前言
目前市面上App携带的扫一扫功能大多是乞丐版，怎么说，就是只有扫一扫.而目前来说扫一扫做的最好的还是微信，微信有弱光环境的检测（可以自动提示用户打开闪光灯），同时，当发现扫描目标距离过远时，还可以自动的放大镜头，亲测可以多次的放大，所以说细节决定成败，支付宝虽然也有微信的功能，但是我觉得支付宝的弱光做的一般，自动放大也有点鸡肋，不过也很不错了，毕竟一般来说，实现扫一扫乞丐版就基本完事了，而我也遇到了这个需求，就是要实现微信和支付宝类似的效果.
效果图走一波（用的gif大师，录制的质量比较低，质量过高的传不上去，见谅）
第一帧gif当为弱光时，动态显示“手电筒”，点击打开后，一直显示“关系手电筒”.
第二个gif帧就是扫一扫自动放大的效果.
需求分析
1.中间的frame框就不说了，比较的简单，ondraw里边修改，用安卓纯纯的坐标系，就可以实现.
2.弱光检测: 这块我花了两天的时间研究，ios获取后置摄像头的光感比较的方便，几行代码就可以获取，他们的是brightnessvalue这个值；而安卓第一版我用的光传感器，你要知道，光传感器是在前置摄像头附近，而扫一扫是用后置摄像头来扫描的，光传感器晚上是没有问题的，白天不是非常的精确，就放弃了这个方案，最后查了相关的资料我使用jpegReader.metadata(),exifinterface来读取实时帧流，均以失败告终，我想Camera2应该提供了某些的api，但是要求是5.0之后了，我也就没有细研究，之后，我看到支付宝的效果后，我就明白了，他分析的是后摄像头拍照的图片颜色来区分的，多次尝试发现，是这样，同理，微信应该也是类似的实现，只不过他调的比较细，优化的比较好而已.
3.扫一扫自动放大:这个你思考下，其实也很简单，Camera有放大的属性，无非是触发条件怎么来判断，微信扫一扫是当镜头中有二维码的是才会进行自动放大，并且会多次的放大.
代码实现
我们项目用的是zxing,不用说了要修改源码.
ui层就不说了，真的简单，安卓坐标系，cavas 画布api，来绘制rect区域,在ViewFindView这个类里边的onDraw方法修改即可.
弱光检测
上面分析完后，就知道了，咱们要实时的分析图片的颜色值（agb值），既然说到了实时的分析，我们就要找到二维码处理解码实时帧的方法，zxing使用decodeThread,decodeHanlder,decodeThread线程不断的分析流并解码.
/** * Decode the data within the viewfinder rectangle, and time how long it took. For efficiency, * reuse the same reader objects from one decode to the next. * * @param data The YUV preview frame. * @param width The width of the preview frame. * @param height The height of the preview frame. */ private void decode(byte[] data, int width, int height)
这个data是YUV格式的，谷歌也提供了相关的转换方法Yuvimage.
将YUV转换为agb方法(网上摘抄，天下文章一大抄)
private int[] decodeYUV420SP(byte[] yuv420sp, int width, int height) {
final int frameSize = width * height;
int rgb[] = new int[width * height];
for (int j = 0, yp = 0; j < height; j++) {
int uvp = frameSize + (j >> 1) * width, u = 0, v = 0;
for (int i = 0; i < width; i++, yp++) {
int y = (0xff & ((int) yuv420sp[yp])) - 16;
if (y < 0) y = 0;
if ((i & 1) == 0) {
v = (0xff & yuv420sp[uvp++]) - 128;
u = (0xff & yuv420sp[uvp++]) - 128;
}
int y1192 = 1192 * y;
int r = (y1192 + 1634 * v);
int g = (y1192 - 833 * v - 400 * u);
int b = (y1192 + 2066 * u);
if (r < 0) r = 0;
else if (r > 262143) r = 262143;
if (g < 0) g = 0;
else if (g > 262143) g = 262143;
if (b < 0) b = 0;
else if (b > 262143) b = 262143;
rgb[yp] = 0xff000000 | ((r << 6) & 0xff0000) | ((g >> 2) &
0xff00) | ((b >> 10) & 0xff);
}
}
return rgb;
}使用Bitmap.createBitmap转换为bitmap图片下，分析图片颜色的平均值，颜色都是16进制的，不懂的可以网上搜下，黑色的颜色 对应int = -16777216, 所以我们认为当前的平均值 / black(-16777216) 小于等于1 同时大于0.99，就认为是弱光（这个值还可以调节）
private int getAverageColor(Bitmap bitmap) {
int redBucket = 0;
int greenBucket = 0;
int blueBucket = 0;
int pixelCount = 0;
for (int y = 0; y < bitmap.getHeight(); y++) {
for (int x = 0; x < bitmap.getWidth(); x++) {
int c = bitmap.getPixel(x, y);
pixelCount++;
redBucket += Color.red(c);
greenBucket += Color.green(c);
blueBucket += Color.blue(c);
}
}
int averageColor = Color.rgb(redBucket / pixelCount, greenBucket
/ pixelCount, blueBucket / pixelCount);
return averageColor;
}最终的方法，为了防止内存的溢出，取当前帧的八分之一宽高获取agb数组,同时用bmp的八分之一来分析颜色的平均值，分析完后直接释放bitmap.
