# Package javax.imageio.stream

package javax.imageio.stream
A package of the Java Image I/O API dealing with low-level I/O from files and streams.

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.

Since:
  1.4

- Related Packages
  Package
  Description
  javax.imageio
  The main package of the Java Image I/O API.
  javax.imageio.event
  A package of the Java Image I/O API dealing with synchronous notification of events during the reading and writing of images.
  javax.imageio.metadata
  A package of the Java Image I/O API dealing with reading and writing metadata.
  javax.imageio.spi
  A package of the Java Image I/O API containing the plug-in interfaces for readers, writers, transcoders, and streams, and a runtime registry.
- Class
  Description
  FileCacheImageInputStream
  An implementation of `ImageInputStream` that gets its input from a regular `InputStream`.
  FileCacheImageOutputStream
  An implementation of `ImageOutputStream` that writes its output to a regular `OutputStream`.
  FileImageInputStream
  An implementation of `ImageInputStream` that gets its input from a `File` or `RandomAccessFile`.
  FileImageOutputStream
  An implementation of `ImageOutputStream` that writes its output directly to a `File` or `RandomAccessFile`.
  IIOByteBuffer
  A class representing a mutable reference to an array of bytes and an offset and length within that array.
  ImageInputStream
  A seekable input stream interface for use by `ImageReader`s.
  ImageInputStreamImpl
  An abstract class implementing the `ImageInputStream` interface.
  ImageOutputStream
  A seekable output stream interface for use by `ImageWriter`s.
  ImageOutputStreamImpl
  An abstract class implementing the `ImageOutputStream` interface.
  MemoryCacheImageInputStream
  An implementation of `ImageInputStream` that gets its input from a regular `InputStream`.
  MemoryCacheImageOutputStream
  An implementation of `ImageOutputStream` that writes its output to a regular `OutputStream`.