Android 扫描二维码的实现(简化zxing)

来源:互联网 时间:1970-01-01

zxing

哎呀呀,在杭州2015 Hackthon的现场,因为没有二维码签到功能,被吐槽low!这是我近期最丢脸的事啦~
于是回来就开始着手开发二维码相关的东西了。

一搜索Google和我们SegmentFault,发现在Android上,Googlezxing这个二维码的库比较受欢迎,好,那就是它了(我就是这么任性= =)

OK,看下zxing这个项目https://github.com/zxing/zxing
好像非常大啊,如何快速用起来呢?

答案就是

简化!

简化的话,带来的副作用就是适用性降低,比如在这个场景里面,我们不考虑横屏的情况,不考虑对摄像头进行过多的配置,不存在截图。

简化过程

我们看下这个项目有一个android目录,它里面其实就是条码扫描器这个app的开源代码,因为我们暂时不需要深究它是如何进行图像识别,如何帮我们从图像里解析出二维码的,所以我们就不研究core相关的内容(但是里面都是干货啊!图像识别的干货啊!)


我们最主要就是参考这个里面的源码啦。

先把整个项目clone下来,然后把android这个源码导入到Android Studio里面去,经过小小的配置,就能搞定啦,直接运行我们就能看见这个App了。

先看下我们要做的工作是啥:

  1. 对摄像头进行管理(为了兼容老设备,我们要用即将被Google舍弃的android.hardware.camera类)。

  2. 对获取的一帧图片进行解析。

  3. 对解析的结果进行处理。

如果不带着问题或者目的去看源码的话,会非常没头绪,所以我们一定要记得我们想要做什么。

OK,先看第一个问题,我们需要对摄像头进行管理。我们可以看到目录中有三个文件和摄像机有关


就是这三个文件啦。

类用途CameraConfigurationManager这个类主要用于对摄像头进行一些配置,包括旋转角度、预览图尺寸等等CameraConfigurationUtils工具类,在CameraConfigurationManager调用,CameraManager控制摄像头的生命周期,获取预览尺寸,生成原始数据发送给解析器

在这里,我把CameraConfigurationUtils拷贝过来,另外两个类合成到CameraManager里面,在初始化的时候,做好配置。

摄像头的管理(横屏改竖屏)

因为原先zxing给的demo是横屏的,这里要改成竖屏,就需要做几个配置。

getFramingRectInPreview

getFramingRectInPreview这个函数中,cameraResolutionscreenResolution方向不对,所以

rect.left = rect.left * cameraResolution.y / screenResolution.x;rect.right = rect.right * cameraResolution.y / screenResolution.x;rect.top = rect.top * cameraResolution.x / screenResolution.y;rect.bottom = rect.bottom * cameraResolution.x / screenResolution.y;

这里需要把方向换一下。

binary data

还需要更改的地方,就是在获取帧预览中的原始数据,需要进行一个旋转,因为zxing原先是对横向的图片一行一行读取的,如果我们给予纵向的数据,就必须旋转数据,或者更改读取算法。 这里更改数据可能会更加方便,
buildLuminanceSource中,更改:

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];}int tmp = width;width = height;height = tmp;

最后记得把摄像头的预览旋转改成90°即可。

 camera.setDisplayOrientation(90);

附上这部分代码(比较长)

