package com.google.zxing.client.j2me;
+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;
import javax.microedition.lcdui.Image;
/**
- * @author Sean Owen (srowen@google.com)
+ * <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 blackPoint;
private final int width;
private final int height;
+ 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) {
- int width = image.getWidth();
- int height = image.getHeight();
- this.width = width;
- this.height = height;
- int[] rgbPixels = new int[width * height];
- this.rgbPixels = rgbPixels;
+ public LCDUIImageMonochromeBitmapSource(Image image) {
+ width = image.getWidth();
+ height = image.getHeight();
+ rgbPixels = new int[width * height];
image.getRGB(rgbPixels, 0, width, 0, 0, width, height);
- int[] luminanceBuckets = new int[32];
- int minDimension = width < height ? width : height;
- for (int n = 0, offset = 0; n < minDimension; n++, offset += width + 1) {
- luminanceBuckets[computeRGBLuminance(rgbPixels[offset]) >> 3]++;
- }
- blackPoint = BlackPointEstimator.estimate(luminanceBuckets) << 3;
+ blackPoint = 0x7F;
+ lastMethod = null;
+ lastArgument = 0;
}
public boolean isBlack(int x, int y) {
}
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;
return width;
}
+ 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)) {
+ int minDimension = width < height ? width : height;
+ for (int n = 0, offset = 0; n < minDimension; n++, offset += width + 1) {
+ histogram[computeRGBLuminance(rgbPixels[offset]) >> LUMINANCE_SHIFT]++;
+ }
+ } else if (method.equals(BlackPointEstimationMethod.ROW_SAMPLING)) {
+ if (argument < 0 || argument >= height) {
+ throw new IllegalArgumentException("Row is not within the image: " + argument);
+ }
+ int offset = argument * width;
+ for (int x = 0; x < width; x++) {
+ histogram[computeRGBLuminance(rgbPixels[offset + x]) >> LUMINANCE_SHIFT]++;
+ }
+ } else {
+ throw new IllegalArgumentException("Unknown method: " + method);
+ }
+ blackPoint = BlackPointEstimator.estimate(histogram) << LUMINANCE_SHIFT;
+ lastMethod = method;
+ lastArgument = argument;
+ }
+ }
+
+ public BlackPointEstimationMethod getLastEstimationMethod() {
+ 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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projects / zxing.git / blobdiff