feat(image-pipeline): expand webgl backend step coverage

lib/image-pipeline/backend/webgl/shaders/light-adjust.frag.glsl

@@ -0,0 +1,52 @@
+precision mediump float;
+
+varying vec2 vUv;
+uniform sampler2D uSource;
+uniform float uExposureFactor;
+uniform float uContrastFactor;
+uniform float uBrightnessShift;
+uniform float uHighlights;
+uniform float uShadows;
+uniform float uWhites;
+uniform float uBlacks;
+uniform float uVignetteAmount;
+uniform float uVignetteSize;
+uniform float uVignetteRoundness;
+
+float toByte(float value) {
+  return clamp(floor(value + 0.5), 0.0, 255.0);
+}
+
+void main() {
+  vec4 color = texture2D(uSource, vUv);
+  vec3 rgb = color.rgb * 255.0;
+
+  rgb *= uExposureFactor;
+  rgb = (rgb - 128.0) * uContrastFactor + 128.0 + uBrightnessShift;
+
+  float luma = dot(rgb, vec3(0.2126, 0.7152, 0.0722));
+  float highlightsBoost = (luma / 255.0) * uHighlights * 40.0;
+  float shadowsBoost = ((255.0 - luma) / 255.0) * uShadows * 40.0;
+  float whitesBoost = (luma / 255.0) * uWhites * 35.0;
+  float blacksBoost = ((255.0 - luma) / 255.0) * uBlacks * 35.0;
+  float totalBoost = highlightsBoost + shadowsBoost + whitesBoost + blacksBoost;
+  rgb = vec3(
+    toByte(rgb.r + totalBoost),
+    toByte(rgb.g + totalBoost),
+    toByte(rgb.b + totalBoost)
+  );
+
+  if (uVignetteAmount > 0.0) {
+    vec2 centeredUv = (vUv - vec2(0.5)) / vec2(0.5);
+    float radialDistance = length(centeredUv);
+    float softEdge = pow(1.0 - clamp(radialDistance, 0.0, 1.0), 1.0 + uVignetteRoundness);
+    float strength = 1.0 - uVignetteAmount * (1.0 - softEdge) * (1.5 - uVignetteSize);
+    rgb = vec3(
+      toByte(rgb.r * strength),
+      toByte(rgb.g * strength),
+      toByte(rgb.b * strength)
+    );
+  }
+
+  gl_FragColor = vec4(clamp(rgb / 255.0, 0.0, 1.0), color.a);
+}