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d3/docs/d3-array/blur.md
Mike Bostock 6d6c6792f1
vitepress docs (#3654)
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I know you removed the TODO but I was already trying to fill it in! I think just making the distinction of modules that touch the DOM and those that don't was super clarifying for me personally when I figured that out. And I always forget the most basic ref pattern (and still might've messed it up here). I don't think we should get into updating or interactivity or whatever, but I think just this much goes a long way toward demystifying (and showing just the most basic best practices).

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Co-authored-by: Mike Bostock <mbostock@gmail.com>

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Co-authored-by: Mike Bostock <mbostock@gmail.com>

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Co-authored-by: Toph Tucker <tophtucker@gmail.com>
2023-06-07 21:30:47 -04:00

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Markdown

# Blurring data
A [box blur](https://en.wikipedia.org/wiki/Box_blur) implementation for 1D, 2D, and RGBA images; supports fractional radius.
## blur(*data*, *radius*) {#blur}
```js
const numbers = d3.cumsum({length: 1000}, () => Math.random() - 0.5);
d3.blur(numbers, 5); // a smoothed random walk
```
[Examples](https://observablehq.com/@d3/d3-blur) · [Source](https://github.com/d3/d3-array/blob/main/src/blur.js) · Blurs an array of *data* in-place by applying three iterations of a moving average transform (box filter) for a fast approximation of a Gaussian kernel of the given *radius*, a non-negative number. Returns the given *data*.
## blur2({data, width, height}, *rx*, *ry*) {#blur2}
```js
const matrix = {
width: 4,
height: 3,
data: [
1, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 1
]
};
d3.blur2(matrix, 1);
```
[Examples](https://observablehq.com/@d3/d3-blur) · [Source](https://github.com/d3/d3-array/blob/main/src/blur.js) · Blurs a matrix of the given *width* and *height* in-place by applying a horizontal blur of radius *rx* and a vertical blur of radius *ry* (which defaults to *rx*). The matrix values *data* are stored in a flat (one-dimensional) array. If *height* is not specified, it is inferred from the given *width* and *data*.length. Returns the blurred matrix {data, width, height}.
## blurImage(*imageData*, *rx*, *ry*) {#blurImage}
```js
const imageData = context.getImageData(0, 0, width, height);
d3.blurImage(imageData, 5);
```
[Examples](https://observablehq.com/@d3/d3-blurimage) · [Source](https://github.com/d3/d3-array/blob/main/src/blur.js) · Blurs the given [ImageData](https://developer.mozilla.org/en-US/docs/Web/API/ImageData) in-place, blurring each of the RGBA layers independently by applying an horizontal blur of radius *rx* and a vertical blur of radius *ry* (which defaults to *rx*). Returns the blurred ImageData.