如何使用NSString绘图function从文本创buildUIImage

我想在UIImage绘制一个NSStringvariables的内容，但我完全不知道如何做到这一点。 我需要编写一个方法，将接收一个NSString作为参数，并返回一个UIImage与绘制文本。

Answer 1

你可以试试这个：（更新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; } 

调用它：

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

Answer 2

添加一个Swift版本，也给你更多的select：

 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 3

用UIGraphicsBeginImageContext开始一个图像上下文，绘制它，用UIGraphicsGetImageFromCurrentImageContext获取图像，用UIGraphicsGetImageFromCurrentImageContext结束

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! } 

信贷去鲍磊美丽的答案。