Comment puis-je utiliser la fonctionnalité de dessin NSString pour créer un UIImage à partir du texte

Question

Je voudrais dessiner le contenu d'une variable dans un UIImage, mais je n'ai absolument aucune idée de comment faire cela. J'ai besoin d'écrire une méthode qui recevra un NSString comme paramètre et retournera un UIImage avec le texte dessiné dedans.

Answer 1

Vous pouvez essayer ceci: (mis à jour pour iOS 4)

-(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; 
} 

Pour appeler :

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

Answer 2

Begin un contexte d'image avec UIGraphicsBeginImageContext, attirer, obtenir une image avec UIGraphicsGetImageFromCurrentImageContext, fin avec UIGraphicsEndImageContext

Answer 3

Ajout d'une version Swift, vous donne également plus d'options:

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 
} 

Answer 4

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! 
} 

Le crédit va à Bao Lei pour la belle réponse.