8064833: [macosx] Native font lookup uses family+style, not full name/postscript name
authorprr
Sun, 25 Jan 2015 15:53:46 -0800
changeset 28996 4d9228fac01a
parent 28995 097f07e8324e
child 28997 66d8297e3009
8064833: [macosx] Native font lookup uses family+style, not full name/postscript name Reviewed-by: bae, serb
jdk/src/java.desktop/macosx/classes/sun/font/CFont.java
jdk/src/java.desktop/macosx/classes/sun/font/CFontManager.java
jdk/src/java.desktop/macosx/native/libawt_lwawt/font/AWTFont.m
jdk/src/java.desktop/share/classes/sun/font/Font2D.java
jdk/src/java.desktop/share/classes/sun/font/FontFamily.java
jdk/src/java.desktop/share/classes/sun/font/TrueTypeFont.java
jdk/test/java/awt/FontClass/HelvLtOblTest.java
--- a/jdk/src/java.desktop/macosx/classes/sun/font/CFont.java	Fri Jan 23 13:47:46 2015 +0300
+++ b/jdk/src/java.desktop/macosx/classes/sun/font/CFont.java	Sun Jan 25 15:53:46 2015 -0800
@@ -77,14 +77,72 @@
     }
 
     private static native long createNativeFont(final String nativeFontName,
-                                                final int style,
-                                                final boolean isFakeItalic);
+                                                final int style);
     private static native void disposeNativeFont(final long nativeFontPtr);
 
     private boolean isFakeItalic;
     private String nativeFontName;
     private long nativeFontPtr;
 
+    private native float getWidthNative(final long nativeFontPtr);
+    private native float getWeightNative(final long nativeFontPtr);
+
+    private int fontWidth = -1;
+    private int fontWeight = -1;
+
+    @Override
+    public int getWidth() {
+        if (fontWidth == -1) {
+            // Apple use a range of -1 -> +1, where 0.0 is normal
+            // OpenType uses a % range from 50% -> 200% where 100% is normal
+            // and maps these onto the integer values 1->9.
+            // Since that is what Font2D.getWidth() expects, remap to that.
+            float fw = getWidthNative(getNativeFontPtr());
+            if (fw == 0.0) { // short cut the common case
+                fontWidth = Font2D.FWIDTH_NORMAL;
+                return fontWidth;
+            }
+            fw += 1.0; fw *= 100.0;
+            if (fw <= 50.0) {
+                fontWidth = 1;
+            } else if (fw <= 62.5) {
+                fontWidth = 2;
+            } else if (fw <= 75.0) {
+                fontWidth = 3;
+            } else if (fw <= 87.5) {
+                fontWidth = 4;
+            } else if (fw <= 100.0) {
+                fontWidth = 5;
+            } else if (fw <= 112.5) {
+                fontWidth = 6;
+            } else if (fw <= 125.0) {
+                fontWidth = 7;
+            } else if (fw <= 150.0) {
+                fontWidth = 8;
+            } else {
+                fontWidth = 9;
+            }
+        }
+        return fontWidth;
+   }
+
+    @Override
+    public int getWeight() {
+        if (fontWeight == -1) {
+            // Apple use a range of -1 -> +1, where 0 is medium/regular
+            // Map this on to the OpenType range of 100->900 where
+            // 500 is medium/regular.
+            // We'll actually map to 0->1000 but that's close enough.
+            float fw = getWeightNative(getNativeFontPtr());
+            if (fw == 0) {
+               return Font2D.FWEIGHT_NORMAL;
+            }
+            fw += 1.0; fw *= 500;
+            fontWeight = (int)fw;
+          }
+          return fontWeight;
+    }
+
     // this constructor is called from CFontWrapper.m
     public CFont(String name) {
         this(name, name);
@@ -94,10 +152,11 @@
         handle = new Font2DHandle(this);
         fullName = name;
         familyName = inFamilyName;
-        nativeFontName = inFamilyName;
+        nativeFontName = fullName;
         setStyle();
     }
 
