Java Doc for ScaleOpImage.java in  » 6.0-JDK-Modules » Java-Advanced-Imaging » javax » media » jai » Java Source Code / Java DocumentationJava Source Code and Java Documentation

When applying scale factors of scaleX, scaleY to a source image with the upper left pixel at (srcMinX, srcMinY) and width of srcWidth and height of srcHeight, the resulting image is defined to have the following bounds: dstMinX = ceil(A), where A = srcMinX * scaleX - 0.5 + transX, dstMinY = ceil(B), where B = srcMinY * scaleY - 0.5 + transY, dstMaxX = ceil(C), where C = (srcMaxX + 1) * scaleX - 1.5 + transX and srcMaxX = srcMinX + srcWidth - 1 dstMaxY = ceil(D), where D = (srcMaxY + 1) * scaleY - 1.5 + transY and srcMaxY = srcMinY + srcHeight - 1 dstWidth = dstMaxX - dstMinX + 1 dstHeight = dstMaxY - dstMinY + 1

In the case where source's upper left pixel is located is (0, 0), the formulae simplify to dstMinX = 0 dstMinY = 0 dstWidth = ceil (srcWidth * scaleX - 0.5 + transX) dstHeight = ceil (srcHeight * scaleY - 0.5 + transY)

In the case where the source's upper left pixel is located at (0, 0) and the scaling factors are integers, the formulae further simplify to dstMinX = 0 dstMinY = 0 dstWidth = ceil (srcWidth * scaleX + transX) dstWidth = ceil (srcHeight * scaleY + transY)

When interpolations which require padding the source such as Bilinear or Bicubic interpolation are specified, the source needs to be extended such that it has the extra pixels needed to compute all the destination pixels. This extension is performed via the BorderExtender class. The type of border extension can be specified as a RenderingHint to the JAI.create method.

If no BorderExtender is specified, the source will not be extended. The scaled image size is still calculated according to the formula specified above. However since there is not enough source to compute all the destination pixels, only that subset of the destination image's pixels which can be computed, will be written in the destination. The rest of the destination will be set to zeros.

It may be noted that the minX, minY, width and height hints as specified through the JAI.KEY_IMAGE_LAYOUT hint in the RenderingHints object are not honored, as this operator calculates the destination image bounds itself. The other ImageLayout hints, like tileWidth and tileHeight, however are honored. It should be noted that the superclass GeometricOpImage automatically adds a value of Boolean.TRUE for the JAI.KEY_REPLACE_INDEX_COLOR_MODEL to the given configuration and passes it up to its superclass constructor so that geometric operations are performed on the pixel values instead of being performed on the indices into the color map for those operations whose source(s) have an IndexColorModel. This addition will take place only if a value for the JAI.KEY_REPLACE_INDEX_COLOR_MODEL has not already been provided by the user. Note that the configuration Map is cloned before the new hint is added to it. Regarding the value for the JAI.KEY_REPLACE_INDEX_COLOR_MODEL RenderingHints, the operator itself can be smart based on the parameters, i.e. while the default value for the JAI.KEY_REPLACE_INDEX_COLOR_MODEL is Boolean.TRUE for operations that extend this class, in some cases the operator could set the default.
See Also:   WarpOpImage
See Also:   OpImage

The implementation in this class returns the value of pt in the following code snippet:

 Point2D pt = (Point2D)destPt.clone();
 pt.setLocation((destPt.getX() - transX + 0.5)/scaleX - 0.5,
 (destPt.getY() - transY + 0.5)/scaleY - 0.5);
 

The implementation in this class returns the value of pt in the following code snippet:

 Point2D pt = (Point2D)sourcePt.clone();
 pt.setLocation(scaleX*(sourcePt.getX() + 0.5) + transX - 0.5,
 scaleY*(sourcePt.getY() + 0.5) + transY - 0.5);
 

The Rational approximation is valid upto the sixth decimal place.
Parameters:
  layout - an ImageLayout optionally containingthe tile grid layout, SampleModel, andColorModel, or null.
Parameters:
  source - a RenderedImage.
Parameters:
  configuration - Configurable attributes of the image includingconfiguration variables indexed byRenderingHints.Keys and image properties indexedby Strings or CaselessStringKeys.This is simply forwarded to the superclass constructor.
Parameters:
  cobbleSources - a boolean indicating whethercomputeRect expects contiguous sources.
Parameters:
  extender - a BorderExtender, or null.
Parameters:
  interp - an Interpolation object to use forresampling.
Parameters:
  scaleX - scale factor along x axis.
Parameters:
  scaleY - scale factor along y axis.
Parameters:
  transX - translation factor along x axis.
Parameters:
  transY - translation factor along y axis.
throws:
  IllegalArgumentException - if sourceis null.
throws:
  IllegalArgumentException - if combining thesource bounds with the layout parameter results in negativeoutput width or height.
since:
   JAI 1.1

The image bounds may be larger than the bounds of the source image. In this case, samples for which there are no corresponding sources are set to zero.

The following steps are performed in order to compute the tile:

• The destination tile is backward mapped to compute the needed source.
• This source is then split on tile boundaries to produce rectangles that do not cross tile boundaries.
• These source rectangles are then forward mapped to produce destination rectangles, and the computeRect method is called for each corresponding pair of source and destination rectangles.
• For higher order interpolations, some source cobbling across tile boundaries does occur.

The implementation in this class returns the value of pt in the following code snippet:

 Point2D pt = (Point2D)destPt.clone();
 pt.setLocation((destPt.getX() - transX + 0.5)/scaleX - 0.5,
 (destPt.getY() - transY + 0.5)/scaleY - 0.5);
 

The implementation in this class returns the value of pt in the following code snippet:

 Point2D pt = (Point2D)sourcePt.clone();
 pt.setLocation(scaleX*(sourcePt.getX() + 0.5) + transX - 0.5,
 scaleY*(sourcePt.getY() + 0.5) + transY - 0.5);