Package javax.imageio.stream

The ImageInputStream interface unifies streaming and file-based operations. An abstract base class, ImageInputStreamImpl is provided to simplify writing a new ImageInputStream class. Concrete implementation classes (FileImageInputStream, FileCacheImageInputStream, and MemoryCacheImageInputStream) are provided that allow input to come from a File or InputStream with or without the use of a temporary cache file.

The ImageOutputStream interface performs an analogous function for output. An abstract base class, ImageOutputStreamImpl is provided, along with concrete implementation classes (FileImageOutputStream, FileCacheImageOutputStream, and MemoryCacheImageOutputStream) are provided that allow output to go to a File or OutputStream with or without the use of a temporary cache file.

The IIOByteBuffer class provides an alternative way to perform reads of sequences of bytes that reduces the amount of internal data copying.

An ImageInputStream or ImageOutputStream may internally allocate system resources, such as a temporary cache file. Clients are encouraged to use a try-with-resources statement to ensure the ImageInputStream.close() or ImageInputStream.close() method is called which can promptly free those native resources. Otherwise there is the possibility they will leak and eventually cause the application to fail as well the possibility that not all data is flushed to the underlying output stream. A logical consequence of that is that this should be done before closing the destination OutputStream. A simple pattern would be

try (FileOutputStream fos = new FileOutputStream("out.jpg");
     ImageOutputStream ios = new FileCacheImageOutputStream(fos, null)) {
    ImageIO.write(img, "jpg", ios);
} catch (IOException e) {
} // implicit finally block closes the streams in the reverse order to opening

Sub-classers of these Image I/O API stream types can, to a limited extent, protect the application from the consequences of failures to close by adopting mechanisms such as Cleaner to free internal resources when it is no longer reachable. This is only necessary if there are any resources to release. However applications cannot rely on this, either for resource management, or for program correctness.