Use signed arithmetic when reading rectangle (#1131)

* Use signed arithmetic when reading rectangle

An operation such as DirectBitsRect can fail if the origin is -ve and we're applying a screen image ratio. See for example P564B1400.pict

* Fix copy/paste error in testNegativeOrigin()

---------

Co-authored-by: Harald Kuhr <harald.kuhr@gmail.com>

imageio/imageio-pict/src/main/java/com/twelvemonkeys/imageio/plugins/pict/PICTImageReader.java

@@ -2406,10 +2406,10 @@ public final class PICTImageReader extends ImageReaderBase {
      * @throws IOException if an I/O error occurs while reading the image.
      */
     private void readRectangle(DataInput pStream, Rectangle pDestRect) throws IOException {
-        int y = pStream.readUnsignedShort();
+        int y = pStream.readShort();
-        int x = pStream.readUnsignedShort();
+        int x = pStream.readShort();
-        int h = pStream.readUnsignedShort();
+        int h = pStream.readShort();
-        int w = pStream.readUnsignedShort();
+        int w = pStream.readShort();
 
         pDestRect.setLocation(getXPtCoord(x), getYPtCoord(y));
         pDestRect.setSize(getXPtCoord(w - x), getYPtCoord(h - y));

imageio/imageio-pict/src/test/java/com/twelvemonkeys/imageio/plugins/pict/PICTImageReaderTest.java

@@ -84,6 +84,7 @@ public class PICTImageReaderTest extends ImageReaderAbstractTest<PICTImageReader
                 new TestData(getClassLoaderResource("/pict/FC10.PCT"), new Dimension(2265, 2593)),
                 // 1000 DPI with bounding box not matching DPI
                 new TestData(getClassLoaderResource("/pict/oom.pict"), new Dimension(1713, 1263)),
+                new TestData(getClassLoaderResource("/pict/P564B1400.pict"), new Dimension(1745, 1022)),
                 new TestData(getClassLoaderResource("/pict/cow.pict"), new Dimension(787, 548)),
                 new TestData(getClassLoaderResource("/pict/CatDV==2.0=1=.pict"), new Dimension(375, 165)),
                 new TestData(getClassLoaderResource("/pict/Picture14.pict"), new Dimension(404, 136)),
@@ -252,6 +253,23 @@ public class PICTImageReaderTest extends ImageReaderAbstractTest<PICTImageReader
         reader.read(0);
     }
 
+    @Test
+    public void testNegativeOrigin() throws IOException {
+        PICTImageReader reader = createReader();
+
+        try (ImageInputStream stream = ImageIO.createImageInputStream(getClassLoaderResource("/pict/P564B1400.pict"))) {
+            reader.setInput(stream);
+            // This file has a DirectBitsRect opcode with a destination of (0,-1) which wraps to 65535 if we read
+            // it using unsigned arithmetic
+            BufferedImage image = reader.read(0, null);
+            assertRGBEquals("RGB values differ", 0xfffcfcfc, image.getRGB(10, 10), 1);    // was transparent 00ffffff
+            assertRGBEquals("RGB values differ", 0xffe6e6e6, image.getRGB(100, 500), 1);
+        }
+        finally {
+            reader.dispose();
+        }
+    }
+
     @Test
     public void testFrameBoundsIssue() throws IOException {
         PICTImageReader reader = createReader();