Image Processing

Learn how to use existing image filters and create custom ones.

Overview

Nuke features a powerful and efficient image processing infrastructure with multiple built-in processors and an API for creating custom ones.

ImageRequest(url: url, processors: [
    .resize(size: imageView.bounds.size)
])

The built-in processors can all be found in the ImageProcessors namespace, but the preferred way to create them is by using static factory methods on ImageProcessing protocol.

Custom Processors

Custom processors need to implement ImageProcessing protocol. For the basic image processing needs, implement ImageProcessing/process(_:) method and create an identifier that uniquely identifies the processor. For processors with no input parameters, return a static string.

public protocol ImageProcessing {
    func process(image: UIImage) -> UIImage? // NSImage on macOS
    var identifier: String { get }
}

All processing tasks are executed on a dedicated queue (ImagePipeline/Configuration-swift.struct/imageProcessingQueue).

If your processor needs to manipulate image metadata (ImageContainer) or get access to more information via ImageProcessingContext, there is an additional method that you can implement in addition to ImageProcessing/process(_:context:)-26ffb.

public protocol ImageProcessing {
    func process(_ image container: ImageContainer, context: ImageProcessingContext) throws -> ImageContainer
}

In addition to ImageProcessing/identifier (a String), you can implement ImageProcessing/hashableIdentifier-2i3a7 to be used by the memory cache where string manipulations would be too slow. By default, this method returns the identifier string. If your processor conforms to Hashable protocol, it gets a default ImageProcessing/hashableIdentifier-2i3a7 implementation that returns self.

Topics

Image Processing

• ImageProcessing
• ImageProcessingOptions
• ImageProcessingContext
• ImageProcessingError

Built-In Processors

• ImageProcessing/resize(size:unit:contentMode:crop:upscale:)
• ImageProcessing/resize(width:unit:upscale:)
• ImageProcessing/resize(height:unit:upscale:)
• ImageProcessing/circle(border:)
• ImageProcessing/roundedCorners(radius:unit:border:)
• ImageProcessing/gaussianBlur(radius:)
• ImageProcessing/coreImageFilter(name:)
• ImageProcessing/coreImageFilter(name:parameters:identifier:)
• ImageProcessing/process(id:_:)
• ImageProcessors