From 64cfeb3169311472afc7881548580e870ea231c1 Mon Sep 17 00:00:00 2001
From: LuciNyan <22126563+LuciNyan@users.noreply.github.com>
Date: Wed, 4 Sep 2024 14:47:44 +0800
Subject: [PATCH] perf: enhance glow rendering speed (#43)

---
 packages/pixel-profile/src/shaders/glow.ts | 62 +++++++---------------
 1 file changed, 20 insertions(+), 42 deletions(-)

diff --git a/packages/pixel-profile/src/shaders/glow.ts b/packages/pixel-profile/src/shaders/glow.ts
index 037a2dc..eb434df 100644
--- a/packages/pixel-profile/src/shaders/glow.ts
+++ b/packages/pixel-profile/src/shaders/glow.ts
@@ -1,10 +1,11 @@
 import { coordsToIndex, render, RGBA } from '../renderer'
-import { add2, Vec2 } from '../utils'
-import { add3, divide3, dot3, mix3, Vec3 } from '../utils/math'
+import { Vec2 } from '../utils'
+import { add3, divide3, mix3, Vec3 } from '../utils/math'
 
 const radius = 5
 const intensity = 0.7
 const threshold = 0.8
+const radiusSquared = radius * radius * 2
 
 export function glow(source: Buffer, width: number, height: number): Buffer {
   const memo: { result: boolean; sampledColor: RGBA; luminance: number }[] = new Array(width * height)
@@ -21,57 +22,34 @@ export function glow(source: Buffer, width: number, height: number): Buffer {
 
       for (let i = -radius; i <= radius; i++) {
         for (let j = -radius; j <= radius; j++) {
-          const _uv: Vec2 = add2(uv, [i, j])
+          const _uv: Vec2 = [uv[0] + i, uv[1] + j]
           const key = coordsToIndex(_uv[0], _uv[1], width)
-          if (memo[key]) {
-            if (memo[key].result) {
-              const sampledColor = memo[key].sampledColor
-              const luminance = memo[key].luminance
 
-              const dist = length2([i, j])
-              const weight = Math.pow(Math.exp((-dist * dist) / (2 * radius * radius)), 3)
-              glowColor = add3(
-                glowColor,
-                mix3(originalColor, sampledColor, weight * intensity * Math.pow(luminance, 5))
-              )
-
-              n++
+          if (!memo[key]) {
+            const sampledColor = texture2D(_uv)
+            const luminance = (sampledColor[0] * 0.2126 + sampledColor[1] * 0.7152 + sampledColor[2] * 0.0722) / 255
+            memo[key] = {
+              result: luminance > threshold,
+              sampledColor,
+              luminance
             }
-            continue
           }
-          memo[key] = {} as any
 
-          const sampledColor = texture2D(_uv)
-          const luminance = dot3(sampledColor, [0.2126, 0.7152, 0.0722]) / 255
-          if (luminance > threshold) {
-            const dist = length2([i, j])
-            const weight = Math.pow(Math.exp((-dist * dist) / (2 * radius * radius)), 3)
-            glowColor = add3(glowColor, mix3(originalColor, sampledColor, weight * intensity * Math.pow(luminance, 5)))
+          if (memo[key].result) {
+            const { sampledColor, luminance } = memo[key]
+            const distSquared = i * i + j * j
+            const weight = Math.exp(-distSquared / radiusSquared) ** 3
+            const factor = weight * intensity * luminance ** 5
+            glowColor = add3(glowColor, mix3(originalColor, sampledColor, factor))
             n++
-
-            memo[key].result = true
-            memo[key].sampledColor = sampledColor
-            memo[key].luminance = luminance
-          } else {
-            memo[key].result = false
           }
         }
       }
 
-      if (n === 0) {
-        return originalColor
-      }
-
-      glowColor = divide3(glowColor, n)
+      if (n === 0) return originalColor
 
-      return [glowColor[0], glowColor[1], glowColor[2], 255]
+      return [...divide3(glowColor, n), 255]
     },
-    {
-      textureFilter: 'NEAREST'
-    }
+    { textureFilter: 'NEAREST' }
   )
 }
-
-function length2(v: Vec2): number {
-  return Math.sqrt(v[0] * v[0] + v[1] * v[1])
-}