illumimarty / imahen2

Simple image filtering app using CoreImage and Metal shaders

Imahen - iOS Image Filter App

Overview

Imahen -- Tagalog for "image" or "visual representation" of something

I created this app to explore the uses of common image effects used in CoreImage. I also leverage Metal kernels to perform popular image processing techniques on the device's GPU. Along the way, I also intend to make the user experience intuitive, similar to Instagram's photo editing interface.

Product Spec

User Stories (Required and Optional)

Required Must-have Stories

• User can use photos taken from camera or photo library for filtering
• User can apply a filter or image processing technique to a given image
• User can compare original and filtered images when pressing on the preview
• User can apply multiple filters one after the other
• User can adjust filter intensity when applying to image
• User can save to gallery or share to third-party apps

Optional Nice-to-have Stories

• User can see a history of which filters they've applied (sort of like a copy/paste clipboard or previously visited browser pages in a tab)

Supported and Planned Filters

Filters

• Grayscale Noir
• Sepia

Enhance

• Brightness
• Contrast (using histogram equalization)
• Smoothing (using Gaussian blurring)
• Sharpening

Advanced (using Metal shaders)

• Gradient w.r.t. x-axis
• Gradient w.r.t. y-axis
• Sobel edge detection filter
• Canny edge detection filter
• Otsu binarization

GIF Demo Walkthrough

Data Model

Imahen Filter

Property	Data Type	Desc
name	String?	name of filter / img proc. scheme
filter	CIFilter?
key	String?	Specifies which property to change in CIFilter
threshold	CGFloat?	0.0 to 1.0, typically used for filter intensity
filterType	FilterType	.coreImage or .metal

Some things I learned along the way

I anticipated for this app to be super simple in complexity, however I found it very useful to tap into my OOP knowledge. Even though by nature UIKit is object-oriented based and relies on keeping track of parent/children classes like Views and ViewControllers, it was interesting to practice it on the very classes I made for my specific use case. Not only was it super helpful to utilize structs/classes to create data models, but also keeping in mind inheritance/subclassing and method overriding when creating the user experience for applying filters.