---
title: "generateMask(for:)"
framework: vision
role: symbol
role_heading: Instance Method
path: "vision/instancemaskobservation/generatemask(for:)"
---

# generateMask(for:)

Creates a low-resolution mask from the instances you specify.

## Declaration

```swift
func generateMask(for instances: IndexSet) throws -> CVPixelBuffer
```

## Parameters

- `instances`: An indexed set of selected instances, where 0 is the background.

## Return Value

Return Value The pixel buffer that contains the mask.

## See Also

### Generating a mask

- [generateMaskedImage(for:imageFrom:croppedToInstancesExtent:)](vision/instancemaskobservation/generatemaskedimage(for:imagefrom:croppedtoinstancesextent:).md)
- [generateScaledMask(for:scaledToImageFrom:)](vision/instancemaskobservation/generatescaledmask(for:scaledtoimagefrom:).md)