# Class IIOParam

java.lang.Object
javax.imageio.IIOParam

Direct Known Subclasses:
  `ImageReadParam, ImageWriteParam`

public abstract class IIOParam extends Object
A superclass of all classes describing how streams should be decoded or encoded. This class contains all the variables and methods that are shared by `ImageReadParam` and `ImageWriteParam`.

This class provides mechanisms to specify a source region and a destination region. When reading, the source is the stream and the in-memory image is the destination. When writing, these are reversed. In the case of writing, destination regions may be used only with a writer that supports pixel replacement.

Decimation subsampling may be specified for both readers and writers, using a movable subsampling grid.

Subsets of the source and destination bands may be selected.

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `protected IIOParamController`
  `controller`
  The `IIOParamController` that will be used to provide settings for this `IIOParam` object when the `activateController` method is called.
  `protected IIOParamController`
  `defaultController`
  The default `IIOParamController` that will be used to provide settings for this `IIOParam` object when the `activateController` method is called.
  `protected Point`
  `destinationOffset`
  The offset in the destination where the upper-left decoded pixel should be placed.
  `protected ImageTypeSpecifier`
  `destinationType`
  An `ImageTypeSpecifier` to be used to generate a destination image when reading, or to set the output color type when writing.
  `protected int[]`
  `sourceBands`
  An array of `int`s indicating which source bands will be used, or `null`.
  `protected Rectangle`
  `sourceRegion`
  The source region, on `null` if none is set.
  `protected int`
  `sourceXSubsampling`
  The decimation subsampling to be applied in the horizontal direction.
  `protected int`
  `sourceYSubsampling`
  The decimation subsampling to be applied in the vertical direction.
  `protected int`
  `subsamplingXOffset`
  A horizontal offset to be applied to the subsampling grid before subsampling.
  `protected int`
  `subsamplingYOffset`
  A vertical offset to be applied to the subsampling grid before subsampling.

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `IIOParam()`
  Protected constructor may be called only by subclasses.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `boolean`
  `activateController()`
  Activates the installed `IIOParamController` for this `IIOParam` object and returns the resulting value.
  `IIOParamController`
  `getController()`
  Returns whatever `IIOParamController` is currently installed.
  `IIOParamController`
  `getDefaultController()`
  Returns the default `IIOParamController`, if there is one, regardless of the currently installed controller.
  `Point`
  `getDestinationOffset()`
  Returns the offset in the destination image at which pixels are to be placed.
  `ImageTypeSpecifier`
  `getDestinationType()`
  Returns the type of image to be returned by the read, if one was set by a call to `setDestination(ImageTypeSpecifier)`, as an `ImageTypeSpecifier`.
  `int[]`
  `getSourceBands()`
  Returns the set of source bands to be used.
  `Rectangle`
  `getSourceRegion()`
  Returns the source region to be used.
  `int`
  `getSourceXSubsampling()`
  Returns the number of source columns to advance for each pixel.
  `int`
  `getSourceYSubsampling()`
  Returns the number of rows to advance for each pixel.
  `int`
  `getSubsamplingXOffset()`
  Returns the horizontal offset of the subsampling grid.
  `int`
  `getSubsamplingYOffset()`
  Returns the vertical offset of the subsampling grid.
  `boolean`
  `hasController()`
  Returns `true` if there is a controller installed for this `IIOParam` object.
  `void`
  `setController(IIOParamController controller)`
  Sets the `IIOParamController` to be used to provide settings for this `IIOParam` object when the `activateController` method is called, overriding any default controller.
  `void`
  `setDestinationOffset(Point destinationOffset)`
  Specifies the offset in the destination image at which future decoded pixels are to be placed, when reading, or where a region will be written, when writing.
  `void`
  `setDestinationType(ImageTypeSpecifier destinationType)`
  Sets the desired image type for the destination image, using an `ImageTypeSpecifier`.
  `void`
  `setSourceBands(int[] sourceBands)`
  Sets the indices of the source bands to be used.
  `void`
  `setSourceRegion(Rectangle sourceRegion)`
  Sets the source region of interest.
  `void`
  `setSourceSubsampling(int sourceXSubsampling, int sourceYSubsampling, int subsamplingXOffset, int subsamplingYOffset)`
  Specifies a decimation subsampling to apply on I/O.

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### sourceRegion

    protected Rectangle sourceRegion
    The source region, on `null` if none is set.

  - ### sourceXSubsampling

    protected int sourceXSubsampling
    The decimation subsampling to be applied in the horizontal direction. By default, the value is `1`. The value must not be negative or 0.

  - ### sourceYSubsampling

    protected int sourceYSubsampling
    The decimation subsampling to be applied in the vertical direction. By default, the value is `1`. The value must not be negative or 0.

