java.awt.image
Class RescaleOp

java.lang.Object
  java.awt.image.RescaleOp

All Implemented Interfaces:

BufferedImageOp, RasterOp

public class RescaleOp

extends Object

implements BufferedImageOp, RasterOp

This class performs a pixel-by-pixel rescaling of the data in the source image by multiplying the sample values for each pixel by a scale factor and then adding an offset. The scaled sample values are clipped to the minimum/maximum representable in the destination image.

The pseudo code for the rescaling operation is as follows:

for each pixel from Source object {
    for each band/component of the pixel {
        dstElement = (srcElement*scaleFactor) + offset
    }
}
 

For Rasters, rescaling operates on bands. The number of sets of scaling constants may be one, in which case the same constants are applied to all bands, or it must equal the number of Source Raster bands.

For BufferedImages, rescaling operates on color and alpha components. The number of sets of scaling constants may be one, in which case the same constants are applied to all color (but not alpha) components. Otherwise, the number of sets of scaling constants may equal the number of Source color components, in which case no rescaling of the alpha component (if present) is performed. If neither of these cases apply, the number of sets of scaling constants must equal the number of Source color components plus alpha components, in which case all color and alpha components are rescaled.

BufferedImage sources with premultiplied alpha data are treated in the same manner as non-premultiplied images for purposes of rescaling. That is, the rescaling is done per band on the raw data of the BufferedImage source without regard to whether the data is premultiplied. If a color conversion is required to the destination ColorModel, the premultiplied state of both source and destination will be taken into account for this step.

Images with an IndexColorModel cannot be rescaled.

If a RenderingHints object is specified in the constructor, the color rendering hint and the dithering hint may be used when color conversion is required.

Note that in-place operation is allowed (i.e. the source and destination can be the same object).

See Also:

RenderingHints.KEY_COLOR_RENDERING, RenderingHints.KEY_DITHERING

Field Summary

private int	dstNbits
(package private) RenderingHints	hints
(package private) int	length
(package private) float[]	offsets
(package private) float[]	scaleFactors
private int	srcNbits

Constructor Summary

RescaleOp(float[] scaleFactors, float[] offsets, RenderingHints hints)
Constructs a new RescaleOp with the desired scale factors and offsets.

RescaleOp(float scaleFactor, float offset, RenderingHints hints)
Constructs a new RescaleOp with the desired scale factor and offset.

Method Summary

private boolean	canUseLookup(Raster src, Raster dst) Determines if the rescale can be performed as a lookup.
private ByteLookupTable	createByteLut(float[] scale, float[] off, int nBands, int nElems) Creates a ByteLookupTable to implement the rescale.
BufferedImage	createCompatibleDestImage(BufferedImage src, ColorModel destCM) Creates a zeroed destination image with the correct size and number of bands.
WritableRaster	createCompatibleDestRaster(Raster src) Creates a zeroed-destination Raster with the correct size and number of bands, given this source.
private ShortLookupTable	createShortLut(float[] scale, float[] off, int nBands, int nElems) Creates a ShortLookupTable to implement the rescale.
BufferedImage	filter(BufferedImage src, BufferedImage dst) Rescales the source BufferedImage.
WritableRaster	filter(Raster src, WritableRaster dst) Rescales the pixel data in the source Raster.
Rectangle2D	getBounds2D(BufferedImage src) Returns the bounding box of the rescaled destination image.
Rectangle2D	getBounds2D(Raster src) Returns the bounding box of the rescaled destination Raster.
int	getNumFactors() Returns the number of scaling factors and offsets used in this RescaleOp.
float[]	getOffsets(float[] offsets) Returns the offsets in the given array.
Point2D	getPoint2D(Point2D srcPt, Point2D dstPt) Returns the location of the destination point given a point in the source.
RenderingHints	getRenderingHints() Returns the rendering hints for this op.
float[]	getScaleFactors(float[] scaleFactors) Returns the scale factors in the given array.

Methods inherited from class java.lang.Object

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

Field Detail

scaleFactors

float[] scaleFactors

offsets

float[] offsets

length

int length

hints

RenderingHints hints

srcNbits

private int srcNbits

dstNbits

private int dstNbits

Constructor Detail

RescaleOp

public RescaleOp(float[] scaleFactors,
                 float[] offsets,
                 RenderingHints hints)

Constructs a new RescaleOp with the desired scale factors and offsets. The length of the scaleFactor and offset arrays must meet the restrictions stated in the class comments above. The RenderingHints argument may be null.

Parameters:

scaleFactors - the specified scale factors

offsets - the specified offsets

hints - the specified RenderingHints, or null

RescaleOp

public RescaleOp(float scaleFactor,
                 float offset,
                 RenderingHints hints)

Constructs a new RescaleOp with the desired scale factor and offset. The scaleFactor and offset will be applied to all bands in a source Raster and to all color (but not alpha) components in a BufferedImage. The RenderingHints argument may be null.

Parameters:

scaleFactor - the specified scale factor

offset - the specified offset

hints - the specified RenderingHints, or null

Method Detail

getScaleFactors

public final float[] getScaleFactors(float[] scaleFactors)

Returns the scale factors in the given array. The array is also returned for convenience. If scaleFactors is null, a new array will be allocated.

