转：使用CGContextShowTextAtPoint居中显示文本

转：使用CGContextShowTextAtPoint居中显示文本

创建：2012.08.29

转：选自CookBook IOS5

// Draw centered text into the context

void centerText(CGContextRef context, NSString *fontname, float textsize, NSString *text, CGPoint point, UIColor *color)

{

    CGContextSaveGState(context);

    CGContextSelectFont(context, [fontname UTF8String], textsize, kCGEncodingMacRoman);

    

    // Retrieve the text width without actually drawing anything

    CGContextSaveGState(context);

    CGContextSetTextDrawingMode( context, kCGTextInvisible);

    CGContextShowTextAtPoint( context, 0.0f, 0.0f, [text UTF8String], text.length);

    CGPoint endpoint = CGContextGetTextPosition( context);

    CGContextRestoreGState( context);

    

    // Query for size to recover height. Width is less reliable

    CGSize stringSize = [text sizeWithFont:[UIFont fontWithName:fontname size:textsize]];

    

    // Draw the text

    [color setFill];

    CGContextSetShouldAntialias( context, true);

    CGContextSetTextDrawingMode( context, kCGTextFill);

    CGContextSetTextMatrix (context, CGAffineTransformMake(1, 0, 0, -1, 0, 0));

    CGContextShowTextAtPoint( context, point.x - endpoint.x / 2.0f, point.y + stringSize.height / 4.0f, [text UTF8String], text.length); 

    CGContextRestoreGState( context);

}

＋＋＋＋＋