src/adapters/crnn.ts

/**
 * CRNN/CTC Output Format Adapter
 * 
 * Format:
 * images/
 *   img_000000.png
 *   img_000001.png
 *   ...
 * labels.txt (filename<TAB>label)
 */

import { mkdir, writeFile } from 'fs/promises';
import { join } from 'path';

export interface CRNNOptions {
    delimiter?: string;
    includeExtension?: boolean;
}

export interface CRNNOutput {
    imageDir: string;
    labelsFile: string;
    count: number;
}

/**
 * CRNN Adapter class
 */
export class CRNNAdapter {
    private outputDir: string;
    private options: CRNNOptions;
    private labels: string[] = [];

    constructor(outputDir: string, options: CRNNOptions = {}) {
        this.outputDir = join(outputDir, 'crnn');
        this.options = {
            delimiter: options.delimiter || '\t',
            includeExtension: options.includeExtension ?? true,
        };
    }

    /**
     * Initialize output directories
     */
    async init(): Promise<void> {
        await mkdir(join(this.outputDir, 'images'), { recursive: true });
        this.labels = [];
    }

    /**
     * Add a sample
     */
    addSample(imageFilename: string, text: string): void {
        const filename = this.options.includeExtension
            ? imageFilename
            : imageFilename.replace(/\.[^.]+$/, '');

        this.labels.push(`${filename}${this.options.delimiter}${text}`);
    }

    /**
     * Get image output path for a sample
     */
    getImagePath(index: number, prefix: string = 'img'): string {
        const filename = `${prefix}_${String(index).padStart(6, '0')}.png`;
        return join(this.outputDir, 'images', filename);
    }

    /**
     * Finalize and write labels file
     */
    async finalize(): Promise<CRNNOutput> {
        const labelsPath = join(this.outputDir, 'labels.txt');
        await writeFile(labelsPath, this.labels.join('\n'), 'utf-8');

        return {
            imageDir: join(this.outputDir, 'images'),
            labelsFile: labelsPath,
            count: this.labels.length,
        };
    }

    /**
     * Get statistics
     */
    getStats(): { count: number } {
        return { count: this.labels.length };
    }
}

/**
 * Create CRNN adapter
 */
export function createCRNNAdapter(outputDir: string, options?: CRNNOptions): CRNNAdapter {
    return new CRNNAdapter(outputDir, options);
}