Module java.desktop
Package 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:

  • Constructor Details

    • 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 Details

    • 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.

    • 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, or if the source and destination images differ in size.

    • 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, or if the source and destination rasters differ in size.

    • 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
      Specified by:
      getPoint2D in interface RasterOp
      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
      Specified by:
      getRenderingHints in interface RasterOp
      Returns:
      the rendering hints of this RescaleOp.