+    /* Called from CFontManager too */
     public CFont(CFont other, String logicalFamilyName) {
         handle = new Font2DHandle(this);
         fullName = logicalFamilyName;
@@ -109,6 +168,7 @@
 
     public CFont createItalicVariant() {
         CFont font = new CFont(this, familyName);
+        font.nativeFontName = fullName;
         font.fullName =
             fullName + (style == Font.BOLD ? "" : "-") + "Italic-Derived";
         font.style |= Font.ITALIC;
@@ -118,7 +178,7 @@
 
     protected synchronized long getNativeFontPtr() {
         if (nativeFontPtr == 0L) {
-            nativeFontPtr = createNativeFont(nativeFontName, style, isFakeItalic);
+            nativeFontPtr = createNativeFont(nativeFontName, style);
 }
         return nativeFontPtr;
     }
--- a/jdk/src/java.desktop/macosx/classes/sun/font/CFontManager.java	Fri Jan 23 13:47:46 2015 +0300
+++ b/jdk/src/java.desktop/macosx/classes/sun/font/CFontManager.java	Sun Jan 25 15:53:46 2015 -0800
@@ -252,13 +252,42 @@
         final CFont font = new CFont(fontName, fontFamilyName);
 
         registerGenericFont(font);
+    }
 
-        if ((font.getStyle() & Font.ITALIC) == 0) {
-            registerGenericFont(font.createItalicVariant(), true);
+    void registerItalicDerived() {
+        FontFamily[] famArr = FontFamily.getAllFontFamilies();
+        for (int i=0; i<famArr.length; i++) {
+            FontFamily family = famArr[i];
+
+            Font2D f2dPlain = family.getFont(Font.PLAIN);
+            if (f2dPlain != null && !(f2dPlain instanceof CFont)) continue;
+            Font2D f2dBold = family.getFont(Font.BOLD);
+            if (f2dBold != null && !(f2dBold instanceof CFont)) continue;
+            Font2D f2dItalic = family.getFont(Font.ITALIC);
+            if (f2dItalic != null && !(f2dItalic instanceof CFont)) continue;
+            Font2D f2dBoldItalic = family.getFont(Font.BOLD|Font.ITALIC);
+            if (f2dBoldItalic != null && !(f2dBoldItalic instanceof CFont)) continue;
+
+            CFont plain = (CFont)f2dPlain;
+            CFont bold = (CFont)f2dBold;
+            CFont italic = (CFont)f2dItalic;
+            CFont boldItalic = (CFont)f2dBoldItalic;
+
+            if (bold == null) bold = plain;
+            if (plain == null && bold == null) continue;
+            if (italic != null && boldItalic != null) continue;
+            if (plain != null && italic == null) {
+               registerGenericFont(plain.createItalicVariant(), true);
+            }
+            if (bold != null && boldItalic == null) {
+               registerGenericFont(bold.createItalicVariant(), true);
+            }
         }
     }
 
     Object waitForFontsToBeLoaded  = new Object();
+    private boolean loadedAllFonts = false;
+
     public void loadFonts()
     {
         synchronized(waitForFontsToBeLoaded)
@@ -267,7 +296,11 @@
             java.security.AccessController.doPrivileged(
                 new java.security.PrivilegedAction<Object>() {
                     public Object run() {
-                        loadNativeFonts();
+                        if (!loadedAllFonts) {
+                           loadNativeFonts();
+                           registerItalicDerived();
+                           loadedAllFonts = true;
+                        }
                         return null;
                     }
                 }
--- a/jdk/src/java.desktop/macosx/native/libawt_lwawt/font/AWTFont.m	Fri Jan 23 13:47:46 2015 +0300
+++ b/jdk/src/java.desktop/macosx/native/libawt_lwawt/font/AWTFont.m	Sun Jan 25 15:53:46 2015 -0800
@@ -35,15 +35,11 @@
 #import "AWTStrike.h"
 #import "CoreTextSupport.h"
 
-
-#define DEBUG
-
 @implementation AWTFont
 
-- (id) initWithFont:(NSFont *)font isFakeItalic:(BOOL)isFakeItalic {
+- (id) initWithFont:(NSFont *)font {
     self = [super init];
     if (self) {
-        fIsFakeItalic = isFakeItalic;
         fFont = [font retain];
         fNativeCGFont = CTFontCopyGraphicsFont((CTFontRef)font, NULL);
     }
@@ -72,7 +68,6 @@
 
