How can I make an UIImage programmatically?

Question

This isn't what you probably thought it was to begin with. I know how to use UIImage's, but I now need to know how to create a "blank" UIImage using:

CGRect screenRect = [self.view bounds];

Well, those dimensions. Anyway, I want to know how I can create a UIImage with those dimensions colored all white. No actual images here.

Is this even possible? I am sure it is, but maybe I am wrong.

Edit

This needs to be a "white" image. Not a blank one. :)

Answer 1

You need to use CoreGraphics, as follows.

CGSize size = CGSizeMake(desiredWidth, desiredHeight); UIGraphicsBeginImageContextWithOptions(size, YES, 0); [[UIColor whiteColor] setFill]; UIRectFill(CGRectMake(0, 0, size.width, size.height)); UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); 

The code creates a new CoreGraphics image context with the options passed as parameters; size, opaqueness, and scale. By passing 0 for scale, iOS automatically chooses the appropriate value for the current device.

Then, the context fill colour is set to [UIColor whiteColor]. Immediately, the canvas is then actually filled with that color, by using UIRectFill() and passing a rectangle which fills the canvas.

A UIImage is then created of the current context, and the context is closed. Therefore, the image variable contains a UIImage of the desired size, filled white.

Answer 2

Swift version:

extension UIImage {      static func emptyImage(with size: CGSize) -> UIImage? {         UIGraphicsBeginImageContext(size)         let image = UIGraphicsGetImageFromCurrentImageContext()         UIGraphicsEndImageContext()         return image     }  }