[iOS] About Drawing and Printing in iOS

• Drawing Paths
• use native drawing
• Core Graphics and UIKit
• using drawRect: method to draw shapges, text, images, or gradients
• redraw- call setNeedsDisplay or setNeedsDisplayInRect: method
• use OpenGL ES
• key concepts
• in drawRect: method, UIKit creates a graphics context to render
• coordination
• origin: top-left of the view
• logical coordination space
• distance: in points, not pixels