 + (AWTFont *) awtFontForName:(NSString *)name
                        style:(int)style
-                isFakeItalic:(BOOL)isFakeItalic
 {
     // create font with family & size
     NSFont *nsFont = [NSFont fontWithName:name size:1.0];
@@ -95,7 +90,7 @@
         nsFont = [[NSFontManager sharedFontManager] convertFont:nsFont toHaveTrait:NSBoldFontMask];
     }
 
-    return [[[AWTFont alloc] initWithFont:nsFont isFakeItalic:isFakeItalic] autorelease];
+    return [[[AWTFont alloc] initWithFont:nsFont] autorelease];
 }
 
 + (NSFont *) nsFontForJavaFont:(jobject)javaFont env:(JNIEnv *)env {
@@ -354,7 +349,7 @@
 JNIEXPORT jlong JNICALL
 Java_sun_font_CFont_createNativeFont
     (JNIEnv *env, jclass clazz,
-     jstring nativeFontName, jint style, jboolean isFakeItalic)
+     jstring nativeFontName, jint style)
 {
     AWTFont *awtFont = nil;
 
@@ -362,8 +357,7 @@
 
     awtFont =
         [AWTFont awtFontForName:JNFJavaToNSString(env, nativeFontName)
-         style:style
-         isFakeItalic:isFakeItalic]; // autoreleased
+         style:style]; // autoreleased
 
     if (awtFont) {
         CFRetain(awtFont); // GC
@@ -376,6 +370,52 @@
 
 /*
  * Class:     sun_font_CFont
+ * Method:    getWidthNative
+ * Signature: (J)F
+ */
+JNIEXPORT jfloat JNICALL
+Java_sun_font_CFont_getWidthNative
+    (JNIEnv *env, jobject cfont, jlong awtFontPtr)
+{
+    float widthVal;
+JNF_COCOA_ENTER(env);
+
+    AWTFont *awtFont = (AWTFont *)jlong_to_ptr(awtFontPtr);
+    NSFont* nsFont = awtFont->fFont;
+    NSFontDescriptor *fontDescriptor = nsFont.fontDescriptor;
+    NSDictionary *fontTraits = [fontDescriptor objectForKey : NSFontTraitsAttribute];
+    NSNumber *width = [fontTraits objectForKey : NSFontWidthTrait];
+    widthVal = (float)[width floatValue];
+
+JNF_COCOA_EXIT(env);
+   return (jfloat)widthVal;
+}
+
+/*
+ * Class:     sun_font_CFont
+ * Method:    getWeightNative
+ * Signature: (J)F
+ */
+JNIEXPORT jfloat JNICALL
+Java_sun_font_CFont_getWeightNative
+    (JNIEnv *env, jobject cfont, jlong awtFontPtr)
+{
+    float weightVal;
+JNF_COCOA_ENTER(env);
+
+    AWTFont *awtFont = (AWTFont *)jlong_to_ptr(awtFontPtr);
+    NSFont* nsFont = awtFont->fFont;
+    NSFontDescriptor *fontDescriptor = nsFont.fontDescriptor;
+    NSDictionary *fontTraits = [fontDescriptor objectForKey : NSFontTraitsAttribute];
+    NSNumber *weight = [fontTraits objectForKey : NSFontWeightTrait];
+    weightVal = (float)[weight floatValue];
+
+JNF_COCOA_EXIT(env);
+   return (jfloat)weightVal;
+}
+
+/*
+ * Class:     sun_font_CFont
  * Method:    disposeNativeFont
  * Signature: (J)V
  */
--- a/jdk/src/java.desktop/share/classes/sun/font/Font2D.java	Fri Jan 23 13:47:46 2015 +0300
+++ b/jdk/src/java.desktop/share/classes/sun/font/Font2D.java	Sun Jan 25 15:53:46 2015 -0800
@@ -157,6 +157,21 @@
         }
     }
 
