📄 geometric image manipulation.htm
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images geometrically. The translation is often carried out to align the images
before performing a combination operation, such as image addition,
subtraction, division, or compositing.
<P><A name=73212>
<HR>
<CENTER><IMG
src="Geometric Image Manipulation.files/Geom-image-manip.doc.anc36.gif"></CENTER>
<HR>
</A><A name=73213>
<CENTER><FONT size=-1><B><I>Figure 8-4 </I><IMG
src="Geometric Image Manipulation.files/sm-blank.gif" border=0> Translate
Operation</B></FONT></CENTER></A>
<P>The <CODE>translate</CODE> operation takes one rendered or renderable
source image and three parameters:
<P>
<TABLE cellPadding=3 border=3>
<CAPTION><FONT size=-1><B></B></FONT></CAPTION>
<TBODY>
<TR vAlign=top>
<TH><A name=60889>Parameters </A>
<TH><A name=60891>Type </A>
<TH><A name=60893>Description </A>
<TR vAlign=top>
<TD><A name=60895>xTrans</A><BR>
<TD><A name=60897>Float</A><BR>
<TD><A name=60899>The displacement in the <EM>x</EM> direction. The
default value is 0.0F.</A><BR>
<TR vAlign=top>
<TD><A name=60901>yTrans</A><BR>
<TD><A name=60903>Float</A><BR>
<TD><A name=60905>The displacement in the <EM>y</EM> direction. The
default value is 0.0F.</A><BR>
<TR vAlign=top>
<TD><A name=60907>interpolation</A><BR>
<TD><A name=60909>Interpolation</A><BR>
<TD><A name=61259>The interpolation method for resampling. One of
INTERP_NEAREST, INTERP_BILINEAR, INTERP_BICUBIC, or INTERP_BICUBIC2. The
default value is null.</A><BR></TR></TBODY></TABLE>
<P>The <CODE>xTrans</CODE> parameter corresponds to <EM>t</EM><SUB>x</SUB> and
the <CODE>yTrans</CODE> parameter corresponds to <EM>t</EM><SUB>y</SUB> in <A
href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Geom-image-manip.doc.html#60873">equation
8.1</A>. If <CODE>xTrans</CODE> is positive, the translation is to the right;
if negative, to the left. If <CODE>yTrans</CODE> is positive, the translation
is down; if negative, upward. If both <CODE>xTrans</CODE> and
<CODE>yTrans</CODE> are integral, the operation simply <EM>wraps</EM> its
source image to change the image's position in the coordinate plane.
<P>When interpolations that require padding the source such as bilinear or
bicubic interpolation are specified, the boundary of the source image needs to
be extended such that it has the extra pixels needed to compute all the
destination pixels. This extension is performed via the
<CODE>BorderExtender</CODE> class. The type of border extension can be
specified as a <CODE>RenderingHint</CODE> to the <CODE>JAI.create</CODE>
method. If no border extension type is provided, a default extension of
<CODE>BorderExtender.BORDER_COPY</CODE> will be used to perform the extension.
See <A
href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Programming-environ.doc.html#55991">Section
3.7.3, "Rendering Hints</A>."
<P><A
href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Geom-image-manip.doc.html#69434">Listing
8-2</A> shows a code sample for a translate operation using nearest-neighbor
interpolation.
<P><CAPTION><FONT size=-1><B><A name=69434>
<CENTER><FONT size=-1><B><I>Listing 8-2 </I><IMG
src="Geometric Image Manipulation.files/sm-blank.gif" border=0> Example
Translate Operation</B></FONT></CENTER></A>
<P></B></FONT></CAPTION>
<HR>
<TR valign="top"><TD><PRE> // Create a ParameterBlock and specify the source and
// parameters.
ParameterBlock pb = new ParameterBlock();
pb.addSource(im); // The source image
pb.add((float)Math.max(-mx, 0)); // The x translation
pb.add((float)Math.max(-my, 0)); // The y translation
pb.add(new InterpolationNearest()); // The interpolation
</PRE><TR valign="top"><TD><PRE> // Create the translate operation
im = JAI.create("translate", pb, null);
</PRE>
<HR>
<P><A name=60938>
<H3>8.3.2 <IMG src="Geometric Image Manipulation.files/space.gif">Scaling
Transformation</H3></A>Scaling, also known as <EM>minification</EM> and
<EM>magnification</EM>, enlarges or shrinks an image. An <EM>x</EM>-value
defines the amount of scaling in the <EM>x</EM> direction, and a
<EM>y</EM>-value defines the amount of scaling in the <EM>y</EM> direction.
The <CODE>Scale</CODE> operation both translates and resizes.