//分析预览帧中图片的arg 取平均值
private void analysisColor(byte[] data, int width, int height) {
int[] rgb = decodeYUV420SP(data, width / 8, height / 8);
Bitmap bmp = Bitmap.createBitmap(rgb, width / 8, height / 8, Bitmap.Config.ARGB_8888);
if (bmp != null) {
//取以中心点宽高10像素的图片来分析
Bitmap resizeBitmap = Bitmap.createBitmap(bmp, bmp.getWidth() / 2, bmp.getHeight() / 2, 10, 10);
float color = (float) getAverageColor(resizeBitmap);
DecimalFormat decimalFormat1 = new DecimalFormat("0.00");
String percent = decimalFormat1.format(color / -16777216);
float floatPercent = Float.parseFloat(percent);
Constants.isWeakLight = floatPercent >= 0.99 && floatPercent <= 1.00;
if (null != resizeBitmap) {
resizeBitmap.recycle();
}
bmp.recycle();
}
}上述基本实现了弱光的检测，还可以进行微调，都是自己来控制的.
扫一扫自动放大的功能
二维码携带有坐标数据，根据坐标算出二维码的矩形大小并和当前frame边框的坐标进行比对，来进行放大，目前看微信好像也是这样实现的，不过弊端是什么，就是我是扫描出来这个界面结果后进行放大的，有点多此一举的感觉，目前先这样，后续可以根据时间来优化或修改吧.代码如下:
/*
* Copyright (C) 2010 ZXing authors
*
* 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 com.google.zxing.BinaryBitmap;
import com.google.zxing.DecodeHintType;
import com.google.zxing.MultiFormatReader;
import com.google.zxing.ReaderException;
import com.google.zxing.Result;
import com.google.zxing.common.Constants;
import com.google.zxing.common.HybridBinarizer;
import android.graphics.Bitmap;
import android.graphics.Color;
import android.graphics.Rect;
import android.hardware.Camera;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.Log;
import java.text.DecimalFormat;
import java.util.Map;
final class DecodeHandler extends Handler {
private static final String TAG = DecodeHandler.class.getSimpleName();
private final CaptureActivity activity;
private final MultiFormatReader multiFormatReader;
private boolean running = true;
private int frameCount;
DecodeHandler(CaptureActivity activity, Map<DecodeHintType, Object> hints) {
multiFormatReader = new MultiFormatReader();
multiFormatReader.setHints(hints);
this.activity = activity;
}
@Override
public void handleMessage(Message message) {
if (!running) {
return;
}
if (message.what == R.id.decode) {
decode((byte[]) message.obj, message.arg1, message.arg2);
} else if (message.what == R.id.quit) {
running = false;
Looper.myLooper().quit();
}
}
/**
* Decode the data within the viewfinder rectangle, and time how long it took. For efficiency,
* reuse the same reader objects from one decode to the next.
*
* @param data The YUV preview frame.
* @param width The width of the preview frame.
* @param height The height of the preview frame.
*/
private void decode(byte[] data, int width, int height) {
byte[] rotatedData = new byte[data.length];
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++)
rotatedData[x * height + height - y - 1] = data[x + y * width];
}
frameCount++;
//丢弃前2帧并每隔2帧分析下预览帧color值
if (frameCount > 2 && frameCount % 2 == 0) {
analysisColor(rotatedData, width, height);
}
long start = System.currentTimeMillis();
Result rawResult = null;
final PlanarYUVLuminanceSource source = activity.getCameraManager().buildLuminanceSource(rotatedData, height, width);
if (source != null) {
BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));
try {
rawResult = multiFormatReader.decodeWithState(bitmap);
} catch (ReaderException re) {
// continue
} finally {
multiFormatReader.reset();
}
}
final Handler handler = activity.getHandler();
if (rawResult != null) {
// Don't log the barcode contents for security.