+    public static final int FWIDTH_NORMAL = 5;    // OS/2 usWidthClass
+    public static final int FWEIGHT_NORMAL = 400; // OS/2 usWeightClass
+    public static final int FWEIGHT_BOLD   = 700; // OS/2 usWeightClass
+
+    public int getWidth() {
+        return FWIDTH_NORMAL;
+    }
+
+    public int getWeight() {
+        if ((style & Font.BOLD) !=0) {
+            return FWEIGHT_BOLD;
+        } else {
+            return FWEIGHT_NORMAL;
+        }
+    }
 
     int getRank() {
         return fontRank;
--- a/jdk/src/java.desktop/share/classes/sun/font/FontFamily.java	Fri Jan 23 13:47:46 2015 +0300
+++ b/jdk/src/java.desktop/share/classes/sun/font/FontFamily.java	Sun Jan 25 15:53:46 2015 -0800
@@ -27,6 +27,7 @@
 
 import java.io.File;
 import java.awt.Font;
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.Locale;
@@ -134,7 +135,98 @@
         return java.util.Objects.equals(newDir, existDir);
     }
 
+    /*
+     * We want a family to be of the same width and prefer medium/normal width.
+     * Once we find a particular width we accept more of the same width
+     * until we find one closer to normal when we 'evict' all existing fonts.
+     * So once we see a 'normal' width font we evict all members that are not
+     * normal width and then accept only new ones that are normal width.
+     *
+     * Once a font passes the width test we subject it to the weight test.
+     * For Plain we target the weight the closest that is <= NORMAL (400)
+     * For Bold we target the weight that is closest to BOLD (700).
+     *
+     * In the future, rather than discarding these fonts, we should
+     * extend the family to include these so lookups on these properties
+     * can locate them, as presently they will only be located by full name
+     * based lookup.
+     */
+
+    private int familyWidth = 0;
+    private boolean preferredWidth(Font2D font) {
+
+        int newWidth = font.getWidth();
+
+        if (familyWidth == 0) {
+            familyWidth = newWidth;
+            return true;
+        }
+
+        if (newWidth == familyWidth) {
+            return true;
+        }
+
+        if (Math.abs(Font2D.FWIDTH_NORMAL - newWidth) <
+            Math.abs(Font2D.FWIDTH_NORMAL - familyWidth))
+        {
+           if (FontUtilities.debugFonts()) {
+               FontUtilities.getLogger().info(
+               "Found more preferred width. New width = " + newWidth +
+               " Old width = " + familyWidth + " in font " + font +
+               " nulling out fonts plain: " + plain + " bold: " + bold +
+               " italic: " + italic + " bolditalic: " + bolditalic);
+           }
+           familyWidth = newWidth;
+           plain = bold = italic = bolditalic = null;
+           return true;
+        } else if (FontUtilities.debugFonts()) {
+               FontUtilities.getLogger().info(
+               "Family rejecting font " + font +
+               " of less preferred width " + newWidth);
+        }
+        return false;
+    }
+
+    private boolean closerWeight(Font2D currFont, Font2D font, int style) {
+        if (familyWidth != font.getWidth()) {
+            return false;
+        }
+
+        if (currFont == null) {
+            return true;
+        }
+
+        if (FontUtilities.debugFonts()) {
+            FontUtilities.getLogger().info(
+            "New weight for style " + style + ". Curr.font=" + currFont +
+            " New font="+font+" Curr.weight="+ + currFont.getWeight()+
+            " New weight="+font.getWeight());
+        }
+
+        int newWeight = font.getWeight();
+        switch (style) {
+            case Font.PLAIN:
+            case Font.ITALIC:
+                return (newWeight <= Font2D.FWEIGHT_NORMAL &&
+                        newWeight > currFont.getWeight());
+
+            case Font.BOLD:
+            case Font.BOLD|Font.ITALIC:
+                return (Math.abs(newWeight - Font2D.FWEIGHT_BOLD) <
+                        Math.abs(currFont.getWeight() - Font2D.FWEIGHT_BOLD));
+
+            default:
+               return false;
+        }
+    }
+
     public void setFont(Font2D font, int style) {
+
+        if (FontUtilities.isLogging()) {
+            FontUtilities.getLogger().info(
+            "Request to add " + font + " with style " + style +
+            " to family " + this);
+        }
         /* Allow a lower-rank font only if its a file font
          * from the exact same source as any previous font.
          */
@@ -152,19 +244,27 @@
         switch (style) {
 
