网站建设费用怎么做分录,家装设计师怎么学,网络营销师考试内容,前端如何做能切换语言的网站OCR是一个很常用的功能#xff0c;Google ML Kit提供了OCR能力#xff0c;用起来也很简单#xff0c;本文介绍一下使用方法。
1. 相关概念
名词概念解释TextBlock块一个段落Line行一行文本Element元素单词#xff1b;对汉字来说#xff0c;类似开头 (分隔符)中间Google ML Kit提供了OCR能力用起来也很简单本文介绍一下使用方法。
1. 相关概念
名词概念解释TextBlock块一个段落Line行一行文本Element元素单词对汉字来说类似开头 (分隔符)中间分隔符 结尾这样含有明显分隔符的才会有多个字在一个Element中否则就是单个字Symbol字符字母对汉字来说就是单个字
2. 代码实现
在build.gradle中添加相关依赖
// To recognize Chinese script
implementation com.google.mlkit:text-recognition-chinese:16.0.1添加布局文件activity_ocr.xml
?xml version1.0 encodingutf-8?
LinearLayout xmlns:androidhttp://schemas.android.com/apk/res/androidandroid:layout_widthmatch_parentandroid:layout_heightmatch_parentandroid:orientationverticalFrameLayoutandroid:layout_widthwrap_contentandroid:layout_heightwrap_contentSurfaceViewandroid:idid/camera_previewandroid:layout_widthwrap_contentandroid:layout_heightwrap_content /com.example.study.views.DrawViewandroid:idid/ocr_areaandroid:layout_widthwrap_contentandroid:layout_heightwrap_content //FrameLayoutButtonandroid:idid/ocr_switchandroid:layout_widthmatch_parentandroid:layout_heightmatch_parentandroid:layout_gravitycenter_horizontal|bottomandroid:layout_marginBottom80dpandroid:backgroundcolor/夏云灰android:textstop /
/LinearLayout绘制文字的OCRDrawView.java
package com.example.study.views;import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Point;
import android.util.AttributeSet;
import android.view.View;import androidx.annotation.Nullable;import java.util.ArrayList;
import java.util.List;public class OCRDrawView extends View {private final Object lock new Object();protected Paint paint new Paint();protected Path path new Path();private final ListShapeInfo cornerPointsList new ArrayList();public OCRDrawView(Context context) {super(context);}public OCRDrawView(Context context, Nullable AttributeSet attrs) {super(context, attrs);}public void clear() {synchronized (lock) {cornerPointsList.clear();}postInvalidate();}public void add(Point[] cornerPoints, String text) {synchronized (lock) {cornerPointsList.add(new ShapeInfo(cornerPoints, text));}}Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);synchronized (lock) {for (ShapeInfo shapeInfo : cornerPointsList) {drawBackground(shapeInfo, canvas);drawText(shapeInfo, canvas);}}}private void drawText(ShapeInfo shapeInfo, Canvas canvas) {Point[] points shapeInfo.points;// 根据矩形区域的高度设置文字大小double height calDistance(points[0], points[3]);double width calDistance(points[2], points[3]);float textSize (float) Math.min(height, width / shapeInfo.text.length());paint.setColor(Color.BLUE);paint.setTextSize(textSize);path.reset();path.moveTo(points[3].x, points[3].y);path.lineTo(points[2].x, points[2].y);canvas.drawTextOnPath(shapeInfo.text, path, 0, 0, paint);}private double calDistance(Point start, Point end) {return Math.sqrt(Math.pow(start.x - end.x, 2) Math.pow(start.y - end.y, 2));}private void drawBackground(ShapeInfo shapeInfo, Canvas canvas) {Point[] shape shapeInfo.points;path.reset();path.moveTo(shape[3].x, shape[3].y);for (int i 0; i shape.length; i) {path.lineTo(shape[i].x, shape[i].y);}path.close();paint.setColor(Color.WHITE);canvas.drawPath(path, paint);}static class ShapeInfo {Point[] points;String text;public ShapeInfo(Point[] shape, String text) {this.points shape;this.text text;}}
}activity类
package com.example.study.activities;import android.Manifest;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.ImageFormat;
import android.graphics.Matrix;
import android.graphics.Point;
import android.graphics.Rect;
import android.graphics.YuvImage;
import android.hardware.Camera;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.Toast;import androidx.activity.ComponentActivity;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;import com.example.study.R;
import com.example.study.views.OCRDrawView;
import com.google.mlkit.vision.text.Text;
import com.google.mlkit.vision.text.TextRecognition;
import com.google.mlkit.vision.text.TextRecognizer;
import com.google.mlkit.vision.text.chinese.ChineseTextRecognizerOptions;import java.io.ByteArrayOutputStream;public class OCRActivity extends ComponentActivity implements Camera.PreviewCallback, SurfaceHolder.Callback {private static final String TAG CameraDemoActivity;private static final int REQUEST_CAMERA 1000;private static final int HEIGHT 1920;private static final int WIDTH 1080;private static final int ORIENTATION 90;private SurfaceView preview;private OCRDrawView ocrArea;private Button ocrSwitch;private Camera camera;private Camera.Parameters parameters;private TextRecognizer recognizer;private Matrix matrix;private boolean isRecognizering false;private boolean stopRecognizer false;Overrideprotected void onCreate(Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);this.setContentView(R.layout.activity_ocr);initView();initVar();// 检查权限if (checkSelfPermission(Manifest.permission.CAMERA) ! PackageManager.PERMISSION_GRANTED) {requestPermissions(new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA);} else {preview.getHolder().addCallback(this);}}private void initVar() {recognizer TextRecognition.getClient(new ChineseTextRecognizerOptions.Builder().build());matrix new Matrix();matrix.setRotate(ORIENTATION);// 4个角的坐标是没有旋转过的所以HEIGHT、WIDTH是反的matrix.preTranslate(-HEIGHT 1, -WIDTH 1);}private void initView() {preview findViewById(R.id.camera_preview);ocrArea findViewById(R.id.ocr_area);ocrSwitch findViewById(R.id.ocr_switch);ocrSwitch.setOnClickListener(view - {stopRecognizer !stopRecognizer;ocrSwitch.setText(stopRecognizer ? start : stop);if (camera null) {return;}if (stopRecognizer) {camera.stopPreview();} else {camera.startPreview();}});adjustSurface(preview, ocrArea);}private void adjustSurface(SurfaceView cameraPreview, OCRDrawView ocrArea) {FrameLayout.LayoutParams cameraPreviewParams (FrameLayout.LayoutParams) cameraPreview.getLayoutParams();cameraPreviewParams.width WIDTH;cameraPreviewParams.height HEIGHT;ViewGroup.LayoutParams ocrAreaParams ocrArea.getLayoutParams();ocrAreaParams.width WIDTH;ocrAreaParams.height HEIGHT;}Overridepublic void onRequestPermissionsResult(int requestCode, NonNull String[] permissions, NonNull int[] grantResults) {super.onRequestPermissionsResult(requestCode, permissions, grantResults);if (requestCode REQUEST_CAMERA grantResults.length 0) {if (grantResults[0] PackageManager.PERMISSION_GRANTED) {preview.getHolder().addCallback(this);surfaceCreated(preview.getHolder());camera.setPreviewCallback(this);camera.startPreview();} else {finish();}}}Overridepublic void onPreviewFrame(byte[] data, Camera camera) {if (isRecognizering || stopRecognizer) {return;}Bitmap bitmap convertToBitmap(camera, data);isRecognizering true;recognizer.process(bitmap, ORIENTATION).addOnSuccessListener(text - {parseOCRResult(text);}).addOnFailureListener(exception - {Toast.makeText(this, Failure, Toast.LENGTH_SHORT).show();isRecognizering false;}).addOnCompleteListener(task - {isRecognizering false;}).addOnCanceledListener(() - {Toast.makeText(this, Canceled, Toast.LENGTH_SHORT).show();isRecognizering false;});}private void parseOCRResult(Text text) {// 所有识别到的内容下同String textContent text.getText();if (textContent null || textContent.trim().length() 0) {return;}ocrArea.clear();// 块段落for (Text.TextBlock textBlock : text.getTextBlocks()) {// 一行文本for (Text.Line line : textBlock.getLines()) {drawResult(line);// 元素单词对汉字来说需要开头 (分隔符)中间分隔符 结尾之类比较强烈的分隔符去分隔for (Text.Element element : line.getElements()) {// symbol字符字母字for (Text.Symbol symbol : element.getSymbols()) {symbol.getText();}}}}}private void drawResult(Text.Line line) {// line的旋转角度以度为单位顺时针为正范围为[-180, 180]float angle line.getAngle() ORIENTATION;// 检测到的文本的轴对齐边界矩形Rect boundingBox line.getBoundingBox();// 从左上角开始顺时针方向的四个角点。不带旋转角度如果设置过旋转角度camera.setDisplayOrientation需要进行旋转Point[] cornerPoints line.getCornerPoints();// 置信度float confidence line.getConfidence();// 获取文本中的主要语言如果有的话String recognizedLanguage line.getRecognizedLanguage();// 置信度太低的过滤掉if (confidence 0.3f) {return;}for (Point cornerPoint : cornerPoints) {float[] floats {cornerPoint.x, cornerPoint.y};matrix.mapPoints(floats);cornerPoint.x (int) floats[0] (WIDTH 1);cornerPoint.y (int) floats[1] (HEIGHT 1);}ocrArea.add(cornerPoints, line.getText());ocrArea.postInvalidate();}/*** Convert camera data into bitmap data.*/private Bitmap convertToBitmap(Camera camera, byte[] data) {int width camera.getParameters().getPreviewSize().width;int height camera.getParameters().getPreviewSize().height;YuvImage yuv new YuvImage(data, ImageFormat.NV21, width, height, null);ByteArrayOutputStream stream new ByteArrayOutputStream();yuv.compressToJpeg(new Rect(0, 0, width, height), 100, stream);return BitmapFactory.decodeByteArray(stream.toByteArray(), 0, stream.toByteArray().length);}Overrideprotected void onResume() {super.onResume();}Overrideprotected void onRestart() {super.onRestart();}Overrideprotected void onDestroy() {super.onDestroy();if (recognizer ! null) {recognizer.close();}}Overridepublic void surfaceCreated(NonNull SurfaceHolder holder) {try {camera Camera.open(Camera.CameraInfo.CAMERA_FACING_BACK);parameters camera.getParameters();// 旋转了90度所以height、width互换parameters.setPictureSize(HEIGHT, WIDTH);parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);parameters.setPictureFormat(ImageFormat.NV21);camera.setPreviewDisplay(holder);camera.setDisplayOrientation(ORIENTATION);camera.setParameters(parameters);} catch (Exception exception) {Log.i(TAG, exception.getMessage());}}Overridepublic void surfaceChanged(NonNull SurfaceHolder holder, int format, int width, int height) {if (camera ! null) {camera.stopPreview();camera.setPreviewCallback(null);camera.startPreview();camera.setPreviewCallback(this);ocrArea.clear();stopRecognizer true;ocrSwitch.performClick();}}Overridepublic void surfaceDestroyed(NonNull SurfaceHolder holder) {if (camera ! null) {camera.stopPreview();camera.setPreviewCallback(null);camera.release();}}
}参考文章
文字识别 v2
