A SwiftUI view for displaying image histograms.

How do I use it?

It’s as simple as:

HistogramView(image: myImage)

Note: Both UIImage & NSImage are supported (by the HistogramImage typealias, depending on the platform).

What options do I have for configuration?

The initializer supports channel opacity, blendMode and scale for the final graph.

/// The opacity of each channel layer. Default is `1`
public let channelOpacity: CGFloat

/// The blend mode for the channel layers. Default is `.screen`
public let blendMode: BlendMode

/// The scale of each layer. Default is `1`
public let scale: CGFloat

How fast is this thing?

Under the hood the histogram calculation is performed by Accelerate‘s vImageHistogramCalculation_ARGB8888 for RGB channels, so it’s pretty fast actually.
Fast enough to be perfomed synchronously (although didn’t test it on gigantic images).

How is the graph curve produced?

Each channel is a SwiftUI Path that uses Hermite interpolation for generating a continous curve.
The actual implementation for the interpolator is taken from @FlexMonkey’s implementation (part of the Filterpedia project) and adapted to be used on Path instead of UIBezierPath.


Vasilis Akoinoglou, [email protected]


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