| java.lang.Object
 javax.imageio.IIOParam
javax.imageio.ImageReadParam
All known Subclasses: javax.imageio.plugins.jpeg.JPEGImageReadParam,
| ImageReadParam | | public class ImageReadParam extends IIOParam (Code) | | A class describing how a stream is to be decoded. Instances of
this class or its subclasses are used to supply prescriptive
"how-to" information to instances of ImageReader.
An image encoded as part of a file or stream may be thought of
extending out in multiple dimensions: the spatial dimensions of
width and height, a number of bands, and a number of progressive
decoding passes. This class allows a contiguous (hyper)rectangular
subarea of the image in all of these dimensions to be selected for
decoding. Additionally, the spatial dimensions may be subsampled
discontinuously. Finally, color and format conversions may be
specified by controlling the ColorModel and
SampleModel of the destination image, either by
providing a BufferedImage or by using an
ImageTypeSpecifier.
An ImageReadParam object is used to specify how an
image, or a set of images, will be converted on input from
a stream in the context of the Java Image I/O framework. A plug-in for a
specific image format will return instances of
ImageReadParam from the
getDefaultReadParam method of its
ImageReader implementation.
The state maintained by an instance of
ImageReadParam is independent of any particular image
being decoded. When actual decoding takes place, the values set in
the read param are combined with the actual properties of the image
being decoded from the stream and the destination
BufferedImage that will receive the decoded pixel
data. For example, the source region set using
setSourceRegion will first be intersected with the
actual valid source area. The result will be translated by the
value returned by getDestinationOffset, and the
resulting rectangle intersected with the actual valid destination
area to yield the destination area that will be written.
The parameters specified by an ImageReadParam are
applied to an image as follows. First, if a rendering size has
been set by setSourceRenderSize, the entire decoded
image is rendered at the size given by
getSourceRenderSize. Otherwise, the image has its
natural size given by ImageReader.getWidth and
ImageReader.getHeight.
Next, the image is clipped against the source region
specified by getSourceXOffset, getSourceYOffset,
getSourceWidth, and getSourceHeight.
The resulting region is then subsampled according to the
factors given in
IIOParam.setSourceSubsampling IIOParam.setSourceSubsampling . The first pixel,
the number of pixels per row, and the number of rows all depend
on the subsampling settings.
Call the minimum X and Y coordinates of the resulting rectangle
(minX, minY), its width w
and its height h.
This rectangle is offset by
(getDestinationOffset().x,
getDestinationOffset().y) and clipped against the
destination bounds. If no destination image has been set, the
destination is defined to have a width of
getDestinationOffset().x + w, and a
height of getDestinationOffset().y + h so
that all pixels of the source region may be written to the
destination.
Pixels that land, after subsampling, within the destination
image, and that are written in one of the progressive passes
specified by getSourceMinProgressivePass and
getSourceNumProgressivePasses are passed along to the
next step.
Finally, the source samples of each pixel are mapped into
destination bands according to the algorithm described in the
comment for setDestinationBands.
Plug-in writers may extend the functionality of
ImageReadParam by providing a subclass that implements
additional, plug-in specific interfaces. It is up to the plug-in
to document what interfaces are available and how they are to be
used. Readers will silently ignore any extended features of an
ImageReadParam subclass of which they are not aware.
Also, they may ignore any optional features that they normally
disable when creating their own ImageReadParam
instances via getDefaultReadParam.
Note that unless a query method exists for a capability, it must
be supported by all ImageReader implementations
(e.g. source render size is optional, but subsampling must be
supported).