         case Font.PLAIN:
-            plain = font;
+            if (preferredWidth(font) && closerWeight(plain, font, style)) {
+                plain = font;
+            }
             break;
 
         case Font.BOLD:
-            bold = font;
+            if (preferredWidth(font) && closerWeight(bold, font, style)) {
+                bold = font;
+            }
             break;
 
         case Font.ITALIC:
-            italic = font;
+            if (preferredWidth(font) && closerWeight(italic, font, style)) {
+                italic = font;
+            }
             break;
 
         case Font.BOLD|Font.ITALIC:
-            bolditalic = font;
+            if (preferredWidth(font) && closerWeight(bolditalic, font, style)) {
+                bolditalic = font;
+            }
             break;
 
         default:
@@ -316,6 +416,11 @@
         return allLocaleNames.get(name.toLowerCase());
     }
 
+    public static FontFamily[] getAllFontFamilies() {
+       Collection<FontFamily> families = familyNameMap.values();
+       return families.toArray(new FontFamily[0]);
+    }
+
     public String toString() {
         return
             "Font family: " + familyName +
--- a/jdk/src/java.desktop/share/classes/sun/font/TrueTypeFont.java	Fri Jan 23 13:47:46 2015 +0300
+++ b/jdk/src/java.desktop/share/classes/sun/font/TrueTypeFont.java	Sun Jan 25 15:53:46 2015 -0800
@@ -963,6 +963,18 @@
         setStyle(getTableBuffer(os_2Tag));
     }
 
