/**
 * Image preprocessing for PaddleOCR PP-OCRv6 small recognition.
 *
 * Matches PaddleOCR's OCRReisizeNormImg (paddlex/inference/models/text_recognition/processors.py):
 *   - Resize to height 48 preserving aspect ratio; width = int(48 * max(320/48, w/h))
 *   - Cap width at maxImgW (3200)
 *   - Normalize: (x/255 - 0.5) / 0.5  → range [-1, 1]
 *   - Pad remaining width with ZEROS (black, which is -1.0 after normalization)
 *   - Channel order: BGR (PaddleOCR default), NCHW [1, 3, 48, W]
 */
export interface PreprocessedImage {
    shape: [1, 3, 48, number];
    data: Float32Array;
}
export declare function preprocessImage(src: HTMLCanvasElement | HTMLImageElement | ImageData | Uint8ClampedArray, maxWidth?: number): PreprocessedImage;
/** Variant that orders channels RGB (used by PP-OCRv6 small_rec). */
export declare function preprocessImageRGB(src: HTMLCanvasElement | HTMLImageElement | ImageData | Uint8ClampedArray, maxWidth?: number): PreprocessedImage;
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