  - ### subsamplingXOffset

    protected int subsamplingXOffset
    A horizontal offset to be applied to the subsampling grid before subsampling. The first pixel to be used will be offset this amount from the origin of the region, or of the image if no region is specified.

  - ### subsamplingYOffset

    protected int subsamplingYOffset
    A vertical offset to be applied to the subsampling grid before subsampling. The first pixel to be used will be offset this amount from the origin of the region, or of the image if no region is specified.

  - ### sourceBands

    protected int[] sourceBands
    An array of `int`s indicating which source bands will be used, or `null`. If `null`, the set of source bands to be used is as described in the comment for the `setSourceBands` method. No value should be allowed to be negative.

  - ### destinationType

    protected ImageTypeSpecifier destinationType
    An `ImageTypeSpecifier` to be used to generate a destination image when reading, or to set the output color type when writing. If non has been set the value will be `null`. By default, the value is `null`.

  - ### destinationOffset

    protected Point destinationOffset
    The offset in the destination where the upper-left decoded pixel should be placed. By default, the value is (0, 0).

  - ### defaultController

    protected IIOParamController defaultController
    The default `IIOParamController` that will be used to provide settings for this `IIOParam` object when the `activateController` method is called. This default should be set by subclasses that choose to provide their own default controller, usually a GUI, for setting parameters.
    See Also:
      - `IIOParamController`
      - `getDefaultController()`
      - `activateController()`

  - ### controller

    protected IIOParamController controller
    The `IIOParamController` that will be used to provide settings for this `IIOParam` object when the `activateController` method is called. This value overrides any default controller, even when null.
    See Also:
      - `IIOParamController`
      - `setController(IIOParamController)`
      - `hasController()`
      - `activateController()`

- ## Constructor Details

  - ### IIOParam

    protected IIOParam()
    Protected constructor may be called only by subclasses.

- ## Method Details

  - ### setSourceRegion

    public void setSourceRegion(Rectangle sourceRegion)
    Sets the source region of interest. The region of interest is described as a rectangle, with the upper-left corner of the source image as pixel (0, 0) and increasing values down and to the right. The actual number of pixels used will depend on the subsampling factors set by `setSourceSubsampling`. If subsampling has been set such that this number is zero, an `IllegalStateException` will be thrown.

    The source region of interest specified by this method will be clipped as needed to fit within the source bounds, as well as the destination offsets, width, and height at the time of actual I/O.

    A value of `null` for `sourceRegion` will remove any region specification, causing the entire image to be used.

    Parameters:
      `sourceRegion` - a `Rectangle` specifying the source region of interest, or `null`.
    Throws:
      `IllegalArgumentException` - if `sourceRegion` is non-`null` and either `sourceRegion.x` or `sourceRegion.y` is negative.
      `IllegalArgumentException` - if `sourceRegion` is non-`null` and either `sourceRegion.width` or `sourceRegion.height` is negative or 0.
      `IllegalStateException` - if subsampling is such that this region will have a subsampled width or height of zero.
    See Also:
      - `getSourceRegion()`
      - `setSourceSubsampling(int, int, int, int)`
      - `setDestinationOffset(Point)`
      - `getDestinationOffset()`

  - ### getSourceRegion

    public Rectangle getSourceRegion()
    Returns the source region to be used. The returned value is that set by the most recent call to `setSourceRegion`, and will be `null` if there is no region set.
    Returns:
      the source region of interest as a `Rectangle`, or `null`.
    See Also:
      - `setSourceRegion(Rectangle)`

  - ### setSourceSubsampling

    public void setSourceSubsampling(int sourceXSubsampling, int sourceYSubsampling, int subsamplingXOffset, int subsamplingYOffset)
    Specifies a decimation subsampling to apply on I/O. The `sourceXSubsampling` and `sourceYSubsampling` parameters specify the subsampling period (i.e., the number of rows and columns to advance after every source pixel). Specifically, a period of 1 will use every row or column; a period of 2 will use every other row or column. The `subsamplingXOffset` and `subsamplingYOffset` parameters specify an offset from the region (or image) origin for the first subsampled pixel. Adjusting the origin of the subsample grid is useful for avoiding seams when subsampling a very large source image into destination regions that will be assembled into a complete subsampled image. Most users will want to simply leave these parameters at 0.

    The number of pixels and scanlines to be used are calculated as follows.

    The number of subsampled pixels in a scanline is given by

    `truncate[(width - subsamplingXOffset + sourceXSubsampling - 1) / sourceXSubsampling]`.

    If the region is such that this width is zero, an `IllegalStateException` is thrown.

    The number of scanlines to be used can be computed similarly.

