本篇主要讲本科时做的一个应用&＃xff0c;人脸识别相册。主要包含JNI和业务逻辑。最终代码会公布在github。

算法部分

当时深度学习还没有很火&＃xff0c;所以用的是经典的PCA方法&＃xff0c;降维之后直接作为特征。人脸检测部分用的也是Opencv的Haar特征人脸检测。现在来看性能比较差了。这里就不介绍算法了&＃xff0c;感兴趣的可以看看我的其他博文。

系统架构

本次系统架构分成2部分&＃xff0c;一是算法&＃xff1b;二是界面和业务逻辑。算法部分由于是C&＃43;&＃43;写的&＃xff0c;所以需要用Java的JNI接口封装一下。界面方面采用瀑布流界面&＃xff0c;三栏极简风格。
业务逻辑是&＃xff1a;
1.用户打开相册&＃xff0c;自动读取系统照片&＃xff1b;
2.用户点击某一张图像&＃xff0c;若此照片此前未检测&＃xff0c;则检测人脸并提取特征&＃xff1b;若此照片此前已经检测&＃xff0c;则显示人脸位置。
3.用户点击人脸&＃xff0c;手工标注。
4.在第三栏&＃xff0c;按照人脸识别实现自动分类。
这个逻辑的缺点是一开始需要用户手动标记&＃xff0c;现在看来大概可以用聚类算法代替。

算法的JNI封装

因为我已经不做开发了&＃xff0c;所以现在并不知道JNI怎么写了&＃xff0c;已经不会写了。还是贴贴代码吧&＃xff1a;

