MacOS screen annotation/presentation software

I was going to write a little application to let me annotate my MacOS screen during presentations, but the Ink2Go product looks like it does exactly what I was thinking. As I’m creating a video presentation, such as when showing how to write some Scala or Android code, I want to be able to draw on the screen, such as writing text, arrows, circles, and boxes to highlight parts of the screen. Ink2Go looks like what I want.

How to draw a circle in Android (onDraw method in View)

Android FAQ: How do I draw a circle in Android?

To draw a circle in Android you just need to create your own View class and then use that in your Activity. For example, the following CustomView shows how to extend a View and draw a circle in the onDraw method:

Why is this approach better? (FP and OOP)

For the last week or two I’ve been packing a few boxes every night as I prepare for a move a few miles to the north. Last night I started packing the old Beginning Scala book, when I noticed a bookmark I had in it. When I flipped to the bookmark, I found code like this:

trait Shape
case class Circle(radius: Double) extends Shape
case class Square(length: Double) extends Shape
case class Rectangle(h: Double, w: Double) extends Shape

which was later followed by code like this:

A Gimp circle tutorial: How to draw a circle in Gimp

Gimp circle FAQ: How do I draw a circle in Gimp?

I just used Gimp to create several circle images in my iPhone Safari browser privacy and security tutorial, and here's a short tutorial on how I created them. I normally use hollow circle images to highlight something in the original image, I'll demonstrate that here, but I'll also show how to create solid circles in Gimp, which are even easier to create.