biasTowardsWhite was, embarassingly, not accomplishing anything mathematically. It proved to not have much value so has been removed, to simplify the code.

git-svn-id: https://zxing.googlecode.com/svn/trunk@313 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
srowen 2008-03-26 14:42:33 +00:00
parent 5f1428308d
commit 7de539a67c
6 changed files with 49 additions and 21 deletions

View file

@ -83,7 +83,6 @@ final class RGBMonochromeBitmapSource implements MonochromeBitmapSource {
int width = image.width();
int height = image.height();
int[] histogram = new int[LUMINANCE_BUCKETS];
float biasTowardsWhite = 1.0f;
if (method.equals(BlackPointEstimationMethod.TWO_D_SAMPLING)) {
int minDimension = width < height ? width : height;
int startI = height == minDimension ? 0 : (height - width) >> 1;
@ -96,7 +95,6 @@ final class RGBMonochromeBitmapSource implements MonochromeBitmapSource {
if (argument < 0 || argument >= height) {
throw new IllegalArgumentException("Row is not within the image: " + argument);
}
biasTowardsWhite = 2.0f;
int[] pixelRow = new int[width];
image.getPixels(pixelRow, 0, width, 0, argument, width, 1);
for (int x = 0; x < width; x++) {
@ -105,7 +103,7 @@ final class RGBMonochromeBitmapSource implements MonochromeBitmapSource {
} else {
throw new IllegalArgumentException("Unknown method: " + method);
}
blackPoint = BlackPointEstimator.estimate(histogram, biasTowardsWhite) << LUMINANCE_SHIFT;
blackPoint = BlackPointEstimator.estimate(histogram) << LUMINANCE_SHIFT;
lastMethod = method;
lastArgument = argument;
}

View file

@ -85,7 +85,6 @@ final class YUVMonochromeBitmapSource implements MonochromeBitmapSource {
int width = image.width();
int height = image.height();
int[] histogram = new int[LUMINANCE_BUCKETS];
float biasTowardsWhite = 1.0f;
if (method.equals(BlackPointEstimationMethod.TWO_D_SAMPLING)) {
int minDimension = width < height ? width : height;
int startI = height == minDimension ? 0 : (height - width) >> 1;
@ -98,7 +97,6 @@ final class YUVMonochromeBitmapSource implements MonochromeBitmapSource {
if (argument < 0 || argument >= height) {
throw new IllegalArgumentException("Row is not within the image: " + argument);
}
biasTowardsWhite = 2.0f;
int[] pixelRow = new int[width];
image.getPixels(pixelRow, 0, width, 0, argument, width, 1);
for (int x = 0; x < width; x++) {
@ -107,7 +105,7 @@ final class YUVMonochromeBitmapSource implements MonochromeBitmapSource {
} else {
throw new IllegalArgumentException("Unknown method: " + method);
}
blackPoint = BlackPointEstimator.estimate(histogram, biasTowardsWhite) << LUMINANCE_SHIFT;
blackPoint = BlackPointEstimator.estimate(histogram) << LUMINANCE_SHIFT;
lastMethod = method;
lastArgument = argument;
}

View file

@ -40,18 +40,11 @@ public final class BlackPointEstimator {
* count of the brightest luminance values that should be considered "black".</p>
*
* @param histogram an array of <em>counts</em> of luminance values
* @param biasTowardsWhite values higher than 1.0 suggest that a higher black point is desirable (e.g.
* more values are considered black); less than 1.0 suggests that lower is desirable. Must be greater
* than 0.0; 1.0 is a good "default"
* @return index within argument of bucket corresponding to brightest values which should be
* considered "black"
* @throws ReaderException if "black" and "white" appear to be very close in luminance in the image
*/
public static int estimate(int[] histogram, float biasTowardsWhite) throws ReaderException{
if (Float.isNaN(biasTowardsWhite) || biasTowardsWhite <= 0.0f) {
throw new IllegalArgumentException("Illegal biasTowardsWhite: " + biasTowardsWhite);
}
public static int estimate(int[] histogram) throws ReaderException{
int numBuckets = histogram.length;
@ -99,7 +92,7 @@ public final class BlackPointEstimator {
int bestValley = secondPeak - 1;
int bestValleyScore = -1;
for (int i = secondPeak - 1; i > firstPeak; i--) {
int fromFirst = (int) (biasTowardsWhite * (i - firstPeak));
int fromFirst = i - firstPeak;
// Favor a "valley" that is not too close to either peak -- especially not the black peak --
// and that has a low value of course
int score = fromFirst * fromFirst * (secondPeak - i) * (256 - histogram[i]);

