic selection unless
a specific tile mode is specified.

## Background

`ImageFilter.blur`'s _tile mode_ specifies what happens to
edge pixels for the applied filter.
There are four options:

- `TileMode.clamp` (the previous default)
- `Tilemode.repeated`
- `TileMode.mirror`
- `TileMode.decal`

Previously, if the behavior wasn't specified,
`ImageFilter` defaulted to `clamp` mode.
This sometimes surprised developers as it didn't always match expectations.

As of this change, the filter automatically selects the
following tile modes based on context:

* `decal` with save layers and when applied to individual shape draws
          (such as with `drawRect` and `drawPath`).
* `mirror` with backdrop filters.
* `clamp` for `drawImage`.

## Migration guide

Only blur image filters that don't specify an explicit tile mode are
impacted by this change.

We believe that the new defaults are generally
better and would recommend removing any specified blur tile modes.

Code before migration:

```dart
final filter = ui.ImageFilter.blur(sigmaX: 4, sigmaY: 4, tileMode: TileMode.decal);
```

Code after migration:

```dart
final filter = ui.ImageFilter.blur(sigmaX: 4, sigmaY: 4);
```

## Timeline

Landed in version: 3.28.0-0.1.pre<br>
In stable release: 3.29

## References

API documentation:

* [`ImageFilter`][]
* [`TileMode`][]

Relevant issues:

* [Issue #154935][]
* [Issue #110318][]
* [Issue #157693][]

Relevant PRs:

* [Change default TileMode for blur ImageFilter objects to null][]

[`ImageFilter`]: https://api.flutter-io.cn/flutter/dart-ui/ImageFilter-class.html
[`ImageFilter.blur`]: https://api.flutter-io.cn/flutter/dart-ui/ImageFilter/ImageFilter.blur.html
[`TileMode`]: https://api.flutter-io.cn/flutter/dart-ui/TileMode.html
[Issue #154935]: https://github.com/flutter/flutter/issues/154935
[Issue #110318]: https://github.com/flutter/flutter/issues/110318
[Issue #157693]: https://github.com/flutter/flutter/issues/157693
[Change default TileMode for blur ImageFilter objects to null]: https://github.com/flutter/engine/pull/55552