+    private int fontWidth = 0;
+    @Override
+    public int getWidth() {
+       return (fontWidth > 0) ? fontWidth : super.getWidth();
+    }
+
+    private int fontWeight = 0;
+    @Override
+    public int getWeight() {
+       return (fontWeight > 0) ? fontWeight : super.getWeight();
+    }
+
     /* TrueTypeFont can use the fsSelection fields of OS/2 table
      * to determine the style. In the unlikely case that doesn't exist,
      * can use macStyle in the 'head' table but simpler to
@@ -978,8 +990,15 @@
     private static final int fsSelectionBoldBit    = 0x00020;
     private static final int fsSelectionRegularBit = 0x00040;
     private void setStyle(ByteBuffer os_2Table) {
+        if (os_2Table == null) {
+            return;
+        }
+        if (os_2Table.capacity() >= 8) {
+            fontWeight = os_2Table.getChar(4) & 0xffff;
+            fontWidth  = os_2Table.getChar(6) & 0xffff;
+        }
         /* fsSelection is unsigned short at buffer offset 62 */
-        if (os_2Table == null || os_2Table.capacity() < 64) {
+        if (os_2Table.capacity() < 64) {
             super.setStyle();
             return;
         }
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/java/awt/FontClass/HelvLtOblTest.java	Sun Jan 25 15:53:46 2015 -0800
@@ -0,0 +1,166 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8064833
+ * @summary Test correct font is obtained via famil+style
+ * @run main HelvLtOblTest
+ */
+
+import javax.swing.JComponent;
+import javax.swing.JFrame;
+import javax.swing.SwingUtilities;
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.Font;
+import java.awt.Graphics;
+import java.awt.Graphics2D;
+import java.awt.GraphicsEnvironment;
+import java.awt.RenderingHints;
+import java.awt.font.FontRenderContext;
+import java.awt.font.GlyphVector;
+import java.awt.image.BufferedImage;
+
+public class HelvLtOblTest extends JComponent {
+
+    static Font helvFont = null;
+
+    static int[] codes = { 0x23, 0x4a, 0x48, 0x3, 0x4a, 0x55, 0x42, 0x4d,
+                    0x4a, 0x44, 0x3,
+                    0x53, 0x46, 0x45, 0x3, 0x55, 0x46, 0x59, 0x55, };
+
+    static String str = "Big italic red text";
+
+    public static void main(String[] args) throws Exception {
+        String os = System.getProperty("os.name");
+        if (!os.startsWith("Mac")) {
+             return;
+        }
+        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
+        Font[] fonts = ge.getAllFonts();
+        for (int i=0; i<fonts.length; i++) {
+            if (fonts[i].getPSName().equals("Helvetica-LightOblique")) {
+                 helvFont = fonts[i];
+                 break;
+            }
+        }
+        if (helvFont == null) {
+            return;
+        }
+        final HelvLtOblTest test = new HelvLtOblTest();
+        SwingUtilities.invokeLater(() -> {
+            JFrame f = new JFrame();
+            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+            f.add("Center", test);
+            f.pack();
+            f.setVisible(true);
+        });
+        test.compareImages();
+    }
+
+    public Dimension getPreferredSize() {
+      return new Dimension(400,400);
+    }
+
+    public void paintComponent(Graphics g) {
+         super.paintComponent(g);
+         Graphics2D g2 = (Graphics2D)g;
+         FontRenderContext frc = new FontRenderContext(null, true, true);
+         Font f = helvFont.deriveFont(Font.PLAIN, 40);
+         System.out.println("font = " +f.getFontName());
+         GlyphVector gv = f.createGlyphVector(frc, codes);
+         g.setFont(f);
+         g.setColor(Color.white);
+         g.fillRect(0,0,400,400);
+         g.setColor(Color.black);
+         g2.drawGlyphVector(gv, 5,200);
+         g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
+                             RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
+         g2.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS,
+                             RenderingHints.VALUE_FRACTIONALMETRICS_ON);
+         g2.drawString(str, 5, 250);
+    }
+
+    void compareImages() {
+         BufferedImage bi0 = drawText(false);
+         BufferedImage bi1 = drawText(true);
+         compare(bi0, bi1);
+    }
+
+    BufferedImage drawText(boolean doGV) {
+        int w = 400;
+        int h = 50;
+        BufferedImage bi = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
+        Graphics2D g = bi.createGraphics();
+        g.setColor(Color.white);
+        g.fillRect(0,0,w,h);
+        g.setColor(Color.black);
+        Font f = helvFont.deriveFont(Font.PLAIN, 40);
+        g.setFont(f);
+        int x = 5;
+        int y = h - 10;
+        if (doGV) {
+            FontRenderContext frc = new FontRenderContext(null, true, true);
+            GlyphVector gv = f.createGlyphVector(frc, codes);
+            g.drawGlyphVector(gv, 5, y);
+       } else {
+           g.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
+                              RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
+           g.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS,
+                              RenderingHints.VALUE_FRACTIONALMETRICS_ON);
+           g.drawString(str, x, y);
+       }
+       return bi;
+    }
+
+    // Need to allow for minimal rounding error, so allow each component
+    // to differ by 1.
+    void compare(BufferedImage bi0, BufferedImage bi1) {
+        int wid = bi0.getWidth();
+        int hgt = bi0.getHeight();
+        for (int x=0; x<wid; x++) {
+            for (int y=0; y<hgt; y++) {
+                int rgb0 = bi0.getRGB(x, y);
+                int rgb1 = bi1.getRGB(x, y);
+                if (rgb0 == rgb1) continue;
+                int r0 = (rgb0 & 0xff0000) >> 16;
+                int r1 = (rgb1 & 0xff0000) >> 16;
+                int rdiff = r0-r1; if (rdiff<0) rdiff = -rdiff;
+                int g0 = (rgb0 & 0x00ff00) >> 8;
+                int g1 = (rgb1 & 0x00ff00) >> 8;
+                int gdiff = g0-g1; if (gdiff<0) gdiff = -gdiff;
+                int b0 = (rgb0 & 0x0000ff);
+                int b1 = (rgb1 & 0x0000ff);
+                int bdiff = b0-b1; if (bdiff<0) bdiff = -bdiff;
+                if (rdiff > 1 || gdiff > 1 || bdiff > 1) {
+                    throw new RuntimeException(
+                      "Images differ at x=" + x + " y="+ y + " " +
+                      Integer.toHexString(rgb0) + " vs " +
+                      Integer.toHexString(rgb1));
+                }
+            }
+        }
+    }
+
+}