All posts by doug

UIWindow: When A UIViewController Just Won’t Cut It

When writing Huvi, I stumbled on a technique for when you need an Absolutely-Modal-And-I-Mean-It message to appear. There are a few cases where we need to make sure we know exactly what’s on the top of the view hierarchy, and that the user won’t go messing around with UI underneath.


One example is when the user doesn’t have an active internet connection. In that case, Huvi can’t do anything useful (it’s a streaming video app, after all), so we basically want to shut the user out of the app and say “go get some internet” when the connection is inactive. The trouble is, we can’t make any assumptions about what the user will be doing when the connection status changes. They could literally be anywhere in our app, and we need to be able to gracefully lock them out, then gracefully let them back in when the connection returns, placing them right where they left off.

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Huvi: Passcode Screen

The Huvi design called for a passcode screen for controlling access to parent mode and child profiles. Based on the designer’s mockups, this screen was to be translucent teal with white buttons, and a slight blur on the background. There were several opportunities to make this either a clean, reusable, maintainable module of code, or else a complete mess of copy-and-paste nonsense. I (hopefully) succeeded at making it the former.

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Huvi: Initial Logo Animation

Huvi’s splash screen displays the logo over a white background. Once the app launches, the user is taken to either the login/signup screen, or to the app’s “home” screen. In either case, I think the default “fade into a new screen” transition was a bit janky. The logo was right there, and then it just faded into a new location.

Good apps should feel “alive”, rather than like a collection of static views. Just because it’s easy to lay out an app’s flow in a storyboard, that’s no excuse for ignoring how those screens relate to one another, and creating pleasing transitions between them. The way a scene interfaces with other scenes is an important detail, and paying attention to those transitions can really help an app feel polished. There isn’t much that can’t benefit from a subtle bit of animation.

So, back to Huvi. Here’s what I accomplished for the transition from the splash logo to the initial screens:

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RadLab 2 Bitmap Painter Proof-Of-Concept

One of my goals for RadLab 2 is to have a local adjustments feature – a way for users to paint an effect onto (or off of) certain areas. This is a fundamentally important part of good photo editing, and the only reason RadLab 1 is useful without it is its Photoshop integration; but RadLab 2 is to be a standalone app, so that means I need to climb that mountain. And I did. Here’s the prototype app, and a brief explanation of what it does:

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PicTapGo Adjustments

One feature I always wanted from PicTapGo was some basic adjustment sliders for things like adding brightness or contrast to an image. The thumbnail-driven editing is intuitive, but can also be limiting when you are just looking for basic photo adjustments. And in version 3.0, that’s exactly what I did. It’s my favorite PicTapGo feature now, and I’m really proud of it.


The problem was always getting realtime performance from the image rendering. The Edit screen’s preview was originally displayed by a plain ol’ UIImageView – we render a UIImage, and set the view’s image to update it. Basic stuff. But you can’t do that 60 times a seconds. To get the “strength” slider producing realtime updates with the UIImageView-based display, we would render a full-strength image, and then just adjust the view’s alpha value, letting UIKit do the blending. This was a perfectly fine simulation of what Core Image would do in the final render, but it doesn’t work when you’re simultaneously adjusting 4 different parameters.

Enter GLKit, and GLKView.

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Don’t Block The Main Thread – Adventures in Concurrency

PicTapGo has always been pretty snappy. This was a result of some design decisions we made at the outset – we render images at the minimum size needed, do our best to limit the depth of the filter chain at any one point, and “cheat” with the strength slider by using an alpha blend in the UI, instead of re-rendering the image constantly. However, there was still some unnecessary lag in a few places, and in version 3.0, I made a point of cleaning them up.

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The PicTapGo Crop Tool

PicTapGo’s crop tool is a unique beast. The tool I envisioned was inspired by Lightroom’s crop/rotate tool, but needed to work within the limitations of a mobile / touch device interface. The requirements for the this feature were essentially:

  1. Allow the user to simultaneously manipulate rotation and crop;
  2. Behave the way the user expects (i.e. if you think it should work a certain way, then it will);
  3. Automatically adjust the image to ensure the crop rectangle is entirely contained within the the image canvas (no “fill pixels” at the edges or corners);
  4. Work non-destructively;
  5. Maximize the displayed size of the image; and
  6. Provide continuous controls, as well as discrete ones (i.e. sliders and buttons) to facilitate quick and fine adjustments, and to increase precision.

The resulting solution is, I think, still the best crop and rotate tool around, period. There are a lot of subtle bits that make it an intuitive, easy, powerful tool.

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