Parameters:

scaleFactors - the array to contain the scale factors of this RescaleOp

Returns:

the scale factors of this RescaleOp.

getOffsets

public final float[] getOffsets(float[] offsets)

Returns the offsets in the given array. The array is also returned for convenience. If offsets is null, a new array will be allocated.

Parameters:

offsets - the array to contain the offsets of this RescaleOp

Returns:

the offsets of this RescaleOp.

getNumFactors

public final int getNumFactors()

Returns the number of scaling factors and offsets used in this RescaleOp.

Returns:

the number of scaling factors and offsets of this RescaleOp.

createByteLut

private ByteLookupTable createByteLut(float[] scale,
                                      float[] off,
                                      int nBands,
                                      int nElems)

Creates a ByteLookupTable to implement the rescale. The table may have either a SHORT or BYTE input.

Parameters:

nElems - Number of elements the table is to have. This will generally be 256 for byte and 65536 for short.

createShortLut

private ShortLookupTable createShortLut(float[] scale,
                                        float[] off,
                                        int nBands,
                                        int nElems)

Creates a ShortLookupTable to implement the rescale. The table may have either a SHORT or BYTE input.

Parameters:

nElems - Number of elements the table is to have. This will generally be 256 for byte and 65536 for short.

canUseLookup

private boolean canUseLookup(Raster src,
                             Raster dst)

Determines if the rescale can be performed as a lookup. The dst must be a byte or short type. The src must be less than 16 bits. All source band sizes must be the same and all dst band sizes must be the same.

filter

public final BufferedImage filter(BufferedImage src,
                                  BufferedImage dst)

Rescales the source BufferedImage. If the color model in the source image is not the same as that in the destination image, the pixels will be converted in the destination. If the destination image is null, a BufferedImage will be created with the source ColorModel. An IllegalArgumentException may be thrown if the number of scaling factors/offsets in this object does not meet the restrictions stated in the class comments above, or if the source image has an IndexColorModel.

Specified by:

filter in interface BufferedImageOp

Parameters:

src - the BufferedImage to be filtered

dst - the destination for the filtering operation or null

Returns:

the filtered BufferedImage.

Throws:

IllegalArgumentException - if the ColorModel of src is an IndexColorModel, or if the number of scaling factors and offsets in this RescaleOp do not meet the requirements stated in the class comments.

filter

public final WritableRaster filter(Raster src,
                                   WritableRaster dst)

Rescales the pixel data in the source Raster. If the destination Raster is null, a new Raster will be created. The source and destination must have the same number of bands. Otherwise, an IllegalArgumentException is thrown. Note that the number of scaling factors/offsets in this object must meet the restrictions stated in the class comments above. Otherwise, an IllegalArgumentException is thrown.

Specified by:

filter in interface RasterOp

Parameters:

src - the Raster to be filtered

dst - the destination for the filtering operation or null

Returns:

the filtered WritableRaster.

Throws:

IllegalArgumentException - if src and dst do not have the same number of bands, or if the number of scaling factors and offsets in this RescaleOp do not meet the requirements stated in the class comments.

getBounds2D

public final Rectangle2D getBounds2D(BufferedImage src)

Returns the bounding box of the rescaled destination image. Since this is not a geometric operation, the bounding box does not change.

Specified by:

getBounds2D in interface BufferedImageOp

Parameters:

src - The BufferedImage to be filtered

Returns:

The Rectangle2D representing the destination image's bounding box.

getBounds2D

public final Rectangle2D getBounds2D(Raster src)

Returns the bounding box of the rescaled destination Raster. Since this is not a geometric operation, the bounding box does not change.

Specified by:

getBounds2D in interface RasterOp

Parameters:

src - the rescaled destination Raster

Returns:

the bounds of the specified Raster.

createCompatibleDestImage

public BufferedImage createCompatibleDestImage(BufferedImage src,
                                               ColorModel destCM)

Creates a zeroed destination image with the correct size and number of bands.

Specified by:

createCompatibleDestImage in interface BufferedImageOp

Parameters:

src - Source image for the filter operation.

destCM - ColorModel of the destination. If null, the ColorModel of the source will be used.

Returns:

the zeroed-destination image.

createCompatibleDestRaster

public WritableRaster createCompatibleDestRaster(Raster src)

Creates a zeroed-destination Raster with the correct size and number of bands, given this source.

Specified by:

createCompatibleDestRaster in interface RasterOp

Parameters:

src - the source Raster

Returns:

the zeroed-destination Raster.

getPoint2D

public final Point2D getPoint2D(Point2D srcPt,
                                Point2D dstPt)

Returns the location of the destination point given a point in the source. If dstPt is non-null, it will be used to hold the return value. Since this is not a geometric operation, the srcPt will equal the dstPt.

Specified by:

getPoint2D in interface BufferedImageOp

Parameters:

srcPt - a point in the source image

dstPt - the destination point or null

Returns:

the location of the destination point.

getRenderingHints

public final RenderingHints getRenderingHints()

Returns the rendering hints for this op.

Specified by:

getRenderingHints in interface BufferedImageOp

Returns:

the rendering hints of this RescaleOp.