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HarmonyOS NEXT Card Document Recognition Technology Deep Dive and Implementation

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1. Technical Background

As Huawei's next-generation operating system, HarmonyOS NEXT provides powerful AI capabilities. Card document recognition is a common functional requirement in mobile applications, such as quick entry of ID cards and bank card information. This article will explain how to leverage HarmonyOS NEXT's AI capabilities to achieve efficient card document recognition.

2. Technical Implementation

1. Preparation

First, declare necessary permissions in module.json5:

{
  "module": {
    "requestPermissions": [
      {
        "name": "ohos.permission.CAMERA"
      },
      {
        "name": "ohos.permission.READ_MEDIA"
      }
    ]
  }
}
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2. Core Code Implementation 

import { BusinessError } from '@ohos.base';
import { cardRecognition } from '@ohos.ai.cardRecognition';
import { image } from '@ohos.multimedia.image';
import { camera } from '@ohos.multimedia.camera';

// 1. Initialize card recognition engine
async function initCardRecognizer(): Promise<cardRecognition.CardRecognition> {
  try {
    let cardRecognizer = await cardRecognition.createCardRecognition();
    console.info('Card recognition engine initialized successfully');
    return cardRecognizer;
  } catch (error) {
    console.error(`Initialization failed, error code: ${(error as BusinessError).code}`);
    throw error;
  }
}

// 2. Configure recognition parameters
function setRecognitionConfig(cardRecognizer: cardRecognition.CardRecognition) {
  const config: cardRecognition.RecognitionConfig = {
    language: 'zh', // Recognition language
    type: cardRecognition.CardType.ID_CARD_FRONT, // Front side of ID card
    resultMode: cardRecognition.ResultMode.TEXT // Return text results
  };
  cardRecognizer.setConfig(config);
}

// 3. Execute card recognition
async function recognizeCard(cardRecognizer: cardRecognition.CardRecognition, 
                           imageSource: image.ImageSource): Promise<string> {
  try {
    const result = await cardRecognizer.recognize(imageSource);
    console.info('Recognition result: ' + JSON.stringify(result));
    return result.text;
  } catch (error) {
    console.error(`Recognition failed, error code: ${(error as BusinessError).code}`);
    throw error;
  }
}

// 4. Release resources
function releaseCardRecognizer(cardRecognizer: cardRecognition.CardRecognition) {
  cardRecognizer.release();
  console.info('Card recognition engine released');
}
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3. Key Technical Points Analysis

  1. Multi-framework Collaboration: HarmonyOS NEXT card recognition integrates AI framework, multimedia framework and security framework to ensure efficient and secure recognition.

  2. Intelligent Cropping Technology: The system automatically detects document edges and performs perspective transformation correction to improve OCR recognition accuracy.

  3. Dynamic Resource Loading: Recognition models are loaded on demand to reduce memory usage.

  4. Multi-thread Optimization: The recognition process runs in a separate thread to avoid blocking the UI thread.

4. Best Practice Recommendations

  1. Preprocessing Optimization:
  • Ensure image clarity (recommended resolution not lower than 1280×720)
  • Appropriate contrast enhancement can improve recognition rate
  1. Performance Optimization: 
   // Set appropriate image decoding parameters
   const decodeOptions: image.DecodingOptions = {
     desiredSize: { width: 800, height: 600 }, // Appropriately reduce resolution
     desiredPixelFormat: image.PixelFormat.RGBA_8888
   };
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  1. Enhanced Error Handling: 
   // Add retry mechanism
   async function recognizeWithRetry(imageSource: image.ImageSource, retryCount = 3) {
     let lastError;
     for (let i = 0; i < retryCount; i++) {
       try {
         const recognizer = await initCardRecognizer();
         setRecognitionConfig(recognizer);
         return await recognizeCard(recognizer, imageSource);
       } catch (error) {
         lastError = error;
         await new Promise(resolve => setTimeout(resolve, 500)); // Delay retry
       }
     }
     throw lastError;
   }
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5. Conclusion

The card recognition capability provided by HarmonyOS NEXT achieves efficient and accurate recognition results through deeply optimized AI algorithms and system-level integration. Developers only need to focus on business logic without delving into underlying details to quickly build high-quality card recognition features. As HarmonyOS AI capabilities continue to improve, card recognition accuracy and speed will be further enhanced in the future.

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