Update README.md

README.md

@@ -1,3 +1,43 @@
+![HistogramView](https://user-images.githubusercontent.com/156458/138126267-b1799ab2-87fe-4e7a-86bd-e36cdd9aa6bd.png)
+
 # HistogramView
 
-A description of this package.
+A SwiftUI view for displaying image histograms.
+
+## How do I use it?
+
+It's as simple as:
+``` swift
+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.
+
+``` swift
+/// 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 good 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](https://en.wikipedia.org/wiki/Hermite_interpolation) for generating a continous curve.
+The actual implementation for the interpolator is taken from [@FlexMonkey's implementation](https://github.com/FlexMonkey/Filterpedia/blob/7a0d4a7070894eb77b9d1831f689f9d8765c12ca/Filterpedia/components/HistogramDisplay.swift#L228) (part of the [Filterpedia](https://github.com/FlexMonkey/Filterpedia) project) and adapted to be used on `Path` instead of `UIBezierPath`.
+
+
+## Authors
+Vasilis Akoinoglou, [email protected]