version:
0.5
See Also: ImageReader
See Also: ImageWriter
See Also: ImageWriteParam |
| Field Summary | |
| protected boolean | canSetSourceRenderSize
true if this ImageReadParam allows
the source rendering dimensions to be set. | | protected BufferedImage | destination
The current destination BufferedImage, or
null if none has been set. | | protected int[] | destinationBands
The set of destination bands to be used, as an array of
ints. | | protected int | minProgressivePass
The minimum index of a progressive pass to read from the
source. | | protected int | numProgressivePasses
The maximum number of progressive passes to read from the
source. | | protected Dimension | sourceRenderSize
The desired rendering width and height of the source, if
canSetSourceRenderSize is true, or
null. |
| Constructor Summary | |
| public | ImageReadParam()
Constructs an ImageReadParam. |
| Method Summary | |
| public boolean | canSetSourceRenderSize()
Returns true if this reader allows the source
image to be rendered at an arbitrary size as part of the
decoding process, by means of the
setSourceRenderSize method. | | public BufferedImage | getDestination()
Returns the BufferedImage currently set by the
setDestination method, or null
if none is set. | | public int[] | getDestinationBands()
Returns the set of band indices where data will be placed. | | public int | getSourceMaxProgressivePass()
If getSourceNumProgressivePasses is equal to
Integer.MAX_VALUE, returns
Integer.MAX_VALUE. | | public int | getSourceMinProgressivePass()
Returns the index of the first progressive pass that will be
decoded. | | public int | getSourceNumProgressivePasses()
Returns the number of the progressive passes that will be
decoded. | | public Dimension | getSourceRenderSize()
Returns the width and height of the source image as it
will be rendered during decoding, if they have been set via the
setSourceRenderSize method. | | public void | setDestination(BufferedImage destination)
Supplies a BufferedImage to be used as the
destination for decoded pixel data. | | public void | setDestinationBands(int[] destinationBands)
Sets the indices of the destination bands where data
will be placed. | | public void | setDestinationType(ImageTypeSpecifier destinationType)
| | public void | setSourceProgressivePasses(int minPass, int numPasses)
Sets the range of progressive passes that will be decoded.
Passes outside of this range will be ignored.
A progressive pass is a re-encoding of the entire image,
generally at progressively higher effective resolutions, but
requiring greater transmission bandwidth. | | public void | setSourceRenderSize(Dimension size)
If the image is able to be rendered at an arbitrary size, sets
the source width and height to the supplied values. |
| canSetSourceRenderSize | | protected boolean canSetSourceRenderSize(Code) | | true if this ImageReadParam allows
the source rendering dimensions to be set. By default, the
value is false. Subclasses must set this value
manually.
ImageReaders that do not support setting of
the source render size should set this value to
false.
|
| destination | | protected BufferedImage destination(Code) | | The current destination BufferedImage, or
null if none has been set. By default, the value
is null.
|
| destinationBands | | protected int[] destinationBands(Code) | | The set of destination bands to be used, as an array of
ints. By default, the value is null,
indicating all destination bands should be written in order.
|
| minProgressivePass | | protected int minProgressivePass(Code) | | The minimum index of a progressive pass to read from the
source. By default, the value is set to 0, which indicates
that passes starting with the first available pass should be
decoded.
Subclasses should ensure that this value is
non-negative.
|
| numProgressivePasses | | protected int numProgressivePasses(Code) | | The maximum number of progressive passes to read from the
source. By default, the value is set to
Integer.MAX_VALUE, which indicates that passes up
to and including the last available pass should be decoded.
Subclasses should ensure that this value is positive.
Additionally, if the value is not
Integer.MAX_VALUE, then minProgressivePass +
numProgressivePasses - 1 should not exceed
Integer.MAX_VALUE.
|
| sourceRenderSize | | protected Dimension sourceRenderSize(Code) | | The desired rendering width and height of the source, if
canSetSourceRenderSize is true, or
null.
ImageReaders that do not support setting of
the source render size may ignore this value.
|
| ImageReadParam | | public ImageReadParam()(Code) | | Constructs an ImageReadParam.
|
| canSetSourceRenderSize | | public boolean canSetSourceRenderSize()(Code) | | Returns true if this reader allows the source
image to be rendered at an arbitrary size as part of the
decoding process, by means of the
setSourceRenderSize method. If this method
returns false, calls to
setSourceRenderSize will throw an
UnsupportedOperationException.
true if setting source rendering size issupported.
See Also: ImageReadParam.setSourceRenderSize |
| getDestinationBands | | public int[] getDestinationBands()(Code) | | Returns the set of band indices where data will be placed.
If no value has been set, null is returned to
indicate that all destination bands will be used.
the indices of the destination bands to be used,or null.
See Also: ImageReadParam.setDestinationBands |
| getSourceMaxProgressivePass | | public int getSourceMaxProgressivePass()(Code) | | If getSourceNumProgressivePasses is equal to
Integer.MAX_VALUE, returns
Integer.MAX_VALUE. Otherwise, returns
getSourceMinProgressivePass() +
getSourceNumProgressivePasses() - 1.
the index of the last pass to be read, orInteger.MAX_VALUE. |
| getSourceRenderSize | | public Dimension getSourceRenderSize()(Code) | | Returns the width and height of the source image as it
will be rendered during decoding, if they have been set via the
setSourceRenderSize method. A
nullvalue indicates that no setting has been made.
the rendered width and height of the source imageas a Dimension.