View file

@ -0,0 +1,43 @@
/*
* Copyright 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.zxing.common;
import com.google.zxing.ReaderException;
import junit.framework.TestCase;
/**
* @author srowen@google.com (Sean Owen)
*/
public final class BlackPointEstimationMethodTestCase extends TestCase {
public void testBasic() throws ReaderException {
int[] histogram = { 0, 0, 11, 43, 37, 18, 3, 1, 0, 0, 13, 36, 24, 0, 11, 2 };
int point = BlackPointEstimator.estimate(histogram);
assertEquals(8, point);
}
public void testTooLittleRange() {
try {
int[] histogram = { 0, 0, 0, 0, 0, 0, 1, 43, 48, 18, 3, 1, 0, 0, 0, 0 };
BlackPointEstimator.estimate(histogram);
fail("Should have thrown an exception");
} catch (ReaderException re) {
// good
}
}
}

View file

@ -81,7 +81,6 @@ public final class LCDUIImageMonochromeBitmapSource implements MonochromeBitmapS
public void estimateBlackPoint(BlackPointEstimationMethod method, int argument) throws ReaderException {
if (!method.equals(lastMethod) || argument != lastArgument) {
int[] histogram = new int[LUMINANCE_BUCKETS];
float biasTowardsWhite = 1.0f;
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) {
@ -91,7 +90,6 @@ public final class LCDUIImageMonochromeBitmapSource implements MonochromeBitmapS
if (argument < 0 || argument >= height) {
throw new IllegalArgumentException("Row is not within the image: " + argument);
}
biasTowardsWhite = 2.0f;
int offset = argument * width;
for (int x = 0; x < width; x++) {
histogram[computeRGBLuminance(rgbPixels[offset + x]) >> LUMINANCE_SHIFT]++;
@ -99,7 +97,7 @@ public final class LCDUIImageMonochromeBitmapSource implements MonochromeBitmapS
} else {
throw new IllegalArgumentException("Unknown method: " + method);
}
blackPoint = BlackPointEstimator.estimate(histogram, biasTowardsWhite) << LUMINANCE_SHIFT;
blackPoint = BlackPointEstimator.estimate(histogram) << LUMINANCE_SHIFT;
lastMethod = method;
lastArgument = argument;
}

View file

@ -88,7 +88,6 @@ public final class BufferedImageMonochromeBitmapSource implements MonochromeBitm
int width = image.getWidth();
int height = image.getHeight();
int[] histogram = new int[LUMINANCE_BUCKETS];
float biasTowardsWhite = 1.0f;
if (method.equals(BlackPointEstimationMethod.TWO_D_SAMPLING)) {
int minDimension = width < height ? width : height;
int startI = height == minDimension ? 0 : (height - width) >> 1;
@ -101,7 +100,6 @@ public final class BufferedImageMonochromeBitmapSource implements MonochromeBitm
if (argument < 0 || argument >= height) {
throw new IllegalArgumentException("Row is not within the image: " + argument);
}
biasTowardsWhite = 2.0f;
int[] rgbArray = new int[width];
image.getRGB(0, argument, width, 1, rgbArray, 0, width);
for (int x = 0; x < width; x++) {
@ -110,7 +108,7 @@ public final class BufferedImageMonochromeBitmapSource implements MonochromeBitm
} else {
throw new IllegalArgumentException("Unknown method: " + method);
}
blackPoint = BlackPointEstimator.estimate(histogram, biasTowardsWhite) << LUMINANCE_SHIFT;
blackPoint = BlackPointEstimator.estimate(histogram) << LUMINANCE_SHIFT;
lastMethod = method;
lastArgument = argument;
}