    The ability to set the subsampling grid to start somewhere other than the source region origin is useful if the region is being used to create subsampled tiles of a large image, where the tile width and height are not multiples of the subsampling periods. If the subsampling grid does not remain consistent from tile to tile, there will be artifacts at the tile boundaries. By adjusting the subsampling grid offset for each tile to compensate, these artifacts can be avoided. The tradeoff is that in order to avoid these artifacts, the tiles are not all the same size. The grid offset to use in this case is given by:
    grid offset = [period - (region offset modulo period)] modulo period)

    If either `sourceXSubsampling` or `sourceYSubsampling` is 0 or negative, an `IllegalArgumentException` will be thrown.

    If either `subsamplingXOffset` or `subsamplingYOffset` is negative or greater than or equal to the corresponding period, an `IllegalArgumentException` will be thrown.

    There is no `unsetSourceSubsampling` method; simply call `setSourceSubsampling(1, 1, 0, 0)` to restore default values.

    Parameters:
      `sourceXSubsampling` - the number of columns to advance between pixels.
      `sourceYSubsampling` - the number of rows to advance between pixels.
      `subsamplingXOffset` - the horizontal offset of the first subsample within the region, or within the image if no region is set.
      `subsamplingYOffset` - the horizontal offset of the first subsample within the region, or within the image if no region is set.
    Throws:
      `IllegalArgumentException` - if either period is negative or 0, or if either grid offset is negative or greater than the corresponding period.
      `IllegalStateException` - if the source region is such that the subsampled output would contain no pixels.

  - ### getSourceXSubsampling

    public int getSourceXSubsampling()
    Returns the number of source columns to advance for each pixel.

    If `setSourceSubsampling` has not been called, 1 is returned (which is the correct value).

    Returns:
      the source subsampling X period.
    See Also:
      - `setSourceSubsampling(int, int, int, int)`
      - `getSourceYSubsampling()`

  - ### getSourceYSubsampling

    public int getSourceYSubsampling()
    Returns the number of rows to advance for each pixel.

    If `setSourceSubsampling` has not been called, 1 is returned (which is the correct value).

    Returns:
      the source subsampling Y period.
    See Also:
      - `setSourceSubsampling(int, int, int, int)`
      - `getSourceXSubsampling()`

  - ### getSubsamplingXOffset

    public int getSubsamplingXOffset()
    Returns the horizontal offset of the subsampling grid.

    If `setSourceSubsampling` has not been called, 0 is returned (which is the correct value).

    Returns:
      the source subsampling grid X offset.
    See Also:
      - `setSourceSubsampling(int, int, int, int)`
      - `getSubsamplingYOffset()`

  - ### getSubsamplingYOffset

    public int getSubsamplingYOffset()
    Returns the vertical offset of the subsampling grid.

    If `setSourceSubsampling` has not been called, 0 is returned (which is the correct value).

    Returns:
      the source subsampling grid Y offset.
    See Also:
      - `setSourceSubsampling(int, int, int, int)`
      - `getSubsamplingXOffset()`

  - ### setSourceBands

    public void setSourceBands(int[] sourceBands)
    Sets the indices of the source bands to be used. Duplicate indices are not allowed.

    A `null` value indicates that all source bands will be used.

    At the time of reading, an `IllegalArgumentException` will be thrown by the reader or writer if a value larger than the largest available source band index has been specified or if the number of source bands and destination bands to be used differ. The `ImageReader.checkReadParamBandSettings` method may be used to automate this test.

    Semantically, a copy is made of the array; changes to the array contents subsequent to this call have no effect on this `IIOParam`.

    Parameters:
      `sourceBands` - an array of integer band indices to be used.
    Throws:
      `IllegalArgumentException` - if `sourceBands` contains a negative or duplicate value.
    See Also:
      - `getSourceBands()`
      - `ImageReadParam.setDestinationBands(int[])`
      - `ImageReader.checkReadParamBandSettings(ImageReadParam, int, int)`

  - ### getSourceBands

    public int[] getSourceBands()
    Returns the set of source bands to be used. The returned value is that set by the most recent call to `setSourceBands`, or `null` if there have been no calls to `setSourceBands`.

    Semantically, the array returned is a copy; changes to array contents subsequent to this call have no effect on this `IIOParam`.

    Returns:
      the set of source bands to be used, or `null`.
    See Also:
      - `setSourceBands(int[])`

  - ### setDestinationType

    public void setDestinationType(ImageTypeSpecifier destinationType)
    Sets the desired image type for the destination image, using an `ImageTypeSpecifier`.

    When reading, if the layout of the destination has been set using this method, each call to an `ImageReader` `read` method will return a new `BufferedImage` using the format specified by the supplied type specifier. As a side effect, any destination `BufferedImage` set by `ImageReadParam.setDestination(BufferedImage)` will no longer be set as the destination. In other words, this method may be thought of as calling `setDestination((BufferedImage)null)`.

