Creating Adjusted Images Similar to UIButton’s AdjustsImageWhenHighlighted Effect

Overview

In this article, we will explore how to create adjusted images similar to UIButton’s adjustsImageWhenHighlighted effect. This effect is commonly seen on iOS buttons, where the image changes to a partially transparent gray when the button is highlighted or disabled.

Understanding AdjustsImageWhenHighlighted

The adjustsImageWhenHighlighted property of a UIButton is a boolean value that determines whether the button’s image should be adjusted for high lighting. When set to YES, the image will appear more vibrant and less faded, giving the impression of a highlighted state.

In contrast, when an image is not adjusted for highlights, it appears duller and less vibrant, mimicking the appearance of being “grayscaleed” or partially transparent.

Modifying Alpha Values

One way to achieve a similar effect is by modifying the alpha values of the images. By reducing the opacity of the image, we can create a partially transparent gray appearance that resembles the adjusted image effect.

To modify the alpha value, you can use the alpha property in your image views or buttons. This property sets the transparency level of the view, with 1.0 being fully opaque and 0.0 being fully transparent.

For example, if you have an UIImageView with a partially transparent gray background, you can set its alpha value to around 0.2, like this:

{
< highlight language="swift" >
    let imageView = UIImageView()
    imageView.backgroundColor = UIColor.grayWithAlpha(0.2)
}
{/ highlight }

In this example, grayWithAlpha is a utility function that returns a gray color with the specified alpha value.

Adding Partially Transparent Gray Image View

Another approach to creating an adjusted image effect is by adding a partially transparent gray image view over the button. This will effectively create a “grayscaleed” appearance, similar to the adjustsImageWhenHighlighted effect.

To achieve this, you can add a UIImageView with a partially transparent gray background over your button. The alpha value of the image view should be around 0.2 for a good balance between visibility and contrast.

Here’s an example:

{
< highlight language="swift" >
    let button = UIButton(type: .system)
    let imageView = UIImageView()
    
    // Set up the gray image view
    imageView.backgroundColor = UIColor.grayWithAlpha(0.2)
    imageView.frame = CGRect(x: 0, y: 0, width: button.frame.width, height: button.frame.height)
    
    // Add the image view to the button
    button.addSubview(imageView)
}
{/ highlight }

In this example, grayWithAlpha is a utility function that returns a gray color with the specified alpha value.

Using Core Image

For more advanced effects, you can use Core Image to create a partially transparent gray overlay on your images. This will give you more control over the appearance and behavior of the image adjustment effect.

To achieve this, you’ll need to use the CIImage class to create an image with the desired alpha value. Here’s an example:

{
< highlight language="swift" >
    import UIKit
    import CoreImage
    
    func applyGrayOverlay(image: UIImage) -> UIImage {
        // Create a new CIImage from the input image
        let ciImage = CIImage(image: image)!
        
        // Create a new CIVecto with the desired alpha value
        let vec = CIVector(cgPoint: CGPoint(x: 0.5, y: 0.5), size: CGSize(width: 1.0, height: 1.0))
        
        // Apply the overlay to the CIImage
        ciImage.setVector(vec)
        
        // Create a new UIImage from the modified CIImage
        let result = UIImage(ciImage: ciImage)!
        
        return result
    }
{/ highlight }

In this example, applyGrayOverlay is a utility function that takes an image as input and returns a new image with a partially transparent gray overlay.

Conclusion

Creating adjusted images similar to UIButton’s adjustsImageWhenHighlighted effect can be achieved through various methods, including modifying alpha values and using Core Image. By understanding the underlying principles of these techniques, you can create custom effects for your iOS applications that mimic the appearance of highlighted or disabled buttons.

In this article, we explored how to achieve a partially transparent gray appearance by adjusting the alpha value of images or using a gray image view as an overlay. We also discussed using Core Image to create more advanced effects, giving you control over the appearance and behavior of your images.

Whether you’re working with UIButton objects or creating custom views, these techniques can help you achieve the desired effect for your iOS applications.

Last modified on 2023-11-23