CODEWITHSUNDEEP
c#objective-ciosuiimageviewxamarin.ios
Rodney S. Foley
Rodney S. Foley

Reputation: 10330

How to create an Image at construction of a UIImageView

I have a custom UIImageView and when it constructed I would like to create an in memory or cached to the iDevice Image that is a Filled Rectangle of a specific color and then set it to the UIImageView's Image property.

I know how to draw this on a UIImage by overriding the Draw method and it would just draw on the current CGContext. However since I want to do this at the time the UIImageView is constructed I don't actually have a context I can draw on or anything since it is not visible yet.

Simply put I am wondering if there is a way to do this programmatically at construction of the custom UIImageView when the app starts before anything is displayed to the screen.

I am okay with answers in C# or Objective-C.

Upvotes: 4

Views: 1461

Answers (1)

Matt Wilding
Matt Wilding

Reputation: 20153

Well, I can help you with the UIKit / Objective-C approach. As for .NET, I don't have the foggiest. UIKit has a few useful functions for programmatically generating UIImages. What you'll need to do is something like the following:

- (UIImage*)generateImage {

    UIGraphicsBeginImageContext(someCGSize);
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    // Draw whatever you want here with ctx, just like an overridden drawRect.

    UIImage* generatedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return generatedImage;
}

Just make sure you call such a method from the main thread. That's the only caveat I can think of.

[Edit] The C#/MonoTouch version is:

UIImage GenerateImage ()
{
    UIGraphics.BeginImageContext (new RectangleF (0, 0, 100, 100));
    var ctx = UIGraphics.GetCurrentContext ();

    // Draw into the ctx anything you want.
    var image = UIGraphics.GetImageFromCurrentImageContext ();
    UIGraphics.EndImageContext ();
    return image;
}

Upvotes: 6

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