    When writing, the destination type maybe used to determine the color type of the image. The `SampleModel` information will be ignored, and may be `null`. For example, a 4-banded image could represent either CMYK or RGBA data. If a destination type is set, its `ColorModel` will override any `ColorModel` on the image itself. This is crucial when `setSourceBands` is used since the image's `ColorModel` will refer to the entire image rather than to the subset of bands being written.

    Parameters:
      `destinationType` - the `ImageTypeSpecifier` to be used to determine the destination layout and color type.
    See Also:
      - `getDestinationType()`

  - ### getDestinationType

    public ImageTypeSpecifier getDestinationType()
    Returns the type of image to be returned by the read, if one was set by a call to `setDestination(ImageTypeSpecifier)`, as an `ImageTypeSpecifier`. If none was set, `null` is returned.
    Returns:
      an `ImageTypeSpecifier` describing the destination type, or `null`.
    See Also:
      - `setDestinationType(ImageTypeSpecifier)`

  - ### setDestinationOffset

    public void setDestinationOffset(Point destinationOffset)
    Specifies the offset in the destination image at which future decoded pixels are to be placed, when reading, or where a region will be written, when writing.

    When reading, the region to be written within the destination `BufferedImage` will start at this offset and have a width and height determined by the source region of interest, the subsampling parameters, and the destination bounds.

    Normal writes are not affected by this method, only writes performed using `ImageWriter.replacePixels`. For such writes, the offset specified is within the output stream image whose pixels are being modified.

    There is no `unsetDestinationOffset` method; simply call `setDestinationOffset(new Point(0, 0))` to restore default values.

    Parameters:
      `destinationOffset` - the offset in the destination, as a `Point`.
    Throws:
      `IllegalArgumentException` - if `destinationOffset` is `null`.
    See Also:
      - `getDestinationOffset()`
      - `ImageWriter.replacePixels(RenderedImage, ImageWriteParam)`

  - ### getDestinationOffset

    public Point getDestinationOffset()
    Returns the offset in the destination image at which pixels are to be placed.

    If `setDestinationOffsets` has not been called, a `Point` with zero X and Y values is returned (which is the correct value).

    Returns:
      the destination offset as a `Point`.
    See Also:
      - `setDestinationOffset(Point)`

  - ### setController

    public void setController(IIOParamController controller)
    Sets the `IIOParamController` to be used to provide settings for this `IIOParam` object when the `activateController` method is called, overriding any default controller. If the argument is `null`, no controller will be used, including any default. To restore the default, use `setController(getDefaultController())`.
    Parameters:
      `controller` - An appropriate `IIOParamController`, or `null`.
    See Also:
      - `IIOParamController`
      - `getController()`
      - `getDefaultController()`
      - `hasController()`
      - `activateController()`

  - ### getController

    public IIOParamController getController()
    Returns whatever `IIOParamController` is currently installed. This could be the default if there is one, `null`, or the argument of the most recent call to `setController`.
    Returns:
      the currently installed `IIOParamController`, or `null`.
    See Also:
      - `IIOParamController`
      - `setController(IIOParamController)`
      - `getDefaultController()`
      - `hasController()`
      - `activateController()`

  - ### getDefaultController

    public IIOParamController getDefaultController()
    Returns the default `IIOParamController`, if there is one, regardless of the currently installed controller. If there is no default controller, returns `null`.
    Returns:
      the default `IIOParamController`, or `null`.
    See Also:
      - `IIOParamController`
      - `setController(IIOParamController)`
      - `getController()`
      - `hasController()`
      - `activateController()`

  - ### hasController

    public boolean hasController()
    Returns `true` if there is a controller installed for this `IIOParam` object. This will return `true` if `getController` would not return `null`.
    Returns:
      `true` if a controller is installed.
    See Also:
      - `IIOParamController`
      - `setController(IIOParamController)`
      - `getController()`
      - `getDefaultController()`
      - `activateController()`

  - ### activateController

    public boolean activateController()
    Activates the installed `IIOParamController` for this `IIOParam` object and returns the resulting value. When this method returns `true`, all values for this `IIOParam` object will be ready for the next read or write operation. If `false` is returned, no settings in this object will have been disturbed (i.e., the user canceled the operation).

    Ordinarily, the controller will be a GUI providing a user interface for a subclass of `IIOParam` for a particular plug-in. Controllers need not be GUIs, however.

    Returns:
      `true` if the controller completed normally.
    Throws:
      `IllegalStateException` - if there is no controller currently installed.
    See Also:
      - `IIOParamController`
      - `setController(IIOParamController)`
      - `getController()`
      - `getDefaultController()`
      - `hasController()`