how to draw and scale text in rectangle - iphone

Question

My question is simple. I have a rectangle,e.g. (0.0, 0.0, 300, 45), and need to draw a string, e.g. "Text" in the center of this rectangle. The height of "Text" must be fitted the height of rectangle.
And the hard part is: the rectangle can be scaled. The size of "Text" must be scaled as the size of rectangle.
I can draw string in center of rectangle as the coding below, but the difficult point is I cannot manage the "Text" font size changed as the rectangle size.
[#"Text" drawInRect:textRect withFont:font];
I want to draw text in a rectangle, not label, and the user can scale the rectangle size with his finger, finally, I will draw text on an image in scale, I think the label is not for those functions.
Anyone have good solution?
Thanks!
Update:
Actually, I need to draw text on large image in scale, not just show it on iphone screen, please look at the following code:
UIImageVIew *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0.0, 0.0, 320, 320)];
imageView.image = [UIImage imageNamed:#"LargeSizeImage"]; // Image size = 2048 *2048
[self.view addSubview:imageView];
UILabel *textLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 10, 300, 45)];
textLabel.text = #"Text";
[self.view addSubviews:textLabel];
// Draw text on image
UIGraphicsBeginImageCurrentContext(imageView.image.size);(2048 * 2048)
[imageView.image drawInRect:CGRectMake(0, 0, 2048, 2048)];
CGRect scaleRect = CGRectMake(10 * scaleFactor, 10 *scaleFactor, textLabel.bounds.size.width * scaleFactor, text.Label.bounds.size.height *scaleFactor);
UIFont *font = [UIFont systemOfSize:**?**];
[textLabel.text drawInRect:scaleRect withFont:font];
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My question is how do I determine the font size?

Answer 1

UILabel *text = [[UILabel alloc] initWithFrame:CGRectMake(0.0, 0.0, 300, 45)];
text.backgroundColor = [UIColor clearColor];
text.font = [UIFont systemFontOfSize:45];
text.textAlignment = UITextAlignmentCenter;
text.text = #"TEXT";
[self.view addSubview:text];
Would probably get the effect you are interested in.
EDIT
Actually you could dynamically size the text if you resize the square. In the method you do the resizes just add these lines of code for the UILabel to trigger a resizing.
text.frame = CGRectMake(0.0, 0.0, rect.frame.size.width, rect.frame.size.height);
text.font = [UIFont systemFontOfSize:rect.frame.size.height];
rect is what I am using to describe the rectangle you are resizing.