IOS开发之保存图片到Documents目录及PNG，JPEG格式相互转换

查看原文http://blog.csdn.net/sanpintian/article/details/7418755

示例代码:

- (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];