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    Android开发轻松实现基于Tesseract的Android OCR应用程序

    时间:2019-02-28 22:58 来源:互联网 作者:源码搜藏 浏览:收藏 挑错 推荐 打印

    介绍 此应用程序使用Tesseract 3的Tesseract OCR引擎,该引擎通过识别字符模式( https://github.com/tesseract-ocr/tesseract )来工作。 Tesseract具有unicode(UTF-8)支持,可以开箱即用识别100多种语言。 背景 我尝试了Google文本识别API- https://deve

    介绍

    此应用程序使用Tesseract 3的Tesseract OCR引擎,该引擎通过识别字符模式(https://github.com/tesseract-ocr/tesseract)来工作。Tesseract具有unicode(UTF-8)支持,可以“开箱即用”识别100多种语言。

    背景

    我尝试了Google文本识别API- https://developers.google.com/vision/android/text-overview,但它不适合我,所以我找到了这个惊人的引擎。

    使用代码

    开始吧!在Android studio中创建一个新项目(我使用的是3.2.1版),或者您可以下载源文件并选择:File-New-Import项目。

    Android开发轻松实现基于Tesseract的Android OCR应用程序

    添加到build.gradle应用程序级别:

    implementation 'com.jakewharton:butterknife:8.8.1'
    annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'
    
    implementation 'com.rmtheis:tess-two:9.0.0'

    我使用Butterknife库,它非常有用,主库是 - ' tess-two:9.0.0'' - 它包含一个Android的Tesseract工具(tesseract-android-tools的分支,它增加了一些额外的功能。此外,我们需要相机和写入权限,因此将其添加到AndroidManifest.xml

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-feature android:name="android.hardware.camera" />
    <uses-permission android:name="android.permission.CAMERA" />

    做一个简单的布局文件ButtonTextView并且ImageView

    <?xml version="1.0" encoding="utf-8"?>
    <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    
        xmlns:tools="http://schemas.android.com/tools"
    
        android:layout_width="match_parent"
    
        android:layout_height="wrap_content"
    
        android:fillViewport="true"
    
        tools:context=".MainActivity">
    
        <LinearLayout
    
            android:layout_width="match_parent"
    
            android:layout_height="wrap_content"
    
            android:orientation="vertical">
    
            <LinearLayout
    
                android:layout_width="match_parent"
    
                android:layout_height="wrap_content"
    
                android:orientation="vertical">
    
                <Button
    
                    android:id="@+id/scan_button"
    
                    android:layout_width="wrap_content"
    
                    android:layout_height="wrap_content"
    
                    android:layout_gravity="center"
    
                    android:text="scan" />
            </LinearLayout>
    
            <LinearLayout
    
                android:layout_width="match_parent"
    
                android:layout_height="wrap_content"
    
                android:layout_margin="4dp"
    
                android:orientation="horizontal">
    
                <TextView
    
                    android:id="@+id/ocr_text"
    
                    android:layout_width="match_parent"
    
                    android:layout_height="wrap_content"
    
                    android:layout_gravity="fill"
    
                    android:text=" text">
    
                </TextView>
    
            </LinearLayout>
    
            <LinearLayout
    
                android:layout_width="match_parent"
    
                android:layout_height="wrap_content"
    
                android:orientation="vertical">
    
                <ImageView
    
                    android:id="@+id/ocr_image"
    
                    android:layout_width="match_parent"
    
                    android:layout_height="wrap_content" />
    
            </LinearLayout>
    
        </LinearLayout>
    </ScrollView>

    我们得到这样的东西:

    Android开发轻松实现基于Tesseract的Android OCR应用程序

    编写一些代码来检查权限:

    void checkPermissions() {
        if (!hasPermissions(context, PERMISSIONS)) {
            requestPermissions(PERMISSIONS,
                    PERMISSION_ALL);
            flagPermissions = false;
        }
        flagPermissions = true;
    }
    
    public static boolean hasPermissions(Context context, String... permissions) {
        if (context != null && permissions != null) {
            for (String permission : permissions) {
                if (ActivityCompat.checkSelfPermission(context, permission) 
                                           != PackageManager.PERMISSION_GRANTED) {
                    return false;
                }
            }
        }
        return true;
    }

    和代码来创建一个文件:

    public File createImageFile() throws IOException {
        // Create an image file name
        String timeStamp = new SimpleDateFormat("MMdd_HHmmss").format(new Date());
        String imageFileName = "JPEG_" + timeStamp + "_";
        File storageDir = context.getExternalFilesDir(Environment.DIRECTORY_PICTURES);
        File image = File.createTempFile(
                imageFileName,  /* prefix */
                ".jpg",         /* suffix */
                storageDir      /* directory */
        );
        // Save a file: path for use with ACTION_VIEW intents
        mCurrentPhotoPath = image.getAbsolutePath();
        return image;
    }

    首先,我们需要写onClickScanButton函数,它:

    @OnClick(R.id.scan_button)
    void onClickScanButton() {
        // check permissions
        if (!flagPermissions) {
            checkPermissions();
            return;
        }
        //prepare intent
        Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    
        if (takePictureIntent.resolveActivity(context.getPackageManager()) != null) {
            File photoFile = null;
            try {
                photoFile = createImageFile();
            } catch (IOException ex) {
                Toast.makeText(context, errorFileCreate, Toast.LENGTH_SHORT).show();
                Log.i("File error", ex.toString());
            }
            // Continue only if the File was successfully created
            if (photoFile != null) {
                oldPhotoURI = photoURI1;
                photoURI1 = Uri.fromFile(photoFile);
                takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, photoURI1);
                startActivityForResult(takePictureIntent, REQUEST_IMAGE1_CAPTURE);
            }
        }
    }