package cn.edu.zju.srtp.facemap.algorithm;import java.io.File;
import java.util.Vector;import org.opencv.core.Mat;import android.content.Context;
import android.util.Log;public class NativeFaceRecognizer {public static final int LBPH_FACERECOGNIZER &＃61;1;public static final int FISHER_FACERECOGNIZER &＃61;2;public static final int EIGEN_FACERECOGNIZER &＃61;3;private final static String TAG &＃61;"NativeFaceRecognizer";public final static String LBPH_FILENAME &＃61;"lbph_model.xml";public final static String FISHER_FILENAME &＃61;"fisher_model.xml";public final static String EIGEN_FILENAME &＃61;"eigen_model.xml";/**Note which faceRecognizer has been created* */private int mState &＃61;1;/**The pointer to faceRecognizer with the initial value -1(important)* */private long mNativeObj &＃61;-1;private Context mContext;static{Log.d(TAG, "NativeFaceRecognizer static initial block enter");System.loadLibrary("opencv_java");System.loadLibrary("face_rec");Log.d(TAG, "NativeFaceRecognizer static initial block exit");}public NativeFaceRecognizer(Context context,int state) {mContext&＃61;context;mState&＃61;state;createFaceRecognizer();load();}/**Destroy the model first and create a FisherFaceRecognizer model.* */public void createFisherFaceRecognizer(){destroy();mState&＃61;FISHER_FACERECOGNIZER;mNativeObj&＃61;nativeCreateFisherFaceRecognizer();}/**Destroy the model first and create a LBPHFaceRecognizer model.* */public void createLBPHFaceRecognizer(){destroy();mState&＃61;LBPH_FACERECOGNIZER;mNativeObj&＃61;nativeCreateLBPHFaceRecognizer();}/**Destroy the model first and create a EigenFaceRecognizer model.* */public void createEigenFaceRecognizer(){destroy();mState&＃61;EIGEN_FACERECOGNIZER;mNativeObj&＃61;nativeCreateEigenFaceRecognizer();}/**Train the model.The input image should be grayscale.* The number of input images and labels should be equal.* &＃64;param images* &＃64;param labels_vec*/public void train(Vectorimages,Vectorlabels_vec){if(mNativeObj&＃61;&＃61;-1){Log.d(TAG,"Error:No faceRecognizer for training");return;}if(images.size()!&＃61;labels_vec.size()){Log.d(TAG, "The number of input images and labels are not eaual!");return;}//get the array of Mat addresslong imagesAddr[]&＃61;new long[images.size()];int i&＃61;0;int[]labels&＃61;new int[labels_vec.size()];for(Mat image:images){if(image.width()!&＃61;image.height()||image.channels()!&＃61;1||image.width()<&＃61;0){Log.d(TAG, "The intput images for training is illegal!" &＃43;"image.width&＃61;"&＃43;image.width()&＃43;" image.height&＃61;"&＃43;image.height()&＃43;"image.channels&＃61;"&＃43;image.channels());return;}imagesAddr[i]&＃61;image.getNativeObjAddr();labels[i]&＃61;labels_vec.elementAt(i).intValue();i&＃43;&＃43;;}nativeTrain(mNativeObj,imagesAddr,labels);}public int predict(Mat image){if(mNativeObj&＃61;&＃61;-1){Log.d(TAG,"Error:No faceRecognizer for predict.");return -1;}return nativePredict(mNativeObj,image.getNativeObjAddr());}/**Only LBPHfaceRecognizer can be updated.