PDFBOX-6077: Add regression tests for stencil-mask pattern fills

pdfbox/pom.xml

@@ -994,6 +994,45 @@
                             <sha512>2ee83beb6658792c6b963010462515ff1187aafe64930c1a7465dc26e86ab5236dc98cb006986e5fcd60876bedef7f00e4e1cb86bbf590bba000a00187af0ee3</sha512>
                         </configuration>
                     </execution>
+                    <execution>
+                        <id>PDFBOX-6077-1</id>
+                        <phase>generate-test-resources</phase>
+                        <goals>
+                            <goal>wget</goal>
+                        </goals>
+                        <configuration>
+                            <url>https://issues.apache.org/jira/secure/attachment/13078553/example.pdf</url>
+                            <outputDirectory>${project.build.directory}/pdfs</outputDirectory>
+                            <outputFileName>PDFBOX-6077-example.pdf</outputFileName>
+                            <sha512>f4faaa68062073ffdfd48119563f1e1a6eff6d9a063188dc2ec59ccc747277fcaa6139936cebf2f3f7b1b99b80ca13934fb4568658a169e0bf25bf4e748de101</sha512>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>PDFBOX-6077-2</id>
+                        <phase>generate-test-resources</phase>
+                        <goals>
+                            <goal>wget</goal>
+                        </goals>
+                        <configuration>
+                            <url>https://issues.apache.org/jira/secure/attachment/13078557/PDFBOX-5842-reduced.pdf</url>
+                            <outputDirectory>${project.build.directory}/pdfs</outputDirectory>
+                            <outputFileName>PDFBOX-5842-reduced.pdf</outputFileName>
+                            <sha512>c66b13230d343d6b0a2de81680f5d1ae7f8d92713acbc453ff36fe085831fa89127e0428d297e7494b87fc932ca8a721744db1fe79a41cc5c3cf7d631fc209fc</sha512>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>PDFBOX-5403</id>
+                        <phase>generate-test-resources</phase>
+                        <goals>
+                            <goal>wget</goal>
+                        </goals>
+                        <configuration>
+                            <url>https://issues.apache.org/jira/secure/attachment/13041734/bad+rendering.pdf</url>
+                            <outputDirectory>${project.build.directory}/pdfs</outputDirectory>
+                            <outputFileName>PDFBOX-5403-bad-rendering.pdf</outputFileName>
+                            <sha512>0d7160a4af04bf2f785bf4155f69876da4b7ff7a196e7eda1eb904c02c35aa03c31041d9339fda90322cb58bde16b87bae8460c617bfe5b8dc0670ddab102f62</sha512>
+                        </configuration>
+                    </execution>
                 </executions>
             </plugin>
         </plugins>

pdfbox/src/test/java/org/apache/pdfbox/rendering/TestQuality.java

@@ -56,4 +56,74 @@ void testPDFBox4831() throws IOException
             ValidateXImage.checkIdent(extractedImage, renderedImage);
         }
     }
+
+    /**
+     * PDFBOX-6077: a stencil mask filled with a pattern must not paint the gaps between the
+     * pattern's own tiles as opaque black. Before the fix, the stencil mask's alpha overwrote
+     * the pattern paint's own alpha instead of being combined with it, so any pixel the pattern
+     * didn't itself draw into turned solid black instead of staying transparent.
+     *
+     * @throws IOException
+     */
+    @Test
+    void testPDFBox6077() throws IOException
+    {
+        File file = new File(TARGET_PDF_DIR, "PDFBOX-6077-example.pdf");
+        try (PDDocument doc = Loader.loadPDF(file))
+        {
+            PDFRenderer renderer = new PDFRenderer(doc);
+            BufferedImage renderedImage = renderer.renderImageWithDPI(0, 100);
+            // a gap between the tiling pattern's own painted tiles, which must stay transparent
+            // (i.e. show the white page background) instead of turning opaque black
+            Assertions.assertEquals(0xFFFFFFFF, renderedImage.getRGB(280, 23));
+        }
+    }
+
+    /**
+     * PDFBOX-6077: a soft mask applied to a pattern that is used as a stencil mask fill must
+     * still be visible. Such a pattern is rendered into a separate scratch image rather than
+     * directly onto the page, and the soft mask's own alpha lookup is keyed to absolute
+     * page-device pixel coordinates, so a naive implementation renders it as fully transparent.
+     *
+     * @throws IOException
+     */
+    @Test
+    void testPDFBox5842() throws IOException
+    {
+        File file = new File(TARGET_PDF_DIR, "PDFBOX-5842-reduced.pdf");
+        try (PDDocument doc = Loader.loadPDF(file))
+        {
+            PDFRenderer renderer = new PDFRenderer(doc);
+            BufferedImage renderedImage = renderer.renderImageWithDPI(0, 100);
+            // a pixel within the soft-masked pattern's map marker icon; if the soft mask's alpha
+            // lookup is broken, this whole region renders as blank white instead
+            Assertions.assertNotEquals(0xFFFFFFFF, renderedImage.getRGB(267, 1329));
+        }
+    }
+
+    /**
+     * PDFBOX-5403: a stencil mask filled with a pattern repeated many times over a large area
+     * (e.g. one tiling-pattern-filled image per line of text) must not show a hairline seam
+     * between the pattern's own tiles as a visible gap. Combining the mask's alpha with the
+     * pattern's own alpha (see testPDFBox6077) can expose such a seam as a light gray line
+     * cutting through otherwise-solid text, if it isn't first smoothed over.
+     *
+     * @throws IOException
+     */
+    @Test
+    void testPDFBox5403() throws IOException
+    {
+        File file = new File(TARGET_PDF_DIR, "PDFBOX-5403-bad-rendering.pdf");
+        try (PDDocument doc = Loader.loadPDF(file))
+        {
+            PDFRenderer renderer = new PDFRenderer(doc);
+            BufferedImage renderedImage = renderer.renderImageWithDPI(2, 100);
+            // a pixel within a line of text rendered via a pattern-filled stencil mask; a
+            // hairline tile-boundary seam previously showed through as a washed-out gray streak
+            int rgb = renderedImage.getRGB(159, 115);
+            int red = (rgb >> 16) & 0xFF;
+            Assertions.assertTrue(red < 100,
+                    "expected a dark text pixel but was too light: " + Integer.toHexString(rgb));
+        }
+    }
 }