    我们可以在这里查看结果:

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
    
        switch (requestCode) {
            case REQUEST_IMAGE1_CAPTURE: {
                if (resultCode == RESULT_OK) {
                    Bitmap bmp = null;
                    try {
                        InputStream is = context.getContentResolver().openInputStream(photoURI1);
                        BitmapFactory.Options options = new BitmapFactory.Options();
                        bmp = BitmapFactory.decodeStream(is, null, options);
    
                    } catch (Exception ex) {
                        Log.i(getClass().getSimpleName(), ex.getMessage());
                        Toast.makeText(context, errorConvert, Toast.LENGTH_SHORT).show();
                    }
    
                    firstImage.setImageBitmap(bmp);
                    doOCR(bmp);
    
                    OutputStream os;
                    try {
                        os = new FileOutputStream(photoURI1.getPath());
                        if (bmp != null) {
                            bmp.compress(Bitmap.CompressFormat.JPEG, 100, os);
                        }
                        os.flush();
                        os.close();
                    } catch (Exception ex) {
                        Log.e(getClass().getSimpleName(), ex.getMessage());
                        Toast.makeText(context, errorFileCreate, Toast.LENGTH_SHORT).show();
                    }
    
                } else {
                    {
                        photoURI1 = oldPhotoURI;
                        firstImage.setImageURI(photoURI1);
                    }
                }
            }
        }
    }

    接下来将Tesseract集成到我们的项目中,进行额外的课程:TesseractOCR

    Assets文件夹中为英语语言添加了训练有素的数据文件“ eng.traineddata ” ,因此我们需要将其从APK复制到内部存储器文件目录,然后启动Tesseract系统:mTess.init(dstInitPathDir, language)

    public class TesseractOCR {
    
        private final TessBaseAPI mTess;
    
        public TesseractOCR(Context context, String language) {
            mTess = new TessBaseAPI();
            boolean fileExistFlag = false;
    
            AssetManager assetManager = context.getAssets();
    
            String dstPathDir = "/tesseract/tessdata/";
    
            String srcFile = "eng.traineddata";
            InputStream inFile = null;
    
            dstPathDir = context.getFilesDir() + dstPathDir;
            String dstInitPathDir = context.getFilesDir() + "/tesseract";
            String dstPathFile = dstPathDir + srcFile;
            FileOutputStream outFile = null;
    
            try {
                inFile = assetManager.open(srcFile);
    
                File f = new File(dstPathDir);
    
                if (!f.exists()) {
                    if (!f.mkdirs()) {
                        Toast.makeText(context, srcFile + " can't be created.", Toast.LENGTH_SHORT).show();
                    }
                    outFile = new FileOutputStream(new File(dstPathFile));
                } else {
                    fileExistFlag = true;
                }
    
            } catch (Exception ex) {
                Log.e(TAG, ex.getMessage());
    
            } finally {
    
                if (fileExistFlag) {
                    try {
                        if (inFile != null) inFile.close();
                        mTess.init(dstInitPathDir, language);
                        return;
    
                    } catch (Exception ex) {
                        Log.e(TAG, ex.getMessage());
                    }
                }
    
                if (inFile != null && outFile != null) {
                    try {
                        //copy file
                        byte[] buf = new byte[1024];
                        int len;
                        while ((len = inFile.read(buf)) != -1) {
                            outFile.write(buf, 0, len);
                        }
                        inFile.close();
                        outFile.close();
                        mTess.init(dstInitPathDir, language);
                    } catch (Exception ex) {
                        Log.e(TAG, ex.getMessage());
                    }
                } else {
                    Toast.makeText(context, srcFile + " can't be read.", Toast.LENGTH_SHORT).show();
                }
            }
        }
    
        public String getOCRResult(Bitmap bitmap) {
            mTess.setImage(bitmap);
            return mTess.getUTF8Text();
        }
    
        public void onDestroy() {
            if (mTess != null) mTess.end();
        }
    }

    OCR代码很简单 - 我们需要将图像(位图BMP)传递给该对象并获得结果:

    public String getOCRResult(Bitmap bitmap) { 
    mTess.setImage(bitmap); 
    return mTess.getUTF8Text(); }

    OCR可能需要很长时间,因此我们需要在另一个中进行Thread

    private void doOCR(final Bitmap bitmap) {
        if (mProgressDialog == null) {
            mProgressDialog = ProgressDialog.show(this, "Processing",
                    "Doing OCR...", true);
        } else {
            mProgressDialog.show();
        }
        new Thread(new Runnable() {
            public void run() {
                final String srcText = mTessOCR.getOCRResult(bitmap);
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
    
                        if (srcText != null && !srcText.equals("")) {
                            ocrText.setText(srcText);
                        }
                        mProgressDialog.dismiss();
                    }
                });
            }
        }).start();
    }

    源图像如下:

    Android开发轻松实现基于Tesseract的Android OCR应用程序

    OCR的结果如下:

    Android开发轻松实现基于Tesseract的Android OCR应用程序

    Android开发轻松实现基于Tesseract的Android OCR应用程序转载http://www.codesocang.com/appboke/39582.html
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