iphone 怎样将UIImage对象保存到JPG或者PNG文件中？

我们都知道如果要从data中或者file中读取数据并包装成UIImage可以使用+ imageWithData: 和+ imageWithContentsOfFile: 但如果想把UIImage的图片数据写入到jpg或者png格式的文件中呢？答案是UIImageJPEGRepresentation，请看如下代码

[cpp] view
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/ Create paths to output images

NSString *pngPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Test.png"];

NSString *jpgPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Test.jpg"];

// Write a UIImage to JPEG with minimum compression (best quality)

// The value 'image' must be a UIImage object

// The value '1.0' represents image compression quality as value from 0.0 to 1.0

[UIImageJPEGRepresentation(image, 1.0) writeToFile:jpgPath atomically:YES];

// Write image to PNG

[UIImagePNGRepresentation(image) writeToFile:pngPath atomically:YES];

// Let's check to see if files were successfully written...

// Create file manager

NSError *error;

NSFileManager *fileMgr = [NSFileManager defaultManager];

// Point to Document directory

NSString *documentsDirectory = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];

// Write out the contents of home directory to console

NSLog(@"Documents directory: %@", [fileMgr contentsOfDirectoryAtPath:documentsDirectory error:&error]);