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# contentAverageLightLevel

Returns the content average light level of the image.

```
var contentAverageLightLevel: Float { get }
```

## Discussion

If the image average light level is unknown, then the value 0.0 will be returned.

If the image headroom is known, then a value greater than or equal to 0.0 will be returned.

The image average light level may known when a CIImage is first initialized.
If the a CIImage is initialized with a:

- `CGImage` : then the headroom will be determined by `CGImageGetContentAverageLightLevel()`.
- `CVPixelBuffer` : then the headroom will be determined by `kCVImageBufferContentLightLevelInfoKey`.

If the image is the result of applying a [`CIFilter`](/documentation/CoreImage/CIFilter-swift.class) or [`CIKernel`](/documentation/CoreImage/CIKernel), this property will return `0.0`.

There are exceptions to this.  Applying a [`CIWarpKernel`](/documentation/CoreImage/CIWarpKernel) or certain [`CIFilter`](/documentation/CoreImage/CIFilter-swift.class)
(e.g. `CIGaussianBlur`, `CILanczosScaleTransform`, `CIAreaAverage` and some others)
to an image will result in a [`CIImage`](/documentation/CoreImage/CIImage) instance with the same `contentAverageLightLevel` property value.

---

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