---
title: "init(device:sigma:)"
framework: metalperformanceshaders
role: symbol
role_heading: Initializer
path: "metalperformanceshaders/mpsimagegaussianblur/init(device:sigma:)"
---

# init(device:sigma:)

Initializes a Gaussian blur filter.

## Declaration

```swift
init(device: any MTLDevice, sigma: Float)
```

## Parameters

- `device`: The Metal device the filter will run on.
- `sigma`: The standard deviation of the gaussian blur filter. Gaussian weight w, centered at 0, at integer grid i, is given as: w(i) = 1/sqrt(2*pi*sigma) * exp(-i^2/2*sigma^2) If we take cut off at 1% of w(0) (max weight) beyond which weights are considered 0, we have ceil(sqrt(-log(0.01)*2)*sigma) ~ ceil(3.7*sigma) as the rough estimate of the filter width.

## Return Value

Return Value An initialized Gaussian blur filter object.