* * &＃64;param images* &＃64;param labels_vec*/public void update(Vectorimages,Vectorlabels_vec){if(mState!&＃61;LBPH_FACERECOGNIZER){Log.d(TAG,"Error:This kind of model"&＃43;" cannot be updated.");return;}if(mNativeObj&＃61;&＃61;-1){Log.d(TAG,"Error:No faceRecognizer for model update.");createLBPHFaceRecognizer();}//get the array of Mat addresslong imagesAddr[]&＃61;new long[images.size()];int i&＃61;0;int[]labels&＃61;new int[labels_vec.size()];for(Mat image:images){if(image.width()!&＃61;image.height()||image.channels()!&＃61;1||image.width()<&＃61;0){Log.d(TAG, "The intput images for training is illegal!" &＃43;"image.width&＃61;"&＃43;image.width()&＃43;" image.height&＃61;"&＃43;image.height()&＃43;"image.channels&＃61;"&＃43;image.channels());return;}imagesAddr[i]&＃61;image.getNativeObjAddr();labels[i]&＃61;labels_vec.elementAt(i).intValue();i&＃43;&＃43;;}nativeUpdate(mNativeObj, imagesAddr, labels);return;}/**Save the model to file.* */public void save(){if(mNativeObj&＃61;&＃61;-1){Log.d(TAG,"Error:No faceRecognizer to save");return;}String path&＃61;mContext.getFilesDir()&＃43;"/"&＃43;getFileName();nativeSave(mNativeObj, path);}public void load(){if(mNativeObj&＃61;&＃61;-1){Log.d(TAG,"Error:No faceRecognizer to load");return;}String path&＃61;mContext.getFilesDir()&＃43;"/"&＃43;getFileName();File f&＃61;new File(path);if(f.exists()){try{nativeLoad(mNativeObj, path);}catch(Exception e){Log.d(TAG,"load file Alert:model doesn&＃39;t exists.");}}}public void destroy(){if(mNativeObj!&＃61;-1){nativeDestroyObject(mNativeObj);mNativeObj&＃61;-1;}else{Log.d(TAG,"Cannot delete an illegal pointer");}}/***Clear the model file. */public Boolean clear(){String fileName&＃61;getFileName();File f&＃61;new File(mContext.getFilesDir()&＃43;"/"&＃43;fileName);if(f.exists()){return mContext.deleteFile(fileName); }return false;}private String getFileName(){String fileName&＃61;new String();if(mState&＃61;&＃61;LBPH_FACERECOGNIZER){fileName&＃61;LBPH_FILENAME;}else if(mState&＃61;&＃61;FISHER_FACERECOGNIZER){fileName&＃61;FISHER_FILENAME;}else if(mState&＃61;&＃61;EIGEN_FACERECOGNIZER){fileName&＃61;EIGEN_FILENAME;}else{return null;}return fileName;}private void createFaceRecognizer(){if(mState&＃61;&＃61;LBPH_FACERECOGNIZER){createLBPHFaceRecognizer(); }else if(mState&＃61;&＃61;FISHER_FACERECOGNIZER){createFisherFaceRecognizer();}else if(mState&＃61;&＃61;EIGEN_FACERECOGNIZER){createEigenFaceRecognizer();}}public int getState(){return mState;}private static native long nativeCreateFisherFaceRecognizer();private static native long nativeCreateLBPHFaceRecognizer();private static native long nativeCreateEigenFaceRecognizer();private static native void nativeTrain(long thiz,long[]images,int[]labels);private static native void nativeUpdate(long thiz,long[]images,int[]labels);private static native int nativePredict(long thiz,long image);private static native void nativeSave(long thiz,String fileName);private static native void nativeLoad(long thiz,String fileName);private static native void nativeDestroyObject(long thiz);}


