IIOReadProgressListener (Java Platform SE 8 )
Keywords: javax.imageio.event.IIOReadProgressListener interface
Date: 2026-08-19

javax.imageio.event

## Interface IIOReadProgressListener

- All Superinterfaces:
    EventListener

      public interface IIOReadProgressListener
      extends EventListener

  An interface used by `ImageReader` implementations to notify callers of their image and thumbnail reading methods of progress.

  This interface receives general indications of decoding progress (via the `imageProgress` and `thumbnailProgress` methods), and events indicating when an entire image has been updated (via the `imageStarted`, `imageComplete`, `thumbnailStarted` and `thumbnailComplete` methods). Applications that wish to be informed of pixel updates as they happen (for example, during progressive decoding), should provide an `IIOReadUpdateListener`.

  See Also:
    `IIOReadUpdateListener`, `ImageReader.addIIOReadProgressListener(javax.imageio.event.IIOReadProgressListener)`, `ImageReader.removeIIOReadProgressListener(javax.imageio.event.IIOReadProgressListener)`

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `imageComplete(ImageReader source)` Reports that the current image read operation has completed.
    `void` | `imageProgress(ImageReader source, float percentageDone)` Reports the approximate degree of completion of the current `read` call of the associated `ImageReader`.
    `void` | `imageStarted(ImageReader source, int imageIndex)` Reports that an image read operation is beginning.
    `void` | `readAborted(ImageReader source)` Reports that a read has been aborted via the reader's `abort` method.
    `void` | `sequenceComplete(ImageReader source)` Reports that a sequence of read operations has completed.
    `void` | `sequenceStarted(ImageReader source, int minIndex)` Reports that a sequence of read operations is beginning.
    `void` | `thumbnailComplete(ImageReader source)` Reports that a thumbnail read operation has completed.
    `void` | `thumbnailProgress(ImageReader source, float percentageDone)` Reports the approximate degree of completion of the current `getThumbnail` call within the associated `ImageReader`.
    `void` | `thumbnailStarted(ImageReader source, int imageIndex, int thumbnailIndex)` Reports that a thumbnail read operation is beginning.

- - ### Method Detail

    - #### sequenceStarted

          void sequenceStarted(ImageReader source,
                               int minIndex)

      Reports that a sequence of read operations is beginning. `ImageReader` implementations are required to call this method exactly once from their `readAll(Iterator)` method.
      Parameters:
        `source` - the `ImageReader` object calling this method.
        `minIndex` - the index of the first image to be read.

    - #### sequenceComplete

          void sequenceComplete(ImageReader source)

      Reports that a sequence of read operations has completed. `ImageReader` implementations are required to call this method exactly once from their `readAll(Iterator)` method.
      Parameters:
        `source` - the `ImageReader` object calling this method.

    - #### imageStarted

          void imageStarted(ImageReader source,
                            int imageIndex)

      Reports that an image read operation is beginning. All `ImageReader` implementations are required to call this method exactly once when beginning an image read operation.
      Parameters:
        `source` - the `ImageReader` object calling this method.
        `imageIndex` - the index of the image being read within its containing input file or stream.

    - #### imageProgress

          void imageProgress(ImageReader source,
                             float percentageDone)

      Reports the approximate degree of completion of the current `read` call of the associated `ImageReader`.

      The degree of completion is expressed as a percentage varying from `0.0F` to `100.0F`. The percentage should ideally be calculated in terms of the remaining time to completion, but it is usually more practical to use a more well-defined metric such as pixels decoded or portion of input stream consumed. In any case, a sequence of calls to this method during a given read operation should supply a monotonically increasing sequence of percentage values. It is not necessary to supply the exact values `0` and `100`, as these may be inferred by the callee from other methods.

      Each particular `ImageReader` implementation may call this method at whatever frequency it desires. A rule of thumb is to call it around each 5 percent mark.

      Parameters:
        `source` - the `ImageReader` object calling this method.
        `percentageDone` - the approximate percentage of decoding that has been completed.

    - #### imageComplete

          void imageComplete(ImageReader source)

      Reports that the current image read operation has completed. All `ImageReader` implementations are required to call this method exactly once upon completion of each image read operation.
      Parameters:
        `source` - the `ImageReader` object calling this method.

    - #### thumbnailStarted

          void thumbnailStarted(ImageReader source,
                                int imageIndex,
                                int thumbnailIndex)

      Reports that a thumbnail read operation is beginning. All `ImageReader` implementations are required to call this method exactly once when beginning a thumbnail read operation.
      Parameters:
        `source` - the `ImageReader` object calling this method.
        `imageIndex` - the index of the image being read within its containing input file or stream.
        `thumbnailIndex` - the index of the thumbnail being read.

    - #### thumbnailProgress

          void thumbnailProgress(ImageReader source,
                                 float percentageDone)

      Reports the approximate degree of completion of the current `getThumbnail` call within the associated `ImageReader`. The semantics are identical to those of `imageProgress`.
      Parameters:
        `source` - the `ImageReader` object calling this method.
        `percentageDone` - the approximate percentage of decoding that has been completed.

    - #### thumbnailComplete

          void thumbnailComplete(ImageReader source)

      Reports that a thumbnail read operation has completed. All `ImageReader` implementations are required to call this method exactly once upon completion of each thumbnail read operation.
      Parameters:
        `source` - the `ImageReader` object calling this method.

    - #### readAborted

          void readAborted(ImageReader source)

      Reports that a read has been aborted via the reader's `abort` method. No further notifications will be given.
      Parameters:
        `source` - the `ImageReader` object calling this method.

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