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  "title" : "differenceBlendMode()"
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# differenceBlendMode()

Subtracts color values to blend colors.

```
class func differenceBlendMode() -> any CIFilter & CICompositeOperation
```

## Return Value

The modified image.

## Discussion

This method applies the difference-blend mode filter to an image. The effect calculates the brightness value for both images and subtracts the smaller value, resulting in a slightly darker image. This effect doesn’t modify images that are black.

The difference-blend mode filter uses the following properties:

- `inputImage`: An image with the type [`CIImage`](/documentation/CoreImage/CIImage).
- `backgroundImage`: An image with the type [`CIImage`](/documentation/CoreImage/CIImage).

The following code creates a filter that blends colors in the background image and input image:

```swift
func differenceBlendMode(inputImage: CIImage, backgroundImage: CIImage) -> CIImage {
    let colorBlendFilter = CIFilter.differenceBlendMode()
    colorBlendFilter.inputImage = inputImage
    colorBlendFilter.backgroundImage = backgroundImage
    return colorBlendFilter.outputImage!
}
```

![The image on the top left shows a beach with multiple palm trees and a rainbow arching across the blue sky.  The image below is a gradient image displaying a gradual color shift from purple to a dark orange. The image on the right shows the output from applying a difference-blend mode filter. This displays colors from both images with the clarity and brightness from the beach rainbow image.](images/com.apple.coreimage/media-3546397@2x.png)

---

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