/**
 * Image Quality Assessment for Document Capture
 * Client-side quality checks before sending to backend
 */
export interface QualityMetrics {
    sharpness: number;
    contrast: number;
    brightness: number;
    isBlurry: boolean;
    hasGlare: boolean;
    overallScore: number;
}
export interface QualityFeedback {
    isValid: boolean;
    message: string;
    recommendations: string[];
    quality: QualityMetrics;
}
/**
 * Calculate image sharpness using Laplacian variance
 * Higher values = sharper image
 */
export declare function calculateSharpness(imageData: ImageData): number;
/**
 * Detect glare (overexposed areas)
 */
export declare function detectGlare(imageData: ImageData, threshold?: number): number;
/**
 * Calculate contrast (standard deviation)
 */
export declare function calculateContrast(imageData: ImageData): number;
/**
 * Calculate brightness (mean pixel value)
 */
export declare function calculateBrightness(imageData: ImageData): number;
/**
 * Full quality assessment.
 *
 * Threshold note: these cutoffs (sharpness<80, glare>15%, brightness
 * outside 50-200, contrast<30) are not calibrated against a specific input
 * resolution — Laplacian-variance sharpness in particular scales with image
 * size, so scoring a full-resolution capture vs. a downscaled copy can
 * shift the result. Caller (DocumentCapture._checkPhotoQuality) downscales
 * to a fixed 640px before calling this, so keep that pairing consistent —
 * if the downscale size changes, these thresholds should be re-checked
 * against real captures at the new size. This function is used as an
 * advisory-only nudge (never blocks submission), so a threshold that's
 * somewhat off costs an occasional wrong nudge, not a broken flow.
 */
export declare function assessQuality(imageData: ImageData): QualityFeedback;
/**
 * Get quality color for UI feedback
 */
export declare function getQualityColor(score: number): string;
/**
 * Get quality message for display
 */
export declare function getQualityMessage(score: number): string;
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