Switch to RGB-based captures for decoding, in preparation for move to continuous scan model

git-svn-id: https://zxing.googlecode.com/svn/trunk@262 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
srowen 2008-03-10 21:31:47 +00:00
parent 5f867e7b0d
commit 5f8beb71c6
3 changed files with 151 additions and 2 deletions

View file

@ -157,7 +157,7 @@ final class CameraManager {
params.topPixel = (cameraResolution.y - params.srcHeight) / 2;
params.outputWidth = stillResolution.x;
params.outputHeight = stillResolution.y;
params.dataFormat = 0; // YUV packed (planar would be better, but it doesn't work right now)
params.dataFormat = 2; // RGB565
}
String captureType = on ? "preview" : "still";
Log.v(TAG, "Setting params for " + captureType + ": srcWidth " + params.srcWidth +

View file

@ -0,0 +1,149 @@
/*
* Copyright (C) 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.client.android;
import android.graphics.Bitmap;
import com.google.zxing.BlackPointEstimationMethod;
import com.google.zxing.MonochromeBitmapSource;
import com.google.zxing.common.BitArray;
import com.google.zxing.common.BlackPointEstimator;
/**
* This object implements MonochromeBitmapSource around an Android Bitmap. Rather than capturing an
* RGB image and calculating the grey value at each pixel, we ask the camera driver for YUV data and
* strip out the luminance channel directly. This should be faster but provides fewer bits, i.e.
* fewer grey levels.
*
* @author dswitkin@google.com (Daniel Switkin)
* @author srowen@google.com (Sean Owen)
*/
final class RGBMonochromeBitmapSource implements MonochromeBitmapSource {
private final Bitmap image;
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;
RGBMonochromeBitmapSource(Bitmap image) {
this.image = image;
blackPoint = 0x7F;
lastMethod = null;
lastArgument = 0;
}
public boolean isBlack(int x, int y) {
return computeRGBLuminance(image.getPixel(x, y)) < blackPoint;
}
public BitArray getBlackRow(int y, BitArray row, int startX, int getWidth) {
if (row == null) {
row = new BitArray(getWidth);
} else {
row.clear();
}
int[] pixelRow = new int[getWidth];
image.getPixels(pixelRow, 0, getWidth, startX, y, getWidth, 1);
for (int i = 0; i < getWidth; i++) {
if (computeRGBLuminance(pixelRow[i]) < blackPoint) {
row.set(i);
}
}
return row;
}
public int getHeight() {
return image.height();
}
public int getWidth() {
return image.width();
}
public void estimateBlackPoint(BlackPointEstimationMethod method, int argument) {
if (!method.equals(lastMethod) || argument != lastArgument) {
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;
int startJ = width == minDimension ? 0 : (width - height) >> 1;
for (int n = 0; n < minDimension; n++) {
int pixel = image.getPixel(startJ + n, startI + n);
histogram[computeRGBLuminance(pixel) >> LUMINANCE_SHIFT]++;
}
} else if (method.equals(BlackPointEstimationMethod.ROW_SAMPLING)) {
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++) {
histogram[computeRGBLuminance(pixelRow[x]) >> LUMINANCE_SHIFT]++;
}
} else {
throw new IllegalArgumentException("Unknown method: " + method);
}
blackPoint = BlackPointEstimator.estimate(histogram, biasTowardsWhite) << 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;
}
/**
* 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) {
// 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) >> 8) +
((pixel & 0x0000FF00) << 1) +
((pixel & 0x000000FF) << 8)) >> 10;
}
}

View file

@ -67,7 +67,7 @@ final class WorkerThread extends Thread {
Bitmap bitmap = cameraManager.captureStill();
Result rawResult;
try {
MonochromeBitmapSource source = new YUVMonochromeBitmapSource(bitmap);
MonochromeBitmapSource source = new RGBMonochromeBitmapSource(bitmap);
rawResult = new MultiFormatReader().decode(source);
} catch (ReaderException e) {
Message message = Message.obtain(handler, R.id.decoding_failed_message);