Question

我尝试使用一个扩展程序获取彩色图像（star.jpg，只是一个星形图标）。结果，我得到整个UIImageView的颜色，包括我的形象。我怎么才能得到UIImage彩色？

以下是我使用的代码：的UIImage + Tinting.swift

import UIKit

extension UIImage {

func tintWithColor(color:UIColor)->UIImage {
    UIGraphicsBeginImageContext(self.size)
    let context = UIGraphicsGetCurrentContext()

    // Flip the image
    CGContextScaleCTM(context, 1.0, -1.0)
    CGContextTranslateCTM(context, 0.0, -self.size.height)

    // Multiply blend mode
    CGContextSetBlendMode(context, CGBlendMode.Multiply)

    let rect = CGRectMake(0, 0, self.size.width, self.size.height)
    CGContextClipToMask(context, rect, self.CGImage)
    color.setFill()
    CGContextFillRect(context, rect)

    // Create uiimage
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage
}

}

ViewController.swift

import UIKit

class ViewController: UIViewController {

let myImageview = UIImageView()
let myImage = UIImage(named: "star.jpg")

override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view, typically from a nib.
    myImageview.image = myImage
    let img = myImageview.image
    myImageview.image = img?.tintWithColor(UIColor.redColor())

    // Set position of the image view
    myImageview.translatesAutoresizingMaskIntoConstraints = false //Don't forget this line
    view.addSubview(myImageview)

    let horizontalConstraint = NSLayoutConstraint(item: myImageview, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: view, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0)
    view.addConstraint(horizontalConstraint)

    let verticalConstraint = NSLayoutConstraint(item: myImageview, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: view, attribute: NSLayoutAttribute.CenterY, multiplier: 1, constant: 0)
    view.addConstraint(verticalConstraint)

    let widthConstraint = NSLayoutConstraint(item: myImageview, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: view, attribute: NSLayoutAttribute.Width, multiplier: 0.5, constant: 0)
    view.addConstraint(widthConstraint)

    let heightConstraint = NSLayoutConstraint(item: myImageview, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: view, attribute: NSLayoutAttribute.Height, multiplier: 0.3, constant: 0)
    view.addConstraint(heightConstraint)
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}

Answer 1

使用以下代码使用tintColor更改UIImageView图像的外观。还提供了Alpha通道的样本图像。

// *** I assume you have define IBOutlet of your imageView or programatically created ***
@IBOutlet weak var ivStar: UIImageView!

// *** Set `UIImage` with rendering mode `AlwaysTemplate`
ivStar.image = UIImage(imageLiteral: "Star").imageWithRenderingMode(.AlwaysTemplate)

// *** Set TintColor on `UIImageView` as per your Appearance requirement ***
ivStar.tintColor = UIColor.blueColor();

带有Alpha PNG的样本星形图标

Star icon PNG

Answer 2

这样做：

<tr>
    <td>Select Country:
    </td>
    <td>
        <asp:DropDownList ID="ddlCountry"
                          runat="server"
                          AutoPostBack="True"
                          OnSelectedIndexChanged="ddlCountry_SelectedIndexChanged">
        </asp:DropDownList>
    </td>
</tr>

<tr>
    <td>Select City:
    </td>
    <td>
        <asp:DropDownList ID="ddlState" runat="server">

        </asp:DropDownList>
    </td>
</tr>

<强>更新

尝试复制你的确切设置，没有扩展中的上下文绘图，并进行基于扩展的色调（并非它非常聪明，在函数中已经作为swift的标准实现了，但只是为了它的乐趣）

    let image = UIImage(named: "yourimage");
    let tintedImage = image!.imageWithRenderingMode(.AlwaysTemplate)

    let imageView = UIImageView(frame: self.view.frame)
    imageView.image = tintedImage

    view.addSubview(imageView)

    imageView.tintColor = UIColor.redColor()

使用扩展程序获取彩色UIImage

2 个答案: