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NSStringの描画機能を使用してテキストからUIImageを作成する方法

NSString変数の内容をUIImageに描画したいのですが、これを行う方法がまったくわかりません。パラメータとしてNSStringを受け取り、テキストが描画されたUIImageを返すメソッドを作成する必要があります。

iphonensstringuiimage
36
Jab

あなたはこれを試すことができます：（iOS 4用に更新されました）

-(UIImage *)imageFromText:(NSString *)text
{
    // set the font type and size
    UIFont *font = [UIFont systemFontOfSize:20.0];  
    CGSize size  = [text sizeWithFont:font];

    // check if UIGraphicsBeginImageContextWithOptions is available (iOS is 4.0+)
    if (UIGraphicsBeginImageContextWithOptions != NULL)
        UIGraphicsBeginImageContextWithOptions(size,NO,0.0);
    else
        // iOS is < 4.0 
        UIGraphicsBeginImageContext(size);

    // optional: add a shadow, to avoid clipping the shadow you should make the context size bigger 
    //
    // CGContextRef ctx = UIGraphicsGetCurrentContext();
    // CGContextSetShadowWithColor(ctx, CGSizeMake(1.0, 1.0), 5.0, [[UIColor grayColor] CGColor]);

    // draw in context, you can use also drawInRect:withFont:
    [text drawAtPoint:CGPointMake(0.0, 0.0) withFont:font];

    // transfer image
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();    

    return image;
}

それを呼び出すには：

UIImage *image = [self imageFromText:@"This is a text"];
89
rpmx

Swiftバージョンを追加すると、さらに多くのオプションが表示されます。

class func sizeOfAttributeString(str: NSAttributedString, maxWidth: CGFloat) -> CGSize {
    let size = str.boundingRectWithSize(CGSizeMake(maxWidth, 1000), options:(NSStringDrawingOptions.UsesLineFragmentOrigin), context:nil).size
    return size
}

class func imageFromText(text:NSString, font:UIFont, maxWidth:CGFloat, color:UIColor) -> UIImage {
    let paragraph = NSMutableParagraphStyle()
    paragraph.lineBreakMode = NSLineBreakMode.ByWordWrapping
    paragraph.alignment = .Center // potentially this can be an input param too, but i guess in most use cases we want center align

    let attributedString = NSAttributedString(string: text, attributes: [NSFontAttributeName: font, NSForegroundColorAttributeName: color, NSParagraphStyleAttributeName:paragraph])

    let size = sizeOfAttributeString(attributedString, maxWidth: maxWidth)
    UIGraphicsBeginImageContextWithOptions(size, false , 0.0)
    attributedString.drawInRect(CGRectMake(0, 0, size.width, size.height))
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return image
}
14
Bao Lei

UIGraphicsBeginImageContextで画像コンテキストを開始し、それに描画し、UIGraphicsGetImageFromCurrentImageContextで画像を取得し、UIGraphicsEndImageContextで終了します

2
user23743

Swift 3.1

func sizeOfAttributeString(str: NSAttributedString, maxWidth: CGFloat) -> CGSize {
    let size = str.boundingRect(with: CGSize(width: maxWidth, height: 1000), options:(NSStringDrawingOptions.usesLineFragmentOrigin), context:nil).size
    return size
}

func imageFromText(text:NSString, font:UIFont, maxWidth:CGFloat, color:UIColor) -> UIImage {
    let paragraph = NSMutableParagraphStyle()
    paragraph.lineBreakMode = NSLineBreakMode.byWordWrapping
    paragraph.alignment = .center 

    let attributedString = NSAttributedString(string: text as String, attributes: [NSFontAttributeName: font, NSForegroundColorAttributeName: color, NSParagraphStyleAttributeName:paragraph])

    let size = sizeOfAttributeString(str: attributedString, maxWidth: maxWidth)
    UIGraphicsBeginImageContextWithOptions(size, false , 0.0)
    attributedString.draw(in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    return image!
}

クレジットはバオレイの美しい答えに使われます。

2
Masih