As I continue beavering away on my book, Core Image for Swift, I've been creating new custom filters. Some are simply composites of existing filters and some use CIKernel and GLSL. If you're patiently waiting on the book, you can get a sneaky preview of some of the stuff in the custom filters chapter over at Filterpedia where I'm adding these new filters.
Vignette Noir uses a vignette as a mask to transition between a high contrast black and white image at the edges and the original image towards the centre.
Mercurialize is an embossing filter that uses an embedded SceneKit scene to create its own shading image.
RGB Channel Tone Curve is based on Core Image's own tone curve filter but allows separate control the the red, green and blue channels. Filterpedia has a separate component for overlaying the three colour curves.
RGB Channel Gaussian Blur allows an image's three colour channels to be independently blurred.
Pseudo Colour is similar to Core Image's false colour but creates a luminance based gradient using five colours rather than two.
Kuwahara Filter is a smoothing filter that can give a painterly effect.
Filterpedia is available at my GitHub repository here.