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,Google
的zxing
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:
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)。对获取的一帧图片进行解析。
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
在getFramingRectInPreview
这个函数中,cameraResolution
和screenResolution
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,
在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 * 1920
private static final int MAX_FRAME_HEIGHT = 1200; // = 5/8 * 1080
private 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 finished
return 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 finished
return 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 dimension
if (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,
@Override
public 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
@Override
public 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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