public class CameraManager {private static final int MIN_FRAME_WIDTH = 240;private static final int MIN_FRAME_HEIGHT = 240;// 这里修正扫描大小private static final int MAX_FRAME_WIDTH = 675; // = 5/8 * 1920private static final int MAX_FRAME_HEIGHT = 1200; // = 5/8 * 1080private Context mContext;private Point mScreenResolution;private Point mCameraResolution;private Point mBestPreviewSize;private Point mPreviewSizeOnScreen;private Rect mFramingRectInPreview;private Rect mFramingRect;private Camera mCamera;private PreviewCallback mPreviewCallback;private AutoFocusManager mAutoFocusManager;public CameraManager(Context context) {mContext = context;mPreviewCallback = new PreviewCallback(this);}public void openDriver(Camera camera, SurfaceHolder holder) {mCamera = camera;Camera.Parameters parameters = camera.getParameters();CameraConfigurationUtils.setBarcodeSceneMode(parameters);CameraConfigurationUtils.setFocus(parameters,true,true,false);Point theScreenResolution = new Point();Rect rect = holder.getSurfaceFrame();theScreenResolution.set(rect.height(), rect.width());mScreenResolution = theScreenResolution;mCameraResolution = CameraConfigurationUtils.findBestPreviewSizeValue(parameters, mScreenResolution);mBestPreviewSize = CameraConfigurationUtils.findBestPreviewSizeValue(parameters, mScreenResolution);boolean isScreenPortrait = mScreenResolution.x < mScreenResolution.y;boolean isPreviewSizePortrait = mBestPreviewSize.x < mBestPreviewSize.y;if (isScreenPortrait == isPreviewSizePortrait) {mPreviewSizeOnScreen = mBestPreviewSize;} else {mPreviewSizeOnScreen = new Point(mBestPreviewSize.y, mBestPreviewSize.x);}parameters.setPreviewSize(mBestPreviewSize.x, mBestPreviewSize.y);camera.setParameters(parameters);camera.setDisplayOrientation(90);Camera.Parameters afterParameters = camera.getParameters();Camera.Size afterSize = afterParameters.getPreviewSize();if (afterSize != null && (mBestPreviewSize.x != afterSize.width || mBestPreviewSize.y != afterSize.height)) {mBestPreviewSize.x = afterSize.width;mBestPreviewSize.y = afterSize.height;}}public synchronized Rect getFramingRect() {if (mFramingRect == null) {Point screenResolution = mScreenResolution;if (screenResolution == null) {// Called early, before init even finishedreturn null;}int width = findDesiredDimensionInRange(screenResolution.x, MIN_FRAME_WIDTH, MAX_FRAME_WIDTH);int height = findDesiredDimensionInRange(screenResolution.y, MIN_FRAME_HEIGHT, MAX_FRAME_HEIGHT);int leftOffset = (screenResolution.x - width) / 2;int topOffset = (screenResolution.y - height) / 2;mFramingRect = new Rect(leftOffset, topOffset, leftOffset + width, topOffset + height);}return mFramingRect;}public Point getCameraResolution() {return mCameraResolution;}public synchronized Rect getFramingRectInPreview() {if (mFramingRectInPreview == null) {Rect framingRect = getFramingRect();if (framingRect == null) {return null;}Rect rect = new Rect(framingRect);Point cameraResolution = mCameraResolution;Point screenResolution = mScreenResolution;if (cameraResolution == null || screenResolution == null) {// Called early, before init even finishedreturn null;}rect.left = rect.left * cameraResolution.y / screenResolution.x;rect.right = rect.right * cameraResolution.y / screenResolution.x;rect.top = rect.top * cameraResolution.x / screenResolution.y;rect.bottom = rect.bottom * cameraResolution.x / screenResolution.y;mFramingRectInPreview = rect;}return mFramingRectInPreview;}private static int findDesiredDimensionInRange(int resolution, int hardMin, int hardMax) {int dim = 5 * resolution / 8; // Target 5/8 of each dimensionif (dim < hardMin) {return hardMin;}if (dim > hardMax) {return hardMax;}return dim;}/** * A factory method to build the appropriate LuminanceSource object based on the format * of the preview buffers, as described by Camera.Parameters. * * @param data A preview frame. * @param width The width of the image. * @param height The height of the image. * @return A PlanarYUVLuminanceSource instance. */public PlanarYUVLuminanceSource buildLuminanceSource(byte[] data, int width, int height) {Rect rect = getFramingRectInPreview();if (rect == null) {return null;}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];}int tmp = width;width = height;height = tmp;// Go ahead and assume it's YUV rather than die.return new PlanarYUVLuminanceSource(rotatedData, width, height, rect.left, rect.top,rect.width(), rect.height(), false);}/** * A single preview frame will be returned to the handler supplied. The data will arrive as byte[] * in the message.obj field, with width and height encoded as message.arg1 and message.arg2, * respectively. * * @param handler The handler to send the message to. * @param message The what field of the message to be sent. */public synchronized void requestPreviewFrame(Handler handler, int message) {if (mCamera != null) {mPreviewCallback.setHandler(handler, message);mCamera.setOneShotPreviewCallback(mPreviewCallback);}}public synchronized void startPreview() {mCamera.startPreview();mAutoFocusManager = new AutoFocusManager(mContext, mCamera);}public synchronized void stopPreview() {if (mAutoFocusManager != null) {mAutoFocusManager.stop();mAutoFocusManager = null;}if (mCamera != null) {mCamera.stopPreview();}mPreviewCallback.setHandler(null, 0);}public synchronized void closeDriver() {mCamera.release();mCamera = null;}}

