Fixed Square Brush, Improve Brush Hardness and Smoothing Precision (#4519)

* Fixed square brush with hardness <1; improved the effect of hardness, improved the effect of smoothing precision

* Improved square hardness and code quality with performance optimizations

* Fix brush rendering anti-aliasing and optimized square brushes using texture caching

* Switched to QuickLRU for brush cache

* Cleaned up exports from testing

* Removed SOFT_BRUSH_STEPS unused variable

src/utils/colorUtil.ts

@@ -59,6 +59,59 @@ export function hexToRgb(hex: string): RGB {
   return { r, g, b }
 }
 
+export function parseToRgb(color: string): RGB {
+  const format = identifyColorFormat(color)
+  if (!format) return { r: 0, g: 0, b: 0 }
+
+  const hsla = parseToHSLA(color, format)
+  if (!isHSLA(hsla)) return { r: 0, g: 0, b: 0 }
+
+  // Convert HSL to RGB
+  const h = hsla.h / 360
+  const s = hsla.s / 100
+  const l = hsla.l / 100
+
+  const c = (1 - Math.abs(2 * l - 1)) * s
+  const x = c * (1 - Math.abs(((h * 6) % 2) - 1))
+  const m = l - c / 2
+
+  let r = 0,
+    g = 0,
+    b = 0
+
+  if (h < 1 / 6) {
+    r = c
+    g = x
+    b = 0
+  } else if (h < 2 / 6) {
+    r = x
+    g = c
+    b = 0
+  } else if (h < 3 / 6) {
+    r = 0
+    g = c
+    b = x
+  } else if (h < 4 / 6) {
+    r = 0
+    g = x
+    b = c
+  } else if (h < 5 / 6) {
+    r = x
+    g = 0
+    b = c
+  } else {
+    r = c
+    g = 0
+    b = x
+  }
+
+  return {
+    r: Math.round((r + m) * 255),
+    g: Math.round((g + m) * 255),
+    b: Math.round((b + m) * 255)
+  }
+}
+
 const identifyColorFormat = (color: string): ColorFormat | null => {
   if (!color) return null
   if (color.startsWith('#') && (color.length === 4 || color.length === 7))