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# bumpDistortion()

Distorts an image with a concave or convex bump.

```
class func bumpDistortion() -> any CIFilter & CIBumpDistortion
```

## Return Value

The distorted image.

## Discussion

This method applies the bump distortion filter to an image. This effect creates a concave or convex bump defined by the `scale`. A value of 0.0 has no effect, while a positive value creates an outward curvature and a negative value creates an inward curvature.

The bump distortion filter uses the following properties:

- `inputImage`: An image with the type [`CIImage`](/documentation/CoreImage/CIImage).
- `radius`: A `float` representing the amount of pixels the filter uses to create the distortion as an <doc://com.apple.documentation/documentation/Foundation/NSNumber>.
- `center`: A <doc://com.apple.documentation/documentation/CoreFoundation/CGPoint> representing the center of the effect.
- `scale`: A `float` representing the curvature of the bump effect as an <doc://com.apple.documentation/documentation/Foundation/NSNumber>.

The following code creates a filter that results in a concave bump distorting the image:

```swift
func bump(inputImage: CIImage) -> CIImage {
    let filter = CIFilter.bumpDistortion()
    filter.inputImage = inputImage
    filter.center = CGPoint(x: 500, y: 500)
    filter.radius = 1200
    filter.scale = 2
    return filter.outputImage!
}
```

![Three images arranged horizontally. On the left, an image with a checkerboard pattern. In the middle, the checkerboard image with a positive scale bump distortion applied, the image appears to bulge out. On the right, the checkerboard image with a negative scale bump distortion applied, the image appears pushed in.](images/com.apple.coreimage/media-4407303@2x.png)

---

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