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6829673: ThinLineTest: A line < 1 pixel disappears

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Reviewed-by: igor, prr
This commit is contained in:
Roman Kennke 2009-08-04 17:25:36 -07:00 committed by Jennifer Godinez
parent 430c84f1ea
commit 63e666407c
2 changed files with 131 additions and 2 deletions
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70
jdk/src/share/classes/sun/java2d/pisces/PiscesRenderingEngine.java
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@ -171,9 +171,9 @@ public class PiscesRenderingEngine extends RenderingEngine {
float lw;
if (thin) {
if (antialias) {
lw = 0.5f;
lw = userSpaceLineWidth(at, 0.5f);
} else {
lw = 1.0f;
lw = userSpaceLineWidth(at, 1.0f);
}
} else {
lw = bs.getLineWidth();
@ -189,6 +189,72 @@ public class PiscesRenderingEngine extends RenderingEngine {
lsink);
}
private float userSpaceLineWidth(AffineTransform at, float lw) {
double widthScale;
if ((at.getType() & (AffineTransform.TYPE_GENERAL_TRANSFORM |
AffineTransform.TYPE_GENERAL_SCALE)) != 0) {
widthScale = Math.sqrt(at.getDeterminant());
} else {
/* First calculate the "maximum scale" of this transform. */
double A = at.getScaleX(); // m00
double C = at.getShearX(); // m01
double B = at.getShearY(); // m10
double D = at.getScaleY(); // m11
/*
* Given a 2 x 2 affine matrix [ A B ] such that
* [ C D ]
* v' = [x' y'] = [Ax + Cy, Bx + Dy], we want to
* find the maximum magnitude (norm) of the vector v'
* with the constraint (x^2 + y^2 = 1).
* The equation to maximize is
* |v'| = sqrt((Ax+Cy)^2+(Bx+Dy)^2)
* or |v'| = sqrt((AA+BB)x^2 + 2(AC+BD)xy + (CC+DD)y^2).
* Since sqrt is monotonic we can maximize |v'|^2
* instead and plug in the substitution y = sqrt(1 - x^2).
* Trigonometric equalities can then be used to get
* rid of most of the sqrt terms.
*/
double EA = A*A + B*B; // x^2 coefficient
double EB = 2*(A*C + B*D); // xy coefficient
double EC = C*C + D*D; // y^2 coefficient
/*
* There is a lot of calculus omitted here.
*
* Conceptually, in the interests of understanding the
* terms that the calculus produced we can consider
* that EA and EC end up providing the lengths along
* the major axes and the hypot term ends up being an
* adjustment for the additional length along the off-axis
* angle of rotated or sheared ellipses as well as an
* adjustment for the fact that the equation below
* averages the two major axis lengths. (Notice that
* the hypot term contains a part which resolves to the
* difference of these two axis lengths in the absence
* of rotation.)
*
* In the calculus, the ratio of the EB and (EA-EC) terms
* ends up being the tangent of 2*theta where theta is
* the angle that the long axis of the ellipse makes
* with the horizontal axis. Thus, this equation is
* calculating the length of the hypotenuse of a triangle
* along that axis.
*/
double hypot = Math.sqrt(EB*EB + (EA-EC)*(EA-EC));
/* sqrt omitted, compare to squared limits below. */
double widthsquared = ((EA + EC + hypot)/2.0);
widthScale = Math.sqrt(widthsquared);
}
return (float) (lw / widthScale);
}
void strokeTo(Shape src,
AffineTransform at,
float width,

63
jdk/test/sun/pisces/ThinLineTest.java Normal file
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@ -0,0 +1,63 @@
/*
* Copyright 2009 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
import java.awt.*;
import java.awt.geom.Ellipse2D;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
/**
* @author chrisn@google.com (Chris Nokleberg)
* @author yamauchi@google.com (Hiroshi Yamauchi)
*/
public class ThinLineTest {
private static final int PIXEL = 381;
public static void main(String[] args) throws Exception {
BufferedImage image = new BufferedImage(200, 200, BufferedImage.TYPE_INT_RGB);
Graphics2D g = image.createGraphics();
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g.setPaint(Color.WHITE);
g.fill(new Rectangle(image.getWidth(), image.getHeight()));
g.scale(0.5 / PIXEL, 0.5 / PIXEL);
g.setPaint(Color.BLACK);
g.setStroke(new BasicStroke(PIXEL));
g.draw(new Ellipse2D.Double(PIXEL * 50, PIXEL * 50, PIXEL * 300, PIXEL * 300));
// To visually check it
//ImageIO.write(image, "PNG", new File(args[0]));
boolean nonWhitePixelFound = false;
for (int x = 0; x < 200; ++x) {
if (image.getRGB(x, 100) != Color.WHITE.getRGB()) {
nonWhitePixelFound = true;
break;
}
}
if (!nonWhitePixelFound) {
throw new RuntimeException("The thin line disappeared.");
}
}
}