PDFBOX-4073 Choosable Coordinate-Unitsystem

pdfbox/src/main/java/org/apache/pdfbox/pdmodel/PDAbstractContentStream.java

@@ -1674,4 +1674,31 @@ private List<Integer> applyGSUBRules(GsubWorker gsubWorker, ByteArrayOutputStrea
         return glyphIdsAfterGsub;
 
     }
+
+    /**
+     * Does a length unit conversion from millimeters or inches (depending on user choice) to points.
+     *
+     * @param items Items that needs to be converted.
+     * @param unit_type Specifies desired length unit (mm or inch) for conversion.
+     * @throws IllegalArgumentException If desired length unit is not supported.
+     */
+    public static final void convertUnit(List<Float> items, String unitType)
+    {
+        float multiplier = 1;
+        switch (unitType) {
+            case "mm":
+                multiplier = 1 / (10 * 2.54f) * 72;
+                break;
+            case "inch":
+                multiplier = 72;
+                break;
+            default:
+                throw new IllegalArgumentException(
+                        "could not find the unit type: " + unitType);
+        }
+
+        for (int i=0; i < items.size(); i++) {
+            items.set(i, items.get(i) * multiplier);
+        }
+    }
 }

pdfbox/src/test/java/org/apache/pdfbox/pdmodel/TestPDPageContentStream.java

@@ -17,8 +17,10 @@
 package org.apache.pdfbox.pdmodel;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.List;
 import org.apache.pdfbox.contentstream.operator.Operator;
 import org.apache.pdfbox.contentstream.operator.OperatorName;
@@ -167,4 +169,29 @@ void testCloseContract() throws IOException
             contentStream.close();
         }
     }
+
+     /**
+     * PDFBOX-4073: test implemented choosable coordinate-unitsystem
+     * Checks that unitconversion is done right. 
+     * Arguably the test could be also in some other file
+     */
+    @Test 
+     void testUnitConversion() 
+     {
+        List<Float> itemsMm = Arrays.asList(1.0f, 2.4f);
+        List<Float> itemsInch = Arrays.asList(1.0f, 2.4f);
+        List<Float> itemsInMm = Arrays.asList(1.0f /(10 * 2.54f) * 72, 2.4f /(10 * 2.54f) * 72);
+        List<Float> itemsInInch = Arrays.asList(1.0f * 72, 2.4f * 72);
+
+        PDAbstractContentStream.convertUnit(itemsMm, "mm");
+        PDAbstractContentStream.convertUnit(itemsInch, "inch");
+        // Should be converted to millimeters
+        assertEquals(itemsInMm, itemsMm);
+        // Should be converted to inches
+        assertEquals(itemsInInch, itemsInch);
+        // Should throw IllegalArgumentException if the unit is not valid
+        assertThrows(IllegalArgumentException.class, () -> {
+            PDAbstractContentStream.convertUnit(itemsMm, "invalid_unit");
+        });   
+    }
 }