依稀记得当时写这个碰到了一些问题。主要的问题是&＃xff0c;我在C&＃43;&＃43;里写的类&＃xff0c;需要动态分配&＃xff0c;然后把它的指针保存在Java里。每次Java把这个指针再传给C&＃43;&＃43;。这种方式是以Java为主的编程方式。不知道还有没有其他更好的写法。

图像缩放

当时为了实现图像缩放&＃xff0c;在图书馆写了一上午。主要觉得挺好玩的。年少。

package cn.edu.zju.srtp.facemap.album;import java.util.ArrayList;
import java.util.Calendar;import org.opencv.core.Rect;import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.text.format.Time;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import cn.edu.zju.srtp.facemap.R;
import cn.edu.zju.srtp.facemap.algorithm.Face;
import cn.edu.zju.srtp.facemap.algorithm.FaceRecManagerSingleInstance;public class ZoomImageView extends View{private static final String TAG &＃61;"ZoomImageView";/** * 初始化状态常量 */ public static final int STATUS_INIT &＃61; 1; /** * 图片放大状态常量 */ public static final int STATUS_ZOOM_OUT &＃61; 2; /** * 图片缩小状态常量 */ public static final int STATUS_ZOOM_IN &＃61; 3; /** * 图片拖动状态常量 */ public static final int STATUS_MOVE &＃61; 4; /** * 用于对图片进行移动和缩放变换的矩阵 */ private Matrix matrix &＃61; new Matrix(); /** * 待展示的Bitmap对象 */ private Bitmap sourceBitmap;/***图片边框 */private Bitmap borderBitmap;/** * 记录当前操作的状态&＃xff0c;可选值为STATUS_INIT、STATUS_ZOOM_OUT、STATUS_ZOOM_IN和STATUS_MOVE */ private int currentStatus; private ArrayList mFaces&＃61;new ArrayList();private int mInSampleSize &＃61;1;private Paint mPaint&＃61;new Paint();private Bitmap mBackground;private Time mTime &＃61;new Time();private long mStartTime;private Face mFaceClicked;/** * ZoomImageView控件的宽度 */ private int width; /** * ZoomImageView控件的高度 */ private int height; /** * 记录两指同时放在屏幕上时&＃xff0c;中心点的横坐标值 */ private float centerPointX; /** * 记录两指同时放在屏幕上时&＃xff0c;中心点的纵坐标值 */ private float centerPointY; /** * 记录当前图片的宽度&＃xff0c;图片被缩放时&＃xff0c;这个值会一起变动 */ private float currentBitmapWidth; /** * 记录当前图片的高度&＃xff0c;图片被缩放时&＃xff0c;这个值会一起变动 */ private float currentBitmapHeight; /** * 记录上次手指移动时的横坐标 */ private float lastXMove &＃61; -1; /** * 记录上次手指移动时的纵坐标 */ private float lastYMove &＃61; -1; /** * 记录手指在横坐标方向上的移动距离 */ private float movedDistanceX; /** * 记录手指在纵坐标方向上的移动距离 */ private float movedDistanceY; /** * 记录图片在矩阵上的横向偏移值 */ private float totalTranslateX; /** * 记录图片在矩阵上的纵向偏移值 */ private float totalTranslateY; /** * 记录图片在矩阵上的总缩放比例 */ private float totalRatio; /** * 记录手指移动的距离所造成的缩放比例 */ private float scaledRatio; /** * 记录图片初始化时的缩放比例 */ private float initRatio; /** * 记录上次两指之间的距离 */ private double lastFingerDis; /** * ZoomImageView构造函数&＃xff0c;将当前操作状态设为STATUS_INIT。 * * &＃64;param context * &＃64;param attrs */ public ZoomImageView(Context context, AttributeSet attrs) { super(context, attrs); currentStatus &＃61; STATUS_INIT; mPaint.setColor(Color.WHITE);mPaint.setStrokeWidth(2);mPaint.setStyle(Paint.Style.STROKE);borderBitmap&＃61;BitmapFactory.decodeResource(getResources(), R.drawable.picture_frame_default);} /** * 将待展示的图片设置进来。 * * &＃64;param bitmap * 待展示的Bitmap对象 */ public void setImageBitmap(Bitmap bitmap) { sourceBitmap &＃61; bitmap; invalidate(); } public void setInSampleSize(int inSampleSize){mInSampleSize&＃61;inSampleSize;}public void setFaces(ArrayListfaces){mFaces&＃61;(ArrayList) faces.clone();invalidate();}&＃64;Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { super.onLayout(changed, left, top, right, bottom); if (changed) { // 分别获取到ZoomImageView的宽度和高度 width &＃61; getWidth(); height &＃61; getHeight(); } } &＃64;Override public boolean onTouchEvent(MotionEvent event) { if(totalRatio>initRatio){ getParent().requestDisallowInterceptTouchEvent(true);}else{getParent().requestDisallowInterceptTouchEvent(false); }switch (event.getActionMasked()) { case MotionEvent.ACTION_POINTER_DOWN: if (event.getPointerCount() &＃61;&＃61; 2) { // 当有两个手指按在屏幕上时&＃xff0c;计算两指之间的距离 lastFingerDis &＃61; distanceBetweenFingers(event); }break; case MotionEvent.ACTION_DOWN:
