Implement line color filter

src/main/java/technology/tabula/CommandLineApp.java

@@ -44,13 +44,15 @@ public class CommandLineApp {
     private OutputFormat outputFormat;
     private String password;
     private TableExtractor tableExtractor;
+    private Integer lineColorFilter;
 
     public CommandLineApp(Appendable defaultOutput, CommandLine line) throws ParseException {
         this.defaultOutput = defaultOutput;
         this.pageAreas = CommandLineApp.whichAreas(line);
         this.pages = CommandLineApp.whichPages(line);
         this.outputFormat = CommandLineApp.whichOutputFormat(line);
         this.tableExtractor = CommandLineApp.createExtractor(line);
+        this.lineColorFilter = CommandLineApp.whichLineColorFilter(line);
 
         if (line.hasOption('s')) {
             this.password = line.getOptionValue('s');
@@ -195,7 +197,7 @@ private void extractFile(File pdfFile, Appendable outFile) throws ParseException
     }
 
     private PageIterator getPageIterator(PDDocument pdfDocument) throws IOException {
-        ObjectExtractor extractor = new ObjectExtractor(pdfDocument);
+        ObjectExtractor extractor = new ObjectExtractor(pdfDocument, lineColorFilter);
         return (pages == null) ?
                 extractor.extract() :
                 extractor.extract(pages);
@@ -260,6 +262,23 @@ private static ExtractionMethod whichExtractionMethod(CommandLine line) {
         return ExtractionMethod.DECIDE;
     }
 
+    private static Integer whichLineColorFilter(CommandLine line) throws ParseException {
+        if (!line.hasOption("line-color-filter")) {
+            return null;
+        }
+
+        Integer result;
+        try {
+            result = Integer.parseInt(line.getOptionValue("line-color-filter"), 16);
+        } catch (NumberFormatException e) {
+            throw new ParseException("line-color-filter parameter must be a hexadecimal number");
+        }
+        if (result < 0 || result > 0xFFFFFF) {
+            throw new ParseException("line-color-filter parameter must be at most FFFFFF");
+        }
+        return result;
+    }
+
     private static TableExtractor createExtractor(CommandLine line) throws ParseException {
         TableExtractor extractor = new TableExtractor();
         extractor.setGuess(line.hasOption('g'));
@@ -358,6 +377,12 @@ public static Options buildOptions() {
                 .hasArg()
                 .argName("PAGES")
                 .build());
+        o.addOption(Option.builder(null)
+                .longOpt("line-color-filter")
+                .desc("Only consider lines of this color to be lattice lines. Example: --line-color-filter DEADBE .")
+                .hasArg()
+                .argName("COLOR")
+                .build());
 
         return o;
     }

src/main/java/technology/tabula/ObjectExtractor.java

@@ -8,9 +8,15 @@
 public class ObjectExtractor implements java.io.Closeable {
 
     private final PDDocument pdfDocument;
+    private final Integer lineColorFilter;
 
     public ObjectExtractor(PDDocument pdfDocument) {
+        this(pdfDocument, null);
+    }
+
+    public ObjectExtractor(PDDocument pdfDocument, Integer lineColorFilter) {
         this.pdfDocument = pdfDocument;
+        this.lineColorFilter = lineColorFilter;
     }
 
     // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - //
@@ -20,7 +26,7 @@ protected Page extractPage(Integer pageNumber) throws IOException {
         }
         PDPage page = pdfDocument.getPage(pageNumber - 1);
 
-        ObjectExtractorStreamEngine streamEngine = new ObjectExtractorStreamEngine(page);
+        ObjectExtractorStreamEngine streamEngine = new ObjectExtractorStreamEngine(page, lineColorFilter);
         streamEngine.processPage(page);
 