long end = System.currentTimeMillis();
Log.d(TAG, "Found barcode in " + (end - start) + " ms");
if (handler != null) {
float point1X = rawResult.getResultPoints()[0].getX();
float point1Y = rawResult.getResultPoints()[0].getY();
float point2X = rawResult.getResultPoints()[1].getX();
float point2Y = rawResult.getResultPoints()[1].getY();
int len = (int) Math.sqrt(Math.abs(point1X - point2X) * Math.abs(point1X - point2X) + Math.abs(point1Y - point2Y) * Math.abs(point1Y - point2Y));
Rect frameRect = activity.getCameraManager().getFramingRect();
if (frameRect != null) {
int frameWidth = frameRect.right - frameRect.left;
Camera camera = activity.getCameraManager().getCameraNotStatic();
Camera.Parameters parameters = camera.getParameters();
final int maxZoom = parameters.getMaxZoom();
int zoom = parameters.getZoom();
if (parameters.isZoomSupported()) {
if (len <= frameWidth / 4) {
if (zoom == 0) {
zoom = maxZoom / 3;
} else {
zoom = zoom + 5;
}
if (zoom > maxZoom) {
zoom = maxZoom;
}
parameters.setZoom(zoom);
camera.setParameters(parameters);
final Result finalRawResult = rawResult;
postDelayed(new Runnable() {
@Override
public void run() {
Message message = Message.obtain(handler, R.id.decode_succeeded, finalRawResult);
Bundle bundle = new Bundle();
bundle.putParcelable(DecodeThread.BARCODE_BITMAP, source.renderCroppedGreyscaleBitmap());
message.setData(bundle);
message.sendToTarget();
}
}, 1000);
} else {
Message message = Message.obtain(handler, R.id.decode_succeeded, rawResult);
Bundle bundle = new Bundle();
bundle.putParcelable(DecodeThread.BARCODE_BITMAP, source.renderCroppedGreyscaleBitmap());
message.setData(bundle);
message.sendToTarget();
}
}
} else {
Message message = Message.obtain(handler, R.id.decode_succeeded, rawResult);
Bundle bundle = new Bundle();
bundle.putParcelable(DecodeThread.BARCODE_BITMAP, source.renderCroppedGreyscaleBitmap());
message.setData(bundle);
message.sendToTarget();
}
}
} else {
if (handler != null) {
Message message = Message.obtain(handler, R.id.decode_failed);
message.sendToTarget();
}
}
}
//分析预览帧中图片的arg 取平均值
private void analysisColor(byte[] data, int width, int height) {
int[] rgb = decodeYUV420SP(data, width / 8, height / 8);
Bitmap bmp = Bitmap.createBitmap(rgb, width / 8, height / 8, Bitmap.Config.ARGB_8888);
if (bmp != null) {
//取以中心点宽高10像素的图片来分析
Bitmap resizeBitmap = Bitmap.createBitmap(bmp, bmp.getWidth() / 2, bmp.getHeight() / 2, 10, 10);
float color = (float) getAverageColor(resizeBitmap);
DecimalFormat decimalFormat1 = new DecimalFormat("0.00");
String percent = decimalFormat1.format(color / -16777216);
float floatPercent = Float.parseFloat(percent);
Constants.isWeakLight = floatPercent >= 0.99 && floatPercent <= 1.00;
if (null != resizeBitmap) {
resizeBitmap.recycle();
}
bmp.recycle();
}
}
private int[] decodeYUV420SP(byte[] yuv420sp, int width, int height) {
final int frameSize = width * height;
int rgb[] = new int[width * height];
for (int j = 0, yp = 0; j < height; j++) {
int uvp = frameSize + (j >> 1) * width, u = 0, v = 0;
for (int i = 0; i < width; i++, yp++) {
int y = (0xff & ((int) yuv420sp[yp])) - 16;
if (y < 0) y = 0;
if ((i & 1) == 0) {
v = (0xff & yuv420sp[uvp++]) - 128;
u = (0xff & yuv420sp[uvp++]) - 128;
}
int y1192 = 1192 * y;
int r = (y1192 + 1634 * v);
int g = (y1192 - 833 * v - 400 * u);
int b = (y1192 + 2066 * u);
if (r < 0) r = 0;
else if (r > 262143) r = 262143;
if (g < 0) g = 0;
else if (g > 262143) g = 262143;
if (b < 0) b = 0;
else if (b > 262143) b = 262143;
rgb[yp] = 0xff000000 | ((r << 6) & 0xff0000) | ((g >> 2) &
0xff00) | ((b >> 10) & 0xff);
}
}
return rgb;
}
private int getAverageColor(Bitmap bitmap) {
int redBucket = 0;
int greenBucket = 0;
int blueBucket = 0;
int pixelCount = 0;
for (int y = 0; y < bitmap.getHeight(); y++) {
for (int x = 0; x < bitmap.getWidth(); x++) {
int c = bitmap.getPixel(x, y);
pixelCount++;
redBucket += Color.red(c);
greenBucket += Color.green(c);
blueBucket += Color.blue(c);
}
}
int averageColor = Color.rgb(redBucket / pixelCount, greenBucket
/ pixelCount, blueBucket / pixelCount);
return averageColor;
}
}作者：