Fixed a bug in monochrome BMP decoding and added a simple test.

pom.xml

@@ -14,12 +14,28 @@
 	<inceptionYear>2006</inceptionYear>
 
     <properties>
-        <maven.compiler.source>6</maven.compiler.source>
-        <maven.compiler.target>6</maven.compiler.target>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
     </properties>
 
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.12</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
     <build>
         <sourceDirectory>${basedir}/src</sourceDirectory>
+        <testSourceDirectory>${basedir}/test</testSourceDirectory>
+
+        <testResources>
+            <testResource>
+                <directory>${basedir}/test-resources</directory>
+            </testResource>
+        </testResources>
     </build>
 
 </project>

src/net/sf/image4j/codec/bmp/BMPDecoder.java

@@ -47,7 +47,7 @@ public BMPDecoder(java.io.InputStream in) throws IOException {
     //DataOffset [4] file offset to raster data
     int dataOffset = lis.readIntLE();
 
-    /* info header [40] */
+    /* info header */
 
     infoHeader = readInfoHeader(lis);
 
@@ -264,7 +264,7 @@ public static BufferedImage read1(InfoHeader infoHeader,
     int padBits = bitsPerLine - dataBitsPerLine;
     int padBytes = padBits / 8;
 
-    int bytesPerLine = (int) (bitsPerLine / 8);
+    int bytesPerLine = (infoHeader.iWidth + 31)/32 * 4;
     int[] line = new int[bytesPerLine];
 
     for (int y = infoHeader.iHeight - 1; y >= 0; y--) {

src/net/sf/image4j/codec/bmp/InfoHeader.java

@@ -99,11 +99,14 @@ public InfoHeader(net.sf.image4j.io.LittleEndianInputStream in, int infoSize) th
   protected void init(net.sf.image4j.io.LittleEndianInputStream in, int infoSize) throws IOException {
     this.iSize = infoSize;
 
+    // Only 40-byte header is read. If actual header is longer, just skip the rest
+    int ntHeaderSize = 40;
+
     //Width
     iWidth = in.readIntLE();
     //Height
     iHeight = in.readIntLE();
-    //Planes (=1)
+    //Planes 
     sPlanes = in.readShortLE();
     //Bit count
     sBitCount = in.readShortLE();
@@ -123,13 +126,18 @@ protected void init(net.sf.image4j.io.LittleEndianInputStream in, int infoSize)
     iColorsUsed = in.readIntLE();
     //Colors important - number of important colors 0 = all
     iColorsImportant = in.readIntLE();
+
+    if(iSize > ntHeaderSize){
+    	in.skipBytes(infoSize - ntHeaderSize);
+    }
+
   }
 
   /**
    * Creates an <tt>InfoHeader</tt> with default values.
    */
   public InfoHeader() {
-    //Size of InfoHeader structure = 40
+    //Size of InfoHeader structure = 40 for Windows NT BITMAPINFOHEADER, see Wikipedia
     iSize = 40;
     //Width
     iWidth = 0;

test/net/sf/image4j/codec/bmp/BMPDecoderTest.java

@@ -0,0 +1,57 @@
+package net.sf.image4j.codec.bmp;
+
+import static org.junit.Assert.*;
+
+import java.awt.image.BufferedImage;
+import java.awt.image.Raster;
+import java.io.InputStream;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.BlockJUnit4ClassRunner;
+
+@RunWith(BlockJUnit4ClassRunner.class)
+public class BMPDecoderTest {
+
+    InputStream is;
+
+    String filename = "/monochrome.bmp";
+
+    @Before
+    public void setUp() throws Exception {
+        is = getClass().getResourceAsStream(filename);
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        if (is != null) {
+            is.close();
+        }
+    }
+
+    @Test
+    public void testMonochromeImage() throws Exception {
+        assertNotNull("Test file missing",
+                getClass().getResource(filename));
+        BufferedImage image = BMPDecoder.read(is);
+
+        assertEquals("Wrong width", 4, image.getWidth());
+        assertEquals("Wrong height", 8, image.getHeight());
+        assertEquals("Wrong image type", BufferedImage.TYPE_BYTE_BINARY, image.getType());
+
+        Raster raster = image.getRaster();
+        assertEquals("Wrong number of bands", 1, raster.getNumBands());
+        for (int x = 0; x < image.getWidth(); ++x) {
+            for (int y = 0; y < image.getHeight(); ++y) {
+                if (x == y) {
+                    assertEquals("Wrong pixel on the main diagonal", 1, raster.getSample(x, y, 0));
+                } else {
+                    assertEquals("Wrong pixel outside the main diagonal", 0, raster.getSample(x, y, 0));
+                }
+            }
+        }
+    }
+
+}