// mTime.setToNow();mStartTime&＃61;Calendar.getInstance().getTimeInMillis();case MotionEvent.ACTION_MOVE: if (event.getPointerCount() &＃61;&＃61; 1) { // 只有单指按在屏幕上移动时&＃xff0c;为拖动状态 float xMove &＃61; event.getX(); float yMove &＃61; event.getY(); if (lastXMove &＃61;&＃61; -1 && lastYMove &＃61;&＃61; -1) { lastXMove &＃61; xMove; lastYMove &＃61; yMove; } currentStatus &＃61; STATUS_MOVE;movedDistanceX &＃61; xMove - lastXMove; movedDistanceY &＃61; yMove - lastYMove; // 进行边界检查&＃xff0c;不允许将图片拖出边界 if (totalTranslateX &＃43; movedDistanceX > 0) { movedDistanceX &＃61; 0; } else if (width - (totalTranslateX &＃43; movedDistanceX) > currentBitmapWidth) { movedDistanceX &＃61; 0; } if (totalTranslateY &＃43; movedDistanceY > 0) { movedDistanceY &＃61; 0; } else if (height - (totalTranslateY &＃43; movedDistanceY) > currentBitmapHeight) { movedDistanceY &＃61; 0; } // 调用onDraw()方法绘制图片 invalidate(); lastXMove &＃61; xMove; lastYMove &＃61; yMove; }else if(event.getPointerCount() &＃61;&＃61; 2){// 有两个手指按在屏幕上移动时&＃xff0c;为缩放状态 centerPointBetweenFingers(event); double fingerDis &＃61; distanceBetweenFingers(event); if (fingerDis > lastFingerDis) { currentStatus &＃61; STATUS_ZOOM_OUT; } else { currentStatus &＃61; STATUS_ZOOM_IN; } // 进行缩放倍数检查&＃xff0c;最大只允许将图片放大4倍&＃xff0c;最小可以缩小到初始化比例 if ((currentStatus &＃61;&＃61; STATUS_ZOOM_OUT && totalRatio <4 * initRatio) || (currentStatus &＃61;&＃61; STATUS_ZOOM_IN && totalRatio > initRatio)) { scaledRatio &＃61; (float) (fingerDis / lastFingerDis); totalRatio &＃61; totalRatio * scaledRatio;if (totalRatio > 4 * initRatio) { totalRatio &＃61; 4 * initRatio; } else if (totalRatio // 调用onDraw()方法绘制图片 invalidate(); lastFingerDis &＃61; fingerDis; }}break;case MotionEvent.ACTION_POINTER_UP:if (event.getPointerCount() &＃61;&＃61; 2) { // 手指离开屏幕时将临时值还原 lastXMove &＃61; -1; lastYMove &＃61; -1; } break; case MotionEvent.ACTION_UP: // 手指离开屏幕时将临时值还原 lastXMove &＃61; -1; lastYMove &＃61; -1; //Time t&＃61;new Time();//t.setToNow();long t&＃61;Calendar.getInstance().getTimeInMillis();if(t-mStartTime>&＃61;100){break;}float fX&＃61;event.getX();float fY&＃61;event.getY();mFaceClicked&＃61;null;for(Face f:mFaces){Rect faceRect&＃61;f.getFaceRect();float left&＃61;faceRect.x*totalRatio/mInSampleSize&＃43;totalTranslateX;float top&＃61;faceRect.y*totalRatio/mInSampleSize&＃43;totalTranslateY;float right&＃61;(faceRect.x&＃43;faceRect.width)*totalRatio/mInSampleSize&＃43;totalTranslateX;float bottom&＃61;(faceRect.y&＃43;faceRect.height)*totalRatio/mInSampleSize&＃43;totalTranslateY;if(fX>&＃61;left&&fX<&＃61;right&&fY>&＃61;top&&fY<&＃61;bottom){mFaceClicked&＃61;f;}}final Face face&＃61;mFaceClicked;if(face&＃61;&＃61;null)break;invalidate();if(face.getPeopleName()&＃61;&＃61;null){final EditText mText &＃61; new EditText(getContext());AlertDialog.Builder builder &＃61; new AlertDialog.Builder(getContext());builder.setTitle("请输入名字").setIcon(android.R.drawable.ic_dialog_info).setView(mText).setPositiveButton("确定",new DialogInterface.OnClickListener() {&＃64;Overridepublic void onClick(DialogInterface dialog,int