---
title: "generateMask(forInstances:)"
framework: vision
role: symbol
role_heading: Instance Method
path: "vision/vninstancemaskobservation/generatemask(forinstances:)"
---

# generateMask(forInstances:)

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

## Declaration

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

## Parameters

- `instances`: The collection of instances.

## Return Value

Return Value The pixel buffer that contains the image.

## See Also

### Creating a Mask

- [generateMaskedImage(ofInstances:from:croppedToInstancesExtent:)](vision/vninstancemaskobservation/generatemaskedimage(ofinstances:from:croppedtoinstancesextent:).md)
- [generateScaledMaskForImage(forInstances:from:)](vision/vninstancemaskobservation/generatescaledmaskforimage(forinstances:from:).md)