图片压缩

用法： 
UIImage *yourImage= [self imageWithImageSimple:image scaledToSize:CGSizeMake(210.0, 210.0)]; 
// 压缩图片 
- ( UIImage *)imageWithImageSimple:( UIImage *)image scaledToSize:( CGSize )newSize  
{  
// Create a graphics image context UIGraphicsBeginImageContext (newSize);  
// Tell the old image to draw in this newcontext, with the desired // new size [image  drawInRect : CGRectMake ( 0 , 0 ,newSize. width ,newSize. height )];  
// Get the new image from the context UIImage * newImage =  UIGraphicsGetImageFromCurrentImageContext ();  
// End the context UIGraphicsEndImageContext ();  
// Return the new image. return  newImage;  
}