which) {FaceRecManagerSingleInstance.getInstance(getContext()).update(face.getFaceId(),mText.getText().toString());invalidate();}}).setNegativeButton("取消", null).show();}else{AlertDialog.Builder builder &＃61; new AlertDialog.Builder(getContext());builder.setMessage("这是 " &＃43; face.getPeopleName() &＃43; " 吗&＃xff1f;").setIcon(android.R.drawable.ic_dialog_info).setPositiveButton("是",new DialogInterface.OnClickListener() {&＃64;Overridepublic void onClick(DialogInterface dialog,int which) {FaceRecManagerSingleInstance.getInstance(getContext()).update(face.getFaceId(),face.getPeopleName());invalidate();}}).setNegativeButton("不是",new DialogInterface.OnClickListener() {&＃64;Overridepublic void onClick(DialogInterface dialog,int which) {final EditText mText &＃61; new EditText(getContext());AlertDialog.Builder builder &＃61; new AlertDialog.Builder(getContext()); builder.setTitle("请输入名字").setIcon(android.R.drawable.ic_dialog_info).setView(mText).setPositiveButton("确定",new DialogInterface.OnClickListener() {&＃64;Overridepublic void onClick(DialogInterface dialog,int which) {FaceRecManagerSingleInstance.getInstance(getContext()).update(face.getFaceId(),mText.getText().toString());invalidate();}}).setNegativeButton("取消",null).show();}}).show();} break; default: break; }return true;}public Bitmap getSrcBitmap(){return sourceBitmap;}private void drawFaces(Canvas canvas){Log.d(TAG,"drawFaces");for(Face face:mFaces){Rect faceRect&＃61;face.getFaceRect();float left&＃61;faceRect.x*totalRatio/mInSampleSize&＃43;totalTranslateX;float top&＃61;faceRect.y*totalRatio/mInSampleSize&＃43;totalTranslateY;float right&＃61;(faceRect.x&＃43;faceRect.width)*totalRatio/mInSampleSize&＃43;totalTranslateX;float bottom&＃61;(faceRect.y&＃43;faceRect.height)*totalRatio/mInSampleSize&＃43;totalTranslateY;if(!face.getVerified()){mPaint.setColor(Color.GREEN);}if(face.equals(mFaceClicked)){mPaint.setColor(Color.YELLOW);mFaceClicked&＃61;null;}canvas.drawRect(left,top,right,bottom, mPaint);if(face.getPeopleName()!&＃61;null){mPaint.setTextSize((float) ((right-left)*0.15));mPaint.setStrokeWidth(0);canvas.drawText(face.getPeopleName(),left ,top-4, mPaint);mPaint.setStrokeWidth(2);}mPaint.setColor(Color.WHITE);}}/** * 根据currentStatus的值来决定对图片进行什么样的绘制操作。 */ &＃64;Override protected void onDraw(Canvas canvas) { try{ super.onDraw(canvas);switch (currentStatus) { case STATUS_ZOOM_OUT: case STATUS_ZOOM_IN: zoom(canvas); break;case STATUS_MOVE: move(canvas); break; case STATUS_INIT: initBitmap(canvas); default: canvas.drawBitmap(sourceBitmap, matrix, null);drawFaces(canvas);break; }}catch(Exception e){Log.e(TAG,"Error in onDraw:",e);}}/** * 对图片进行缩放处理。 * * &＃64;param canvas */ private void zoom(Canvas canvas) { matrix.reset(); // 将图片按总缩放比例进行缩放 matrix.postScale(totalRatio, totalRatio); float scaledWidth &＃61; sourceBitmap.getWidth() * totalRatio; float scaledHeight &＃61; sourceBitmap.getHeight() * totalRatio; float translateX &＃61; 0f; float translateY &＃61; 0f; // 如果当前图片宽度小于屏幕宽度&＃xff0c;则按屏幕中心的横坐标进行水平缩放。//否则按两指的中心点的横坐标进行水平缩放if (currentBitmapWidth 2f; } else { translateX &＃61; totalTranslateX * scaledRatio &＃43; centerPointX * (1 - scaledRatio); // 进行边界检查&＃xff0c;保证图片缩放后在水平方向上不会偏移出屏幕 if (translateX > 0) { translateX &＃61; 0; } else if (width - translateX > scaledWidth) { translateX &＃61; width - scaledWidth; } } // 如果当前图片高度小于屏幕高度&＃xff0c;则按屏幕中心的纵//坐标进行垂直缩放。