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DigitalMasterpieces/CoreImageExtensions
Useful extensions for Apple's Core Image framework
.package(url: "https://github.com/DigitalMasterpieces/CoreImageExtensions.git", from: "1.0.1")

CoreImageExtensions

Useful extensions for Apple's Core Image framework.

Image Lookup

We added a convenience initializer to CIImage that you can use to load an image by its name from an asset catalog or from a bundle directly:

let image = CIImage(named: "myImage")

This provides the same signature as the corresponding UIImage method:

// on iOS, Catalyst, tvOS
init?(named name: String, in bundle: Bundle? = nil, compatibleWith traitCollection: UITraitCollection? = nil)

// on macOS
init?(named name: String, in bundle: Bundle? = nil)

Images with Fixed Values

In Core Image, you can use the init(color: CIColor) initializer of CIImage to create an image with infinite extent that only contains pixels with the given color. This, however, only allows the creation of images filled with values in [0…1] since CIColor clamps values to this range.

We added two new factory methods on CIImage that allow the creation of images filled with arbitrary values:

/// Returns a `CIImage` with infinite extent only containing the given pixel value.
static func containing(values: CIVector) -> CIImage?

/// Returns a `CIImage` with infinite extent only containing the given value in RGB and alpha 1.
/// So `CIImage.containing(42.3)` would result in an image containing the value (42.3, 42.3, 42.3, 1.0) in each pixel.
static func containing(value: Double) -> CIImage?

This is useful, for instance, for passing scalar values into blend filters. For instance, this would create a color inversion effect in RGB:

var inverted = CIBlendKernel.multiply.apply(foreground: image, background: CIImage.containing(value: -1)!)!
inverted = CIBlendKernel.componentAdd.apply(foreground: inverted, background: CIImage.containing(value: 1)!)!

Image Value Access

It can be rather complicated to access the actual pixel values of a CIImage. The image needs to be rendered first and the resulting bitmap memory needs to be accessed properly.

We added some convenience methods to CIContext to do just that in a one-liner:

// get all pixel values of `image` as an array of `SIMD4<UInt8>` values:
let values = context.readUInt8PixelValues(from: image, in: image.extent)
let red: UInt8 = values[42].r // for instance

// get the value of a specific pixel as a `SIMD4<Float32>`:
let value = context.readFloat32PixelValue(from: image, at: CGPoint.zero)
let green: Float32 = value.g // for instance

These methods come in variants for accessing an area of pixels (in a given CGRect) or single pixels (at a given CGPoint). They are also available for three different data types: UInt8 (the normal 8-bit per channel format, with [0…255] range), Float32 (aka float containing arbitrary values, but colors are usually mapped to [0...1]), and Float16 (only on iOS).

OpenEXR Support

OpenEXR is an open standard for storing arbitrary bitmap data that exceed “normal” image color data, like 32-bit high-dynamic range data or negative floating point values (for instance for height fields).

Although Image I/O has native support for the EXR format, Core Image doesn’t provide convenience ways for rendering a CIImage into EXR. We added corresponding methods to CIContext for EXR export that align with the API provided for the other file formats:

// to create a `Data` object containing a 16-bit float EXR representation:
let exrData = try context.exrRepresentation(of: image, format: .RGBAh)

// to write a 32-bit float representation to an EXR file at `url`:
try context.writeEXRRepresentation(of: image, to: url, format: .RGBAf)

For reading EXR files into a CIImage, the usual initializers like CIImage(contentsOf: url) or CIImage(named: “myImage.exr” (see above) can be used.

OpenEXR Test Images

All EXR test images used in this project have been taken from here.

GitHub

link
Stars: 2
Last commit: 5 weeks ago

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iOS Software Engineer @ Perry Street Software
Perry Street Software is Jack’d and SCRUFF. We are two of the world’s largest gay, bi, trans and queer social dating apps on iOS and Android. Our brands reach more than 20 million members worldwide so members can connect, meet and express themselves on a platform that prioritizes privacy and security. We invest heavily into SwiftUI and using Swift Packages to modularize the codebase.

Release Notes

Build fixes
12 weeks ago

Small build fixes related to Xcode 14.5 and Catalyst.

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