往UIImage上写字的四种方法

第一种方法

//Add text to UIImage  
 
-(UIImage *)addText:(UIImage *)img text:(NSString *)text1{  
  
    int w = img.size.width;  
  
    int h = img.size.height;   
  
    //lon = h - lon;  
  
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();  
  
    CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);  
        
    CGContextDrawImage(context, CGRectMake(0, 0, w, h), img.CGImage);  
  
    CGContextSetRGBFillColor(context, 0.0, 0.0, 1.0, 1);  
     
    char* text  = (char *)[text1 cStringUsingEncoding:NSASCIIStringEncoding];// "05/05/09";  
  
    CGContextSelectFont(context, "Arial", 18, kCGEncodingMacRoman);  
  
    CGContextSetTextDrawingMode(context, kCGTextFill);  
  
    CGContextSetRGBFillColor(context, 255, 255, 255, 1);  
   
    //rotate text  
  
    CGContextSetTextMatrix(context, CGAffineTransformMakeRotation( -M_PI/4 ));  
  
    CGContextShowTextAtPoint(context, 4, 52, text, strlen(text));  
    
    CGImageRef imageMasked = CGBitmapContextCreateImage(context);  
  
    CGContextRelease(context);  
  
    CGColorSpaceRelease(colorSpace);  
      
   return [UIImage imageWithCGImage:imageMasked];  
 
} 

第二种方法： 

-(UIImage *)imageFromText:(NSString *)text

{    

　　UIFont *font = [UIFont systemFontOfSize:20.0];         

　　CGSize size  = [text sizeWithFont:font];     

　　UIGraphicsBeginImageContext(size);     

　　CGContextRef ctx = UIGraphicsGetCurrentContext();       
　　// optional: add a shadow      
　　// optional: also, to avoid clipping you should make the context size bigger     

　　CGContextSetShadowWithColor(ctx, CGSizeMake(2.0, -2.0), 5.0, [[UIColor grayColor] CGColor]);       
　　// draw in context       
　　[text drawAtPoint:CGPointMake(0.0, 0.0) withFont:font];      
　　// transfer image       
　　UIImage *image = UIGraphicsGetImageFromCurrentImageContext();          

　　UIGraphicsEndImageContext();          

　　return image;  
} 

第三种方法： 

UIImage *myImage = loadUnwatermarkedImage();   
NSString *myWatermarkText = @"Watermark";   
UIImage *watermarkedImage = nil;      
UIGraphicsBeginImageContext(myImage.size);   
[myImage drawAtPoint: CGPointZero];   
[myWatermarkText drawAtPoint: CGPointMake(10, 10) withFont: [UIFont systemFontOfSize: 12]];   
watermarkedImage = UIGraphicsGetImageFromCurrentImageContext();   
UIGraphicsEndImageContext(); 

 

第四种方法:

UIGraphicsBeginImageContext([parentView bounds].size);

[[parentView layer] renderInContext:UIGraphicsGetCurrentContext()];  

UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();