否则按两指的中心点的纵坐标进行垂直缩放if (currentBitmapHeight 2f; }else{translateY &＃61; totalTranslateY * scaledRatio &＃43; centerPointY * (1 - scaledRatio); // 进行边界检查&＃xff0c;保证图片缩放后在垂直方向上不会偏移出屏幕 if (translateY > 0) { translateY &＃61; 0; } else if (height - translateY > scaledHeight) { translateY &＃61; height - scaledHeight; } }// 缩放后对图片进行偏移&＃xff0c;以保证缩放后中心点位置不变 matrix.postTranslate(translateX, translateY); totalTranslateX &＃61; translateX; totalTranslateY &＃61; translateY; currentBitmapWidth &＃61; scaledWidth; currentBitmapHeight &＃61; scaledHeight; canvas.drawBitmap(sourceBitmap, matrix, null); drawFaces(canvas);}/** * 对图片进行平移处理 * * &＃64;param canvas */ private void move(Canvas canvas) { matrix.reset(); // 根据手指移动的距离计算出总偏移值 float translateX &＃61; totalTranslateX &＃43; movedDistanceX; float translateY &＃61; totalTranslateY &＃43; movedDistanceY; // 先按照已有的缩放比例对图片进行缩放 matrix.postScale(totalRatio, totalRatio); // 再根据移动距离进行偏移 matrix.postTranslate(translateX, translateY); totalTranslateX &＃61; translateX; totalTranslateY &＃61; translateY; canvas.drawBitmap(sourceBitmap, matrix, null); drawFaces(canvas);}/** * 对图片进行初始化操作&＃xff0c;包括让图片居中&＃xff0c;以及当图片大于屏幕宽高时对图片进行压缩。 * * &＃64;param canvas */ private void initBitmap(Canvas canvas) { if (sourceBitmap !&＃61; null) { matrix.reset(); int bitmapWidth &＃61; sourceBitmap.getWidth(); int bitmapHeight &＃61; sourceBitmap.getHeight(); if (bitmapWidth > width || bitmapHeight > height) { if (bitmapWidth - width > bitmapHeight - height) { // 当图片宽度大于屏幕宽度时&＃xff0c;将图片等比例压缩&＃xff0c;使它可以完全显示出来 float ratio &＃61; width / (bitmapWidth * 1.0f); matrix.postScale(ratio, ratio); float translateY &＃61; (height - (bitmapHeight * ratio)) / 2f; // 在纵坐标方向上进行偏移&＃xff0c;以保证图片居中显示 matrix.postTranslate(0, translateY); totalTranslateY &＃61; translateY; totalRatio &＃61; initRatio &＃61; ratio; }else { // 当图片高度大于屏幕高度时&＃xff0c;将图片等比例压缩&＃xff0c;使它可以完全显示出来 float ratio &＃61; height / (bitmapHeight * 1.0f); matrix.postScale(ratio, ratio); float translateX &＃61; (width - (bitmapWidth * ratio)) / 2f; // 在横坐标方向上进行偏移&＃xff0c;以保证图片居中显示 matrix.postTranslate(translateX, 0); totalTranslateX &＃61; translateX; totalRatio &＃61; initRatio &＃61; ratio; }currentBitmapWidth &＃61; bitmapWidth * initRatio; currentBitmapHeight &＃61; bitmapHeight * initRatio;}else{// 当图片的宽高都小于屏幕宽高时&＃xff0c;直接让图片居中显示 float translateX &＃61; (width - sourceBitmap.getWidth()) / 2f; float translateY &＃61; (height - sourceBitmap.getHeight()) / 2f; matrix.postTranslate(translateX, translateY); totalTranslateX &＃61; translateX; totalTranslateY &＃61; translateY; totalRatio &＃61; initRatio &＃61; 1f; currentBitmapWidth &＃61; bitmapWidth; currentBitmapHeight &＃61; bitmapHeight; }canvas.drawBitmap(sourceBitmap, matrix, null); drawFaces(canvas);} }/** * 计算两个手指之间的距离。 * * &＃64;param event * &＃64;return 两个手指之间的距离 */ private double distanceBetweenFingers(MotionEvent event) { float disX &＃61; Math.abs(event.getX(0) - event.getX(1)); float disY &＃61; Math.abs(event.getY(0) - event.getY(1)); return Math.sqrt(disX * disX &＃43; disY * disY); } /** * 计算两个手指之间中心点的坐标。 * * &＃64;param event */ private void centerPointBetweenFingers(MotionEvent event) { float xPoint0 &＃61; event.getX(0); float yPoint0 &＃61; event.getY(0); float xPoint1 &＃61; event.getX(1); float yPoint1 &＃61; event.getY(1); centerPointX &＃61; (xPoint0 &＃43; xPoint1) / 2; centerPointY &＃61; (yPoint0 &＃43; yPoint1) / 2; }
}


存在的问题

瀑布流渲染似乎有点慢&＃xff0c;要等很久的样子。有时候闪退。