Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
343 views
in Technique[技术] by (71.8m points)

iphone - UIImage color changing?

How can I change the UIImage's color through programming, any help please? If I send a UIImage, its color needs to change any help please? If I change the RGB color through bitmaphandling, it does not work.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Answer

0 votes
by (71.8m points)

If you only need it to look different, just use imageView.tintColor (iOS 7+). Catch is, setting tintColor doesn't do anything by default:

Why isn't my image blue?  I'm setting tintColor...

To make it work, use imageWithRenderingMode:

var image = UIImage(named: "stackoverflow")!
image = image.imageWithRenderingMode(.AlwaysTemplate)

let imageView = ...
imageView.tintColor = UIColor(red: 0.35, green: 0.85, blue: 0.91, alpha: 1)
imageView.image = image

And now it will work:

Now the image is orange!

Link to documentation.


Performance

Setting the image after configuring the UIImageView avoids repeating expensive operations:

// Good usage
let imageView = ...
imageView.tintColor = yourTintColor
var image = UIImage(named: "stackoverflow")!
image = image.imageWithRenderingMode(.AlwaysTemplate)
imageView.image = image        // Expensive

// Bad usage
var image = UIImage(named: "stackoverflow")!
image = image.imageWithRenderingMode(.AlwaysTemplate)
let imageView = ...
imageView.image = image        // Expensive
imageView.frame = ...          // Expensive
imageView.tintColor = yourTint // Expensive

Getting & setting the image asynchronously reduces scrolling and animation lag (especially when tinting an image inside of a UICollectionViewCell or UITableViewCell):

let imageView = cell.yourImageView
imageView.image = nil // Clear out old image
imageView.tintColor = UIColor(red: 0.35, green: 0.85, blue: 0.91, alpha: 1)

// Setting the image asynchronously reduces stuttering 
// while scrolling.  Remember, the image should be set as
// late as possible to avoid repeating expensive operations
// unnecessarily.
dispatch_async(dispatch_get_main_queue(), { () -> Void in
    var image = UIImage(named: "stackoverflow")!
    image = image.imageWithRenderingMode(.AlwaysTemplate)
    imageView.image = image
})

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...