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# flashTransition()

Creates a flash of light to transition between two images.

```
class func flashTransition() -> any CIFilter & CIFlashTransition
```

## Return Value

The transition image.

## Discussion

This method applies the flash transition filter to an image. The effect transitions from the input image to the target image by creating a flash that fills the image and fades to the target image.

The flash transition filter uses the following properties:

- `inputImage`: The starting image with the type [`CIImage`](/documentation/CoreImage/CIImage).
- `targetImage`: The ending image with the type [`CIImage`](/documentation/CoreImage/CIImage).
- `center`: A set of coordinates marking the center of the image as a <doc://com.apple.documentation/documentation/CoreFoundation/CGPoint>.
- `extent`: A <doc://com.apple.documentation/documentation/CoreFoundation/CGRect> representing the size of the rounded rectangle.
- `color`: A [`CIColor`](/documentation/CoreImage/CIColor) representing the color of the flash effect.
- `time`: A `float` representing the parametric time of the transition from start (at time 0) to end (at time 1) as an <doc://com.apple.documentation/documentation/Foundation/NSNumber>.
- `maxStiriationRadius`: A `float` representing the radius of the light rays emanating from the flash as a <doc://com.apple.documentation/documentation/Foundation/NSNumber>.
- `striationStrength`: A `float` representing the strength of the light rays emanating from the flash as a <doc://com.apple.documentation/documentation/Foundation/NSNumber>.
- `striationContrast`: A `float` representing the contrast that’s added to each output pixel as a <doc://com.apple.documentation/documentation/Foundation/NSNumber>.
- `fadeThreshold`: A `float` representing the amount of fade between the flash and the target image as a <doc://com.apple.documentation/documentation/Foundation/NSNumber>.

The following code creates a filter that transitions from the input image with a large flash of light and fades to the target image.

```swift
func flash (inputImage: CIImage, targetImage: CIImage) -> CIImage {
    let flashTransition = CIFilter.flashTransition()
    flashTransition.inputImage = inputImage
    flashTransition.targetImage = targetImage
    flashTransition.center = CGPoint(x: 253, y: 372)
    flashTransition.extent = CGRect(x: 0, y: 0, width: 300, height: 300)
    flashTransition.color = .white
    flashTransition.time = 0.5
    flashTransition.maxStriationRadius = 2.58
    flashTransition.striationStrength = 0.5
    flashTransition.striationContrast = 1.375
    flashTransition.fadeThreshold = 0.06
    return flashTransition.outputImage!
}
```

![Three photographs. In the photo on the left, there are multiple small purple flowers photographed close up with good lighting, and the background has a slight blur. In the photograph on the right is a tall building with two trees directly in front of the building. In the center photograph, a flash transition filter is applied, resulting in a still photo of the moving transition. The left photograph is overlaid on the photo on the right while transitioning by creating a flash of light and slowly fading to the city image.](images/com.apple.coreimage/media-3616427@2x.png)

---

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