开发笔记 那些年追过的图片(八):PNG，JPEG格式相互转换

先看下面的代码：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    NSString *mediaType = [info objectForKey:UIImagePickerControllerMediaType];
    if ([mediaType isEqualToString:@"public.image"]){
        image = [info objectForKey:@"UIImagePickerControllerOriginalImage"];
        NSData *data;
        if (UIImagePNGRepresentation(image) == nil)
{
            data = UIImageJPEGRepresentation(image, 1);
        } else {
            data = UIImagePNGRepresentation(image);
        }
        
        NSFileManager *fileManager = [NSFileManager defaultManager];
        NSString *filePath = [NSString stringWithString:[self getPath:@"image1"]];
        //将图片存储到本地documents

         [fileManager createDirectoryAtPath:filePath withIntermediateDirectories:YES attributes:nil error:nil];
         [fileManager createFileAtPath:[filePath stringByAppendingString:@"/image.png"] contents:dataattributes:nil];
        
        UIImage *editedImage = [[UIImage alloc] init];
        editedImage = image;
        CGRect rect = CGRectMake(0, 0, 64, 96);
        UIGraphicsBeginImageContext(rect.size);
        [editedImage drawInRect:rect];
        editedImage = UIGraphicsGetImageFromCurrentImageContext();
        
        UIButton *imageButton = [UIButton buttonWithType:UIButtonTypeCustom];
        imageButton.frame = CGRectMake(10, 10, 64, 96);
        [imageButton setImage:editedImage forState:UIControlStateNormal];
        [self.view addSubview:imageButton];
        [imageButton addTarget:self action:@selector(imageAction:)forControlEvents:UIControlEventTouchUpInside];

        [ipc dismissModalViewControllerAnimated:YES];
    } else {
        NSLog(@"MEdia");
    }
    
上面的代码是当从相册里面选取图片之后保存到本地程序沙盒，在上面我们得到的图片中不能够得到图片名字，以及不清楚图片格式，所以这个时候我们需要将其转换成NSdata二进制存储，
 image = [info objectForKey:@"UIImagePickerControllerOriginalImage"];

NSData *data;
        if (UIImagePNGRepresentation(image) == nil)
{
            data = UIImageJPEGRepresentation(image, 1);
        } else {
            data = UIImagePNGRepresentation(image);
        }
UIImagePNGRepresentation转换PNG格式的图片为二进制，如果图片的格式为JPEG则返回nil；
 [fileManager createFileAtPath:[filePath stringByAppendingString:@"/image.png"] contents:data attributes:nil];
   将图片保存为PNG格式

 [fileManager createFileAtPath:[filePath stringByAppendingString:@"/image.jpg"] contents:data attributes:nil];
  将图片保存为JPEG格式

我们也可以写成下面的格式存储图片
NSString *pngImage = [filePath stringByAppendingPathComponent:@"Documents/image.png"];
NSString *jpgImage = [filePath stringByAppendingPathComponent:@"Documents/image.jpg"];

[data writeToFile:pngImage atomically:YES];
[data writeToFile:jpgImage atomically:YES];