See Also: ImageReadParam.setSourceRenderSize |
| setDestination | | public void setDestination(BufferedImage destination)(Code) | | Supplies a BufferedImage to be used as the
destination for decoded pixel data. The currently set image
will be written to by the read,
readAll, and readRaster methods, and
a reference to it will be returned by those methods.
Pixel data from the aforementioned methods will be written
starting at the offset specified by
getDestinationOffset.
If destination is null, a
newly-created BufferedImage will be returned by
those methods.
At the time of reading, the image is checked to verify that
its ColorModel and SampleModel
correspond to one of the ImageTypeSpecifiers
returned from the ImageReader's
getImageTypes method. If it does not, the reader
will throw an IIOException.
Parameters:
destination - the BufferedImage to be written to, ornull.
See Also: ImageReadParam.getDestination |
| setDestinationBands | | public void setDestinationBands(int[] destinationBands)(Code) | | Sets the indices of the destination bands where data
will be placed. Duplicate indices are not allowed.
A null value indicates that all destination
bands will be used.
Choosing a destination band subset will not affect the
number of bands in the output image of a read if no destination
image is specified; the created destination image will still
have the same number of bands as if this method had never been
called. If a different number of bands in the destination
image is desired, an image must be supplied using the
ImageReadParam.setDestination method.
At the time of reading or writing, an
IllegalArgumentException will be thrown by the
reader or writer if a value larger than the largest destination
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.
Parameters:
destinationBands - an array of integer band indices to beused.
exception:
IllegalArgumentException - if destinationBandscontains a negative or duplicate value.
See Also: ImageReadParam.getDestinationBands
See Also: ImageReadParam.getSourceBands
See Also: ImageReader.checkReadParamBandSettings |
| setSourceProgressivePasses | | public void setSourceProgressivePasses(int minPass, int numPasses)(Code) | | Sets the range of progressive passes that will be decoded.
Passes outside of this range will be ignored.
A progressive pass is a re-encoding of the entire image,
generally at progressively higher effective resolutions, but
requiring greater transmission bandwidth. The most common use
of progressive encoding is found in the JPEG format, where
successive passes include more detailed representations of the
high-frequency image content.
The actual number of passes to be decoded is determined
during decoding, based on the number of actual passes available
in the stream. Thus if minPass + numPasses - 1 is
larger than the index of the last available passes, decoding
will end with that pass.
A value of numPasses of
Integer.MAX_VALUE indicates that all passes from
minPass forward should be read. Otherwise, the
index of the last pass (i.e., minPass + numPasses
- 1) must not exceed Integer.MAX_VALUE.
There is no unsetSourceProgressivePasses
method; the same effect may be obtained by calling
setSourceProgressivePasses(0, Integer.MAX_VALUE).
Parameters:
minPass - the index of the first pass to be decoded.
Parameters:
numPasses - the maximum number of passes to be decoded.
exception:
IllegalArgumentException - if minPass isnegative, numPasses is negative or 0, ornumPasses is smaller thanInteger.MAX_VALUE but minPass +numPasses - 1 is greater thanINTEGER.MAX_VALUE.
See Also: ImageReadParam.getSourceMinProgressivePass
See Also: ImageReadParam.getSourceMaxProgressivePass |
| setSourceRenderSize | | public void setSourceRenderSize(Dimension size) throws UnsupportedOperationException(Code) | | If the image is able to be rendered at an arbitrary size, sets
the source width and height to the supplied values. Note that
the values returned from the getWidth and
getHeight methods on ImageReader are
not affected by this method; they will continue to return the
default size for the image. Similarly, if the image is also
tiled the tile width and height are given in terms of the default
size.
Typically, the width and height should be chosen such that
the ratio of width to height closely approximates the aspect
ratio of the image, as returned from
ImageReader.getAspectRatio.
If this plug-in does not allow the rendering size to be
set, an UnsupportedOperationException will be
thrown.
To remove the render size setting, pass in a value of
null for size.
Parameters:
size - a Dimension indicating the desiredwidth and height.
exception:
IllegalArgumentException - if either the width or theheight is negative or 0.
exception:
UnsupportedOperationException - if image resizingis not supported by this plug-in.
See Also: ImageReadParam.getSourceRenderSize
See Also: ImageReader.getWidth
See Also: ImageReader.getHeight
See Also: ImageReader.getAspectRatio |
|
|
