iOS 在形状中心绘制文本

Question

我正在尝试在 iOS 的形状中心绘制文本，例如 Microsoft Office 的插入形状，请参阅：https://www.dropbox.com/s/cgqyyuvy6hcv5g8/Screenshot%202014-01-21%2013.48.17.png

我有一个用于形成形状的坐标数组，可以很好地创建实际形状。

我的第一个策略是遵循这个 stackoverflow 问题：Core Text With Asymmetric Shape on iOS 但是我只能让它在形状底部绘制文本。有什么方法可以让文本垂直和水平居中？

然后我查看了新的 TextKit，但我陷入了如何将 NSTextContainer 子类化以接受 CGPath 或坐标数组来创建要在其中绘制的文本容器的问题。

我的备用解决方案是使用 Core Text 在形状的中心坐标处绘制文本，但这会导致文本在某些形状（例如直角三角形）上绘制在形状之外。

或者，我可以使用任何其他方法在形状的中心获取一些文本吗？

Answer 1

这有点棘手。首先，您必须创建一个上下文。 （bounds.size是图片的大小）

UIGraphicsBeginImageContext(bounds.size); 
CGContextRef context = UIGraphicsGetCurrentContext();

然后获取文本的边界框：（font就是你要使用的字体）

CGSize textSize =
[yourText sizeWithAttributes:@{NSFontAttributeName:font}];

将文本绘制到上下文中（x 和 y 标记图像的中心）

[yourText drawAtPoint:CGPointMake(x, y) withAttributes:@{NSFontAttributeName:font}];

获取图片

UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); 

结束图像上下文

UIGraphicsEndImageContext();

我还没有测试过，但这是要走的路。

Answer 2

Swift 2.0 兼容。

我的目的是画一个圆形，里面有居中的文字。

struct UIUtility {

  static func imageWithColor(color: UIColor, circular : Bool) -> UIImage {
    let size : CGFloat = circular ? 100 : 1;
    let rect = CGRectMake(0.0, 0.0, size, size)
    UIGraphicsBeginImageContext(rect.size)
    let context = UIGraphicsGetCurrentContext()
    CGContextSetFillColorWithColor(context, color.CGColor)
    if(circular) {
        CGContextFillEllipseInRect(context, rect)
    }
    else {
        CGContextFillRect(context, rect)
    }
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return image
  }

  static func drawText(text: NSString, font: UIFont, image: UIImage, point: CGPoint, textColor: UIColor = UIColor.whiteColor()) -> UIImage {
    UIGraphicsBeginImageContext(image.size)
    image.drawInRect(CGRectMake(0, 0, image.size.width, image.size.height))
    let rect = CGRectMake(point.x, point.y, image.size.width, image.size.height)
    text.drawInRect(CGRectIntegral(rect), withAttributes: [ NSFontAttributeName: font, NSForegroundColorAttributeName : textColor ])
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return newImage
  }

  static func circleImageWithText(text text: String, font: UIFont, circleColor: UIColor, textColor: UIColor = UIColor.whiteColor()) -> UIImage {
    let image = UIUtility.imageWithColor(circleColor, circular: true)
    let textSize = NSString(string: text).sizeWithAttributes([ NSFontAttributeName: font])
    let centerX = (image.size.width / 2.0) - (textSize.width / 2.0)
    let centerY = (image.size.height / 2.0) - (textSize.height / 2.0)
    let middlePoint = CGPointMake(centerX, centerY)
    return UIUtility.drawText(text, font: font, image: image, point: middlePoint)
  }

}

使用此实用程序，我们可以通过以下方式轻松创建图像：

let font = UIFont()
let image = UIUtility.circleImageWithText(text: "Center text", font: font, circleColor: UIColor.blackColor())

Answer 3

我从这些答案和相关问题中挑选——没有一个是真正令人满意的——并想出了这个简单的解决方案：

    UIGraphicsBeginImageContext(CGSize.init(width: imageWidth, height: imageHeight))

    let string = "ABC" as NSString

    let attributes = [
            NSFontAttributeName : UIFont.systemFontOfSize(40),
            NSForegroundColorAttributeName : UIColor.redColor()
        ]

    // Get the width and height that the text will occupy.
    let stringSize = string.sizeWithAttributes(attributes)

    // Center a rect inside of the image
    // by going half the difference to the right and down.
    string.drawInRect(
        CGRectMake(
            (imageWidth - stringSize.width) / 2,
            (imageHeight - stringSize.height) / 2,
            stringSize.width,
            stringSize.height
        ),
        withAttributes: attributes
    )

    let newImage = UIGraphicsGetImageFromCurrentImageContext()

    UIGraphicsEndImageContext()

结果（不管颜色）：

Answer 4

Swift 3 Luca Davanzo 的回答版本

struct UIUtility {

static func imageWithColor(color: UIColor, circular: Bool) -> UIImage? {
    let size: CGFloat = circular ? 100 : 1;
    let rect = CGRect(x: 0.0, y: 0.0, width: size, height: size)
    UIGraphicsBeginImageContext(rect.size)
    if let context = UIGraphicsGetCurrentContext() {
        context.setFillColor(color.cgColor)
        if(circular) {
            context.fillEllipse(in: rect)
        }
        else {
            context.fill(rect)
        }
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }
    return nil
}

static func drawText(text: NSString, font: UIFont, image: UIImage, point: CGPoint, textColor: UIColor = UIColor.white) -> UIImage? {
    UIGraphicsBeginImageContext(image.size)
    image.draw(in: CGRect(x: 0, y: 0, width: image.size.width, height: image.size.height))
    let rect = CGRect(x: point.x, y: point.y, width: image.size.width, height: image.size.height)
    text.draw(in: rect.integral, withAttributes: [ NSFontAttributeName: font, NSForegroundColorAttributeName: textColor ])
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return newImage
}

static func circleImageWithText(text: String, font: UIFont, circleColor: UIColor, textColor: UIColor = UIColor.white) -> UIImage? {
    if let image = UIUtility.imageWithColor(color: circleColor, circular: true) {
        let textSize = NSString(string: text).size(attributes: [ NSFontAttributeName: font])
        let centerX = ((image.size.width) / 2.0) - (textSize.width / 2.0)
        let centerY = ((image.size.height) / 2.0) - (textSize.height / 2.0)
        let middlePoint = CGPoint(x: centerX, y: centerY)
        return UIUtility.drawText(text: text as NSString, font: font, image: image, point: middlePoint, textColor: textColor)
    }
    return nil
}
}