How do I draw on an image in Swift?

Question

I need to be able to programmatically draw on an image, and save that image for later use. Say, draw a line on specific x and y coordinates on the image, save the image, and

Answer 1

Updated Answer: Once you get the From and To coordinates, here is how to draw a line in a UIImage with those coordinates. From and To coordinates are in image pixels.

func drawLineOnImage(size: CGSize, image: UIImage, from: CGPoint, to: CGPoint) -> UIImage {

// begin a graphics context of sufficient size
UIGraphicsBeginImageContext(size)

// draw original image into the context
image.drawAtPoint(CGPointZero)

// get the context for CoreGraphics
let context = UIGraphicsGetCurrentContext()

// set stroking width and color of the context
CGContextSetLineWidth(context, 1.0)
CGContextSetStrokeColorWithColor(context, UIColor.blueColor().CGColor)

// set stroking from & to coordinates of the context
CGContextMoveToPoint(context, from.x, from.y)
CGContextAddLineToPoint(context, to.x, to.y)

// apply the stroke to the context
CGContextStrokePath(context)

// get the image from the graphics context 
let resultImage = UIGraphicsGetImageFromCurrentImageContext()

// end the graphics context 
UIGraphicsEndImageContext()

return resultImage }