/**
 * Get a CSS custom property value from an element's computed styles
 *
 * This is specifically designed for Chart.js canvas rendering, where CSS variables
 * must be resolved to actual color values before being passed to the canvas context.
 * Unlike DOM elements, canvas doesn't inherit CSS properties, so we must read
 * computed values from the host element.
 *
 * @param element - The HTML element to read CSS variables from (typically the chart component)
 * @param name - The CSS custom property name (e.g., '--base-blue-500')
 * @returns The resolved CSS value as a string (trimmed)
 *
 * @example
 * const color = getCssVariableValue(this, '--element-neutral-color');
 * // Returns: "rgb(83, 83, 83)"
 */
export declare function getCssVariableValue(element: HTMLElement, name: string): string;
/**
 * Get chart colors: use custom colors if provided, otherwise fall back to CSS theme variables
 * @param element - The HTML element to read CSS variables from
 * @param customColors - User-provided color array (hex, rgb, etc.)
 * @param defaultColorVars - CSS custom property names to use as fallback (e.g., ['--base-blue-500', '--base-blue-400'])
 * @returns Array of resolved color strings
 */
export declare function getChartColorsOrDefault(element: HTMLElement, customColors: string[], defaultColorVars: readonly string[]): string[];
/**
 * Apply alpha transparency to a color string.
 * Supports hex (#RGB/#RRGGBB), rgb(), rgba(), and CSS variable references.
 *
 * @param element - Host element for CSS variable resolution
 * @param color - Color string (hex, rgb, rgba, CSS var, or CSS var reference)
 * @param alpha - Alpha value (0-1)
 * @returns Color string with applied alpha as rgba()
 *
 * @example
 * // Hex color
 * applyAlphaToColor(this, '#3498db', 0.5) // returns 'rgba(52, 152, 219, 0.5)'
 *
 * // CSS variable
 * applyAlphaToColor(this, '--base-blue-500', 0.3) // returns 'rgba(r, g, b, 0.3)'
 *
 * // RGB color
 * applyAlphaToColor(this, 'rgb(52, 152, 219)', 0.7) // returns 'rgba(52, 152, 219, 0.7)'
 */
export declare function applyAlphaToColor(element: HTMLElement, color: string | CanvasGradient | CanvasPattern | undefined, alpha?: number): string;
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