iPhone UIImage保存到文件，PNG／JPEG自适应

+ (BOOL)writeImage:(UIImage*)image toFileAtPath:(NSString*)aPath

{

         if ((image == nil) || (aPath == nil) || ([aPath isEqualToString:@""]))

              return NO;

        

         @try

         {

              NSData *imageData = nil;

              NSString *ext = [aPath pathExtension];

              if ([ext isEqualToString:@"png"])

              {
                     imageData = UIImagePNGRepresentation(image);

              }
              else

              {

                     // the rest, we write to jpeg

                     // 0. best, 1. lost. about compress.

                     imageData = UIImageJPEGRepresentation(image, 0);    

              }

             

              if ((imageData == nil) || ([imageData length] <= 0))

                     return NO;

             

              [imageData writeToFile:aPath atomically:YES];      

              return YES;

         }

         @catch (NSException *e)

         {

              NSLog(@"create thumbnail exception.");

         }

        

         return NO;

}