# init(device:thresholdValue:maximumValue:linearGrayColorTransform:) Initializes the kernel. ``` init(device: any MTLDevice, thresholdValue: Float, maximumValue: Float, linearGrayColorTransform transform: UnsafePointer?) ``` ## Parameters `device` The Metal device the filter will run on. `thresholdValue` The threshold value to use. `maximumValue` The maximum value to use. `transform` The color transform to use. This matrix is an array of 3 floats that defaults to the *BT.601/JPEG* standard: `{0.299f, 0.587f, 0.114f}` ## Return Value An initialized kernel object. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)