获取图像数据

Camera提供这么一个函数:setOneShotPreviewCallback,看名字就知道,它是会在某个时间点,回调你给的接口,然后传入一个二进制的图像数组,让你去解析,这正是我们想要的东西,所以我们看下这个PreviewCallback,它只有一个函数,

@Overridepublic void onPreviewFrame(byte[] data, Camera camera) {}

很显然,第一个参数就是图像数组了,我们看看zxing里面是怎么处理这个数据的。

解析数据

@Overridepublic void onPreviewFrame(byte[] data, Camera camera) {Point cameraResolution = mCameraManager.getCameraResolution();Handler thePreviewHandler = mPreviewHandler;if (cameraResolution != null && thePreviewHandler != null) {Message message = thePreviewHandler.obtainMessage(mPreviewMessage, cameraResolution.x,cameraResolution.y, data);message.sendToTarget();mPreviewHandler = null;} else {}}

zxing是发送到另外一个handler,也就是说,这个解析数据的过程比较浪费时间,所以要开线程来解决这个事。
我们跟踪这个previewHanlder可以发现,它是一个DecodeHandler,其中有个重要的decode函数

private void decode(byte[] data, int width, int height) {long start = System.currentTimeMillis();Result rawResult = null;PlanarYUVLuminanceSource source = activity.getCameraManager().buildLuminanceSource(data, width, height);if (source != null) {BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));try {rawResult = multiFormatReader.decodeWithState(bitmap);} catch (ReaderException re) {// continue} finally {multiFormatReader.reset();}}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) {Message message = Message.obtain(handler, R.id.decode_succeeded, rawResult);Bundle bundle = new Bundle();bundleThumbnail(source, bundle);message.setData(bundle);message.sendToTarget();}} else {if (handler != null) {Message message = Message.obtain(handler, R.id.decode_failed);message.sendToTarget();}}}

这里用到我们刚刚重写的buildLuminanceSource这个函数了,可以理解这个函数是对我们的原始数据做一个包装,来给解析器读取。

解析器的配置我们可以看看DecodeThread这个类(专门用于解析图像的线程)

... decodeFormats = EnumSet.noneOf(BarcodeFormat.class);decodeFormats.addAll(DecodeFormatManager.PRODUCT_FORMATS);decodeFormats.addAll(DecodeFormatManager.INDUSTRIAL_FORMATS);decodeFormats.addAll(DecodeFormatManager.QR_CODE_FORMATS);decodeFormats.addAll(DecodeFormatManager.DATA_MATRIX_FORMATS);mHints.put(DecodeHintType.POSSIBLE_FORMATS, decodeFormats);

这里我们可以为我们的扫描器加更多格式的支持(比如条形码、二维码、XX码)

zxing是使用List来管理这些解析器,然后每次读取数据,都经过这些解析器过滤一遍,如果解析成功就有结果,否则就没有结果。

最后我们跟踪R.id.decode_success找到CaptureActivityHandler
这里的handleMessage中有

 case R.id.decode_succeeded:state = State.SUCCESS;Bundle bundle = message.getData();Bitmap barcode = null;float scaleFactor = 1.0f;if (bundle != null) {byte[] compressedBitmap = bundle.getByteArray(DecodeThread.BARCODE_BITMAP);if (compressedBitmap != null) {barcode = BitmapFactory.decodeByteArray(compressedBitmap, 0, compressedBitmap.length, null);// Mutable copy:barcode = barcode.copy(Bitmap.Config.ARGB_8888, true);}scaleFactor = bundle.getFloat(DecodeThread.BARCODE_SCALED_FACTOR);}activity.handleDecode((Result) message.obj, barcode, scaleFactor);break;

我们读取Result对象的text成员变量就是我们想要的二维码信息了!最后的工作当然是解析我们的二维码中的URI,然后进行后续的工作啦~

PS: 附带二维码扫描的SegmentFault for Android版本 即将上线!!

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