<P>Scaling is often used to geometrically register multiple images prior to
performing a combination operation, such as image addition, subtraction,
division, or compositing. Scaling can also be used to correct geometric
distortions introduced in the image acquisition process, although the
<CODE>Affine</CODE> operation (<A
href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Geom-image-manip.doc.html#51275">"Affine
Transformation" on page 272</A>) would be more suitable for this.
<P>For each pixel (<EM>x</EM>, <EM>y</EM>) of the destination, the source
value at the fractional subpixel position is constructed by means of an
<CODE>Interpolation</CODE> object and written to the destination.
<P>
<DL><A name=60948>
<DT>
<DD><IMG
src="Geometric Image Manipulation.files/Geom-image-manip.doc.anc6.gif"> </A>
<P></P></DD></DL>The <CODE>scale</CODE> operation takes one rendered or
renderable source image and five parameters:
<P>
<TABLE cellPadding=3 border=3>
<CAPTION><FONT size=-1><B></B></FONT></CAPTION>
<TBODY>
<TR vAlign=top>
<TH><A name=60951>Parameters </A>
<TH><A name=60953>Type </A>
<TH><A name=60955>Description </A>
<TR vAlign=top>
<TD><A name=60957>xScale</A><BR>
<TD><A name=60959>Float</A><BR>
<TD><A name=60961>The <EM>x</EM> scale factor.</A><BR>
<TR vAlign=top>
<TD><A name=60963>yScale</A><BR>
<TD><A name=60965>Float</A><BR>
<TD><A name=60967>The <EM>y</EM> scale factor.</A><BR>
<TR vAlign=top>
<TD><A name=60969>xTrans</A><BR>
<TD><A name=60971>Float</A><BR>
<TD><A name=60973>The <EM>x</EM> translation.</A><BR>
<TR vAlign=top>
<TD><A name=60975>xTrans</A><BR>
<TD><A name=60977>Float</A><BR>
<TD><A name=60979>The <EM>y</EM> translation.</A><BR>
<TR vAlign=top>
<TD><A name=60981>interpolation</A><BR>
<TD><A name=60983>Interpolation</A><BR>
<TD><A name=60985>The interpolation method for resampling. One of
INTERP_NEAREST, INTERP_BILINEAR, INTERP_BICUBIC, or
INTERP_BICUBIC2.</A><BR></TR></TBODY></TABLE>
<P>When applying scale factors (<CODE>xScale</CODE> and <CODE>yScale</CODE>)
to a source image with width of <CODE>src_width</CODE> and height of
<CODE>src_height</CODE>, the resulting image is defined to have the following
dimensions:
<P><PRE> dst_width = src_width * xScale
dst_height = src_height * yScale
</PRE>Scale factors greater than 1.0 magnify the image; less than 1.0 minify
the image. The <CODE>xTrans</CODE> parameter corresponds to
<EM>t</EM><SUB>x</SUB> and the <CODE>yTrans</CODE> parameter corresponds to
<EM>t</EM><SUB>y</SUB> in <A
href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Geom-image-manip.doc.html#60873">equation
8.1</A>. If <CODE>xTrans</CODE> is positive, the translation is to the right;
if negative, to the left. If <CODE>yTrans</CODE> is positive, the translation
is down; if negative, upward.
<P><A name=73168>
<HR>
<CENTER><IMG
src="Geometric Image Manipulation.files/Geom-image-manip.doc.anc25.gif"></CENTER>
<HR>
</A><A name=73169>
<CENTER><FONT size=-1><B><I>Figure 8-5 </I><IMG
src="Geometric Image Manipulation.files/sm-blank.gif" border=0> Scale
Operation</B></FONT></CENTER></A>
<P>When interpolations that require padding the source such as Bilinear or
Bicubic interpolation are specified, the boundary of the source image needs to
be extended such that it has the extra pixels needed to compute all the
destination pixels. This extension is performed via the
<CODE>BorderExtender</CODE> class. The type of border extension can be
specified as a <CODE>RenderingHint</CODE> to the <CODE>JAI.create</CODE>
method. See <A
href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Programming-environ.doc.html#55991">Section
3.7.3, "Rendering Hints</A>."
<P>If no Border Extension is specified, the source will not be extended. The
scaled image size is still calculated according to the equation specified
above. However since there isn't enough source to compute all the destination
pixels, only that subset of the destination image's pixels that can be
computed will be written in the destination. The rest of the destination will
not be written.
<P><A
href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Geom-image-manip.doc.html#69465">Listing
8-3</A> shows a code sample for a <CODE>Scale</CODE> operation using a scale
factor of 1.2 and nearest-neighbor interpolation.
