Add sharpening filter to this implementation too

[zxing.git] / javame / src / com / google / zxing / client / j2me / LCDUIImageMonochromeBitmapSource.java

diff --git a/javame/src/com/google/zxing/client/j2me/LCDUIImageMonochromeBitmapSource.java b/javame/src/com/google/zxing/client/j2me/LCDUIImageMonochromeBitmapSource.java
index 2b7bd10..f123abb 100644 (file)
--- a/javame/src/com/google/zxing/client/j2me/LCDUIImageMonochromeBitmapSource.java
+++ b/javame/src/com/google/zxing/client/j2me/LCDUIImageMonochromeBitmapSource.java
@@ -16,8 +16,9 @@
 
 package com.google.zxing.client.j2me;
 
-import com.google.zxing.MonochromeBitmapSource;
 import com.google.zxing.BlackPointEstimationMethod;
+import com.google.zxing.MonochromeBitmapSource;
+import com.google.zxing.ReaderException;
 import com.google.zxing.common.BitArray;
 import com.google.zxing.common.BlackPointEstimator;
 
@@ -25,10 +26,10 @@ import javax.microedition.lcdui.Image;
 
 /**
  * <p>An implementation based on Java ME's {@link Image} representation.</p>
- * 
+ *
  * @author Sean Owen (srowen@google.com), Daniel Switkin (dswitkin@google.com)
  */
-final class LCDUIImageMonochromeBitmapSource implements MonochromeBitmapSource {
+public final class LCDUIImageMonochromeBitmapSource implements MonochromeBitmapSource {
 
   private final int[] rgbPixels;
   private final int width;
@@ -36,12 +37,12 @@ final class LCDUIImageMonochromeBitmapSource implements MonochromeBitmapSource {
   private int blackPoint;
   private BlackPointEstimationMethod lastMethod;
   private int lastArgument;
-  
+
   private static final int LUMINANCE_BITS = 5;
   private static final int LUMINANCE_SHIFT = 8 - LUMINANCE_BITS;
   private static final int LUMINANCE_BUCKETS = 1 << LUMINANCE_BITS;
 
-  LCDUIImageMonochromeBitmapSource(final Image image) {
+  public LCDUIImageMonochromeBitmapSource(Image image) {
     width = image.getWidth();
     height = image.getHeight();
     rgbPixels = new int[width * height];
@@ -56,14 +57,35 @@ final class LCDUIImageMonochromeBitmapSource implements MonochromeBitmapSource {
   }
 
   public BitArray getBlackRow(int y, BitArray row, int startX, int getWidth) {
-    if (row == null) {
+    if (row == null || row.getSize() < getWidth) {
       row = new BitArray(getWidth);
     } else {
       row.clear();
     }
-    for (int i = 0, offset = y * width + startX; i < getWidth; i++, offset++) {
-      if (computeRGBLuminance(rgbPixels[offset]) < blackPoint) {
-        row.set(i);
+
+    // If the current decoder calculated the blackPoint based on one row, assume we're trying to
+    // decode a 1D barcode, and apply some sharpening.
+    // TODO: We may want to add a fifth parameter to request the amount of shapening to be done.
+    if (lastMethod.equals(BlackPointEstimationMethod.ROW_SAMPLING)) {
+      int offset = y * width + startX;
+      int left = computeRGBLuminance(rgbPixels[offset]);
+      offset++;
+      int center = computeRGBLuminance(rgbPixels[offset]);
+      for (int i = 1; i < getWidth - 1; i++, offset++) {
+        int right = computeRGBLuminance(rgbPixels[offset + 1]);
+        // Simple -1 4 -1 box filter with a weight of 2
+        int luminance = ((center << 2) - left - right) >> 1;
+        if (luminance < blackPoint) {
+          row.set(i);
+        }
+        left = center;
+        center = right;
+      }
+    } else {
+      for (int i = 0, offset = y * width + startX; i < getWidth; i++, offset++) {
+        if (computeRGBLuminance(rgbPixels[offset]) < blackPoint) {
+          row.set(i);
+        }
       }
     }
     return row;
@@ -77,7 +99,7 @@ final class LCDUIImageMonochromeBitmapSource implements MonochromeBitmapSource {
     return width;
   }
 
-  public void estimateBlackPoint(BlackPointEstimationMethod method, int argument) {
+  public void estimateBlackPoint(BlackPointEstimationMethod method, int argument) throws ReaderException {
     if (!method.equals(lastMethod) || argument != lastArgument) {
       int[] histogram = new int[LUMINANCE_BUCKETS];
       if (method.equals(BlackPointEstimationMethod.TWO_D_SAMPLING)) {
@@ -106,20 +128,36 @@ final class LCDUIImageMonochromeBitmapSource implements MonochromeBitmapSource {
     return lastMethod;
   }
 
+  public MonochromeBitmapSource rotateCounterClockwise() {
+    throw new IllegalStateException("Rotate not supported");
+  }
+
+  public boolean isRotateSupported() {
+    return false;
+  }
+
   /**
-   * Extracts luminance from a pixel from this source. By default, the source is assumed to use RGB,
-   * so this implementation computes luminance is a function of a red, green and blue components as
-   * follows:
-   *
-   * <code>Y = 0.299R + 0.587G + 0.114B</code>
-   *
-   * where R, G, and B are values in [0,1].
+   * An optimized approximation of a more proper conversion from RGB to luminance which
+   * only uses shifts. See BufferedImageMonochromeBitmapSource for an original version.
    */
   private static int computeRGBLuminance(int pixel) {
-    // Coefficients add up to 1024 to make the divide into a fast shift
-    return (306 * ((pixel >> 16) & 0xFF) +
-        601 * ((pixel >> 8) & 0xFF) +
-        117 * (pixel & 0xFF)) >> 10;
+    // Instead of multiplying by 306, 601, 117, we multiply by 256, 512, 256, so that
+    // the multiplies can be implemented as shifts.
+    //
+    // Really, it's:
+    //
+    // return ((((pixel >> 16) & 0xFF) << 8) +
+    //         (((pixel >>  8) & 0xFF) << 9) +
+    //         (( pixel        & 0xFF) << 8)) >> 10;
+    //
+    // That is, we're replacing the coefficients in the original with powers of two,
+    // which can be implemented as shifts, even though changing the coefficients slightly
+    // corrupts the conversion. Not significant for our purposes.
+    //
+    // But we can get even cleverer and eliminate a few shifts:
+    return (((pixel & 0x00FF0000) >> 16)  +
+            ((pixel & 0x0000FF00) >>  7) +
+            ( pixel & 0x000000FF       )) >> 2;
   }
 
 }
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