降低UIImage的DPI分辨率

[mailComposer addAttachmentData:UIImageJPEGRepresentation(self.editedImageView.image, 1.0f)
                           mimeType:@\"image/jpeg\" 
                           fileName:@\"yourPhotoWithBestGlasses.jpg\"];

NSData = UIImageJPEGRepresentation(rightPhoto, 0.5);

NSData *imageData = UIImageJPEGRepresentation(originalImage, 0.5);

UIImage *tImage = [[UIImage alloc] initWithData:imageData];

originalImage = [tImage copy];

[tImage release];