/** Source extensions for which the build pipeline emits optimized variants. */
export declare const OPTIMIZABLE_IMAGE_SOURCE_EXTENSIONS: readonly ["jpg", "jpeg", "png", "webp", "avif"];
export declare function isOptimizableImageSourceExtension(extension: string): boolean;
/** Extract a build-supported extension using the same basename rule as path.extname. */
export declare function getOptimizableImageSourceExtension(path: string): string | null;
export declare function isValidImageVariantWidth(value: unknown): value is number;
/**
 * Resolve the no-enlargement width matrix emitted by image optimization.
 * Configured widths above the intrinsic source width are omitted, and the
 * intrinsic width is always included exactly once.
 */
export declare function resolveImageVariantWidths(sourceWidth: number, configuredWidths?: readonly number[]): number[];
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