<P><CAPTION><FONT size=-1><B><A name=69465>
<CENTER><FONT size=-1><B><I>Listing 8-3 </I><IMG
src="Geometric Image Manipulation.files/sm-blank.gif" border=0> Example Scale
Operation</B></FONT></CENTER></A>
<P></B></FONT></CAPTION>
<HR>
<TR valign="top"><TD><PRE> // Create a ParameterBlock and specify the source and
// parameters
ParameterBlock pb = new ParameterBlock();
pb.addSource(im); // The source image
pb.add(1.2); // The xScale
pb.add(1.2); // The yScale
pb.add(0.0F); // The x translation
pb.add(0.0F); // The y translation
pb.add(new InterpolationNearest()); // The interpolation
</PRE><TR valign="top"><TD><PRE> // Create the scale operation
im = JAI.create("scale", pb, null);
</PRE>
<HR>
<P><A name=61009>
<H3>8.3.3 <IMG src="Geometric Image Manipulation.files/space.gif">Rotation
Transformation</H3></A>The <CODE>rotate</CODE> operation rotates an image
about a given point by a given angle. Specified <EM>x</EM> and <EM>y</EM>
values define the coordinate of the source image about which to rotate the
image and a rotation angle in <EM>radians</EM> defines the angle of rotation
about the rotation point. If no rotation point is specified, a default of
(0,0) is assumed.
<P>A negative rotation value rotates the image counter-clockwise, while a
positive rotation value rotates the image clockwise.
<P><A name=73109>
<HR>
<CENTER><IMG
src="Geometric Image Manipulation.files/Geom-image-manip.doc.ancA20.gif"></CENTER>
<HR>
</A><A name=73110>
<CENTER><FONT size=-1><B><I>Figure 8-6 </I><IMG
src="Geometric Image Manipulation.files/sm-blank.gif" border=0> Rotate
Operation</B></FONT></CENTER></A>
<P>The <CODE>rotate</CODE> operation takes one rendered or renderable source
image and four parameters:
<P>
<TABLE cellPadding=3 border=3>
<CAPTION><FONT size=-1><B></B></FONT></CAPTION>
<TBODY>
<TR vAlign=top>
<TH><A name=68407>Parameters </A>
<TH><A name=68409>Type </A>
<TH><A name=68411>Description </A>
<TR vAlign=top>
<TD><A name=68413>xOrigin</A><BR>
<TD><A name=68415>Float</A><BR>
<TD><A name=68417>The <EM>x</EM> origin to rotate about.</A><BR>
<TR vAlign=top>
<TD><A name=68419>yOrigin</A><BR>
<TD><A name=68421>Float</A><BR>
<TD><A name=68423>The <EM>y</EM> origin to rotate about.</A><BR>
<TR vAlign=top>
<TD><A name=68425>angle</A><BR>
<TD><A name=68427>Float</A><BR>
<TD><A name=68429>The rotation angle in radians.</A><BR>
<TR vAlign=top>
<TD><A name=68431>interpolation</A><BR>
<TD><A name=68433>Interpolation</A><BR>
<TD><A name=68435>The interpolation method for resampling. One of
INTERP_NEAREST, INTERP_BILINEAR, INTERP_BICUBIC, or
INTERP_BICUBIC2.</A><BR></TR></TBODY></TABLE>
<P>When interpolations that require padding the source such as Bilinear or
Bicubic interpolation are specified, the boundary of the source image needs to
be extended such that it has the extra pixels needed to compute all the
destination pixels. This extension is performed via the
<CODE>BorderExtender</CODE> class. The type of border extension can be
specified as a <CODE>RenderingHint</CODE> to the <CODE>JAI.create</CODE>
method. If no border extension type is provided, a default extension of
<CODE>BorderExtender.BORDER_COPY</CODE> will be used to perform the extension.
See <A
href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Programming-environ.doc.html#55991">Section
3.7.3, "Rendering Hints</A>."
<P><A
href="http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Geom-image-manip.doc.html#69491">Listing
8-4</A> shows a code sample for a <CODE>Rotate</CODE> operation for a rotation
angle of 45 degrees. Since the rotation angle must be specified in radians,
the example first converts 45 degrees to radians.
<P><CAPTION><FONT size=-1><B><A name=69491>
<CENTER><FONT size=-1><B><I>Listing 8-4 </I><IMG
src="Geometric Image Manipulation.files/sm-blank.gif" border=0> Example Rotate
Operation </B></FONT></CENTER></A>
<P></B></FONT></CAPTION>
<HR>
<TR valign="top"><TD><PRE> // Create the rotation a⌨️ 快捷键说明
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