/**
 * Applies alpha (opacity) to a color string.
 * This is useful as an alternative to using ctx.globalAlpha, which affects all drawing operations.
 * Instead, you can apply opacity directly to specific colors.
 *
 * @param color - Color in any valid CSS format (hex, rgb, rgba, hsl, hsla, named colors)
 * @param alpha - Alpha value between 0 (fully transparent) and 1 (fully opaque)
 * @returns Color string in rgba format with applied alpha
 *
 * @example
 * applyAlpha('#ff0000', 0.5) // returns 'rgba(255, 0, 0, 0.5)'
 * applyAlpha('rgb(255, 0, 0)', 0.5) // returns 'rgba(255, 0, 0, 0.5)'
 * applyAlpha('rgba(255, 0, 0, 0.8)', 0.5) // returns 'rgba(255, 0, 0, 0.4)' - multiplies existing alpha
 * applyAlpha('red', 0.5) // returns 'rgba(255, 0, 0, 0.5)'
 */
export declare function applyAlpha(color: string, alpha: number): string;
/**
 * Clears the color cache to free up memory.
 * Use this if you've processed a large number of unique colors and want to reclaim memory.
 */
export declare function clearColorCache(): void;