         TextStripper textStripper = new TextStripper(pdfDocument, pageNumber);

src/main/java/technology/tabula/ObjectExtractorStreamEngine.java

@@ -7,6 +7,7 @@
 import java.awt.geom.PathIterator;
 import java.awt.geom.Point2D;
 import java.awt.geom.Rectangle2D;
+import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
@@ -15,14 +16,17 @@
 import org.apache.pdfbox.cos.COSName;
 import org.apache.pdfbox.pdmodel.PDPage;
 import org.apache.pdfbox.pdmodel.common.PDRectangle;
+import org.apache.pdfbox.pdmodel.graphics.color.PDColor;
 import org.apache.pdfbox.pdmodel.graphics.image.PDImage;
+import org.apache.pdfbox.pdmodel.graphics.state.PDGraphicsState;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import static java.awt.geom.PathIterator.*;
 
 class ObjectExtractorStreamEngine extends PDFGraphicsStreamEngine {
 
+    private Integer lineColorFilter;
     protected List<Ruling> rulings;
     private AffineTransform pageTransform;
     private boolean extractRulingLines = true;
@@ -32,8 +36,9 @@ class ObjectExtractorStreamEngine extends PDFGraphicsStreamEngine {
 
     private static final float RULING_MINIMUM_LENGTH = 0.01f;
 
-    protected ObjectExtractorStreamEngine(PDPage page) {
+    protected ObjectExtractorStreamEngine(PDPage page, Integer lineColorFilter) {
         super(page);
+        this.lineColorFilter = lineColorFilter;
         logger = LoggerFactory.getLogger(ObjectExtractorStreamEngine.class);
         rulings = new ArrayList<>();
 
@@ -130,16 +135,11 @@ public void strokePath()  {
     }
 
     private void strokeOrFillPath(boolean isFill) {
-        if (!extractRulingLines) {
+        if (!extractRulingLines || filterPathByColor(isFill) || filterPathBySegmentType()) {
             currentPath.reset();
             return;
         }
 
-        boolean didNotPassedTheFilter = filterPathBySegmentType();
-        if (didNotPassedTheFilter) return;
-
-        // TODO: how to implement color filter?
-
         // Skip the first path operation and save it as the starting point.
         PathIterator pathIterator = currentPath.getPathIterator(getPageTransform());
 
@@ -191,6 +191,32 @@ private void strokeOrFillPath(boolean isFill) {
         currentPath.reset();
     }
 
+    private boolean filterPathByColor (boolean isFill) {
+        if (lineColorFilter == null) {
+            return false;
+        }
+
+        try {
+            PDGraphicsState state = getGraphicsState();
+            PDColor currentColor;
+            if (isFill) {
+                currentColor = state.getNonStrokingColor();
+            } else {
+                currentColor = state.getStrokingColor();
+            }
+            return currentColor.toRGB() != lineColorFilter;
+        } catch (IOException e) {
+            System.err.println("Color conversion failed:");
+            e.printStackTrace();
+            return false;
+        } catch (IllegalStateException e) {
+            System.err.println("Cannot convert pattern color:");
+            e.printStackTrace();
+            return false;
+        }
+        // TODO: if the toRGB() method throws an exception, should the color be valid or not?
+    }
+
     private boolean filterPathBySegmentType() {
         PathIterator pathIterator = currentPath.getPathIterator(pageTransform);
         float[] coordinates = new float[6];

src/test/java/technology/tabula/TestObjectExtractor.java

@@ -83,6 +83,19 @@ public void testShouldDetectRulings() throws IOException {
         }
     }
 
+    @Test
+    public void testShouldFilterRulingsByColor() throws IOException {
+        PDDocument pdf_document = PDDocument.load(new File("src/test/resources/technology/tabula/should_filter_rulings_by_color.pdf"));
+        try (ObjectExtractor oe = new ObjectExtractor(pdf_document, 0)) {
+            PageIterator pi = oe.extract();
+
+            Page page = pi.next();
+            List<Ruling> rulings = page.getRulings();
+
+            assertEquals(7, rulings.size());
+        }
+    }
+
     @Test
     public void testDontThrowNPEInShfill() throws IOException {
         PDDocument pdf_document = PDDocument.load(new File("src/test/resources/technology/tabula/labor.pdf"));