Add a magnifying glass example (#2419)

* Add a magnifying glass example

* lint fix

---------

Co-authored-by: William Candillon <wcandillon@gmail.com>

example/src/App.tsx

@@ -14,6 +14,7 @@ import {
   Aurora,
   Breathe,
   Filters,
+  MagnifyingGlass,
   Gooey,
   GraphsScreen,
   Hue,
@@ -44,6 +45,7 @@ const linking: LinkingOptions<StackParamList> = {
       API: "api",
       Breathe: "breathe",
       Filters: "filters",
+      MagnifyingGlass: "magnifying-glass",
       Gooey: "gooey",
       Hue: "hue",
       Matrix: "matrix",
@@ -127,6 +129,7 @@ const App = () => {
             <Stack.Screen name="API" component={API} />
             <Stack.Screen name="Breathe" component={Breathe} />
             <Stack.Screen name="Filters" component={Filters} />
+            <Stack.Screen name="MagnifyingGlass" component={MagnifyingGlass} />
             <Stack.Screen name="Gooey" component={Gooey} />
             <Stack.Screen name="Hue" component={Hue} />
             <Stack.Screen

example/src/Examples/Examples.test.tsx

@@ -16,6 +16,7 @@ import { Matrix } from "./Matrix";
 import { Hue } from "./Hue";
 import { Glassmorphism } from "./Glassmorphism";
 import { Filters } from "./Filters";
+import { MagnifyingGlass } from "./MagnifyingGlass";
 
 it("should render the Breathe example correctly", () => {
   render(<Breathe />);
@@ -69,4 +70,8 @@ it("should render the Filter example correctly", () => {
   render(<Filters />);
 });
 
+it("should render the MagnifyingGlass example correctly", () => {
+  render(<MagnifyingGlass />);
+});
+
 afterEach(cleanup);

example/src/Examples/MagnifyingGlass/MagnifyingGlass.tsx

@@ -0,0 +1,193 @@
+import React, { useState } from "react";
+import type { LayoutChangeEvent } from "react-native";
+import { Button, PixelRatio, StyleSheet, Text, View } from "react-native";
+import {
+  Canvas,
+  Group,
+  Image,
+  Paint,
+  Skia,
+  RuntimeShader,
+  useImage,
+  useTouchHandler,
+  vec,
+} from "@shopify/react-native-skia";
+import { useDerivedValue, useSharedValue } from "react-native-reanimated";
+
+import { Slider } from "../SpeedTest/Slider";
+
+const pd = PixelRatio.get();
+
+const source = Skia.RuntimeEffect.Make(`
+uniform shader image;
+uniform vec2 screen;
+uniform vec2 touchPos;
+uniform float drawing;
+uniform float zoomLevel;
+uniform float isFixed;
+
+const vec2 magnifier_center = vec2(80);
+
+half4 main(vec2 pos) {
+    if (drawing == 0)
+        return image.eval(pos);
+
+    // Convert to UV coordinates, accounting for aspect ratio
+    vec2 uv = pos / screen.y / ${pd};
+
+    vec2 touch = touchPos.xy;
+    if (touch == vec2(0))
+        touch = screen.xy / 2 / ${pd};
+
+    // UV coordinates of touch
+    vec2 touch_uv = touch / screen.y;
+
+    // Distance to touch
+    float touch_dist = distance(uv, touch_uv);
+
+     // UV coordinates of magnifier center
+    vec2 magnifier_uv = magnifier_center / screen.y;
+
+    // Distance from magnifier to touch
+    float magnifier_touch_dist = distance(magnifier_uv, touch_uv);
+
+    if (magnifier_touch_dist < 0.1)
+        magnifier_uv.x = (screen.x / screen.y) - magnifier_uv.x;
+
+    // Distance to magnifier center
+    float magnifier_dist = distance(uv, magnifier_uv);
+
+    // Draw the texture
+    half4 fragColor = image.eval(uv * screen.y * ${pd});
+
+    if (isFixed == 1) {
+        // Draw the outline of the glass
+        if (magnifier_dist < 0.102)
+            fragColor = half4(0.01, 0.01, 0.01, 1);
+    
+        // Draw a zoomed-in version of the texture
+        if (magnifier_dist < 0.1)
+            fragColor = image.eval((touch_uv - ((magnifier_uv - uv) * zoomLevel)) * screen.y * ${pd});
+    } else {
+        // Draw the outline of the glass
+        if (touch_dist < 0.102)
+            fragColor = half4(0.01, 0.01, 0.01, 1);
+    
+        // Draw a zoomed-in version of the texture
+        if (touch_dist < 0.1)
+            fragColor = image.eval((uv + (touch_uv - uv) * (1 - zoomLevel)) * screen.y * ${pd});
+    }
+
+    return fragColor;
+}`)!;
+
+export const MagnifyingGlass = () => {
+  const canvasWidth = useSharedValue(0);
+  const canvasHeight = useSharedValue(0);
+
+  const drawing = useSharedValue(0);
+  const touchPosX = useSharedValue(0);
+  const touchPosY = useSharedValue(0);
+
+  // 1 means no zoom and 0 max
+  const zoomLevel = useSharedValue(0.4);
+
+  const [isFixed, setIsFixed] = useState(true);
+  const isFixedSharedValue = useSharedValue(1);
+
+  const image = useImage(require("../../assets/oslo2.jpg"));
+
+  const onTouch = useTouchHandler({
+    onStart: ({ x, y }) => {
+      touchPosX.value = x;
+      touchPosY.value = y;
+      drawing.value = 1;
+    },
+    onActive: ({ x, y }) => {
+      touchPosX.value = x;
+      touchPosY.value = y;
+    },
+    onEnd: () => {
+      drawing.value = 0;
+    },
+  });
+
+  const uniforms = useDerivedValue(() => {
+    return {
+      screen: vec(canvasWidth.value, canvasHeight.value),
+      touchPos: vec(touchPosX.value, touchPosY.value),
+      drawing: drawing.value,
+      zoomLevel: zoomLevel.value,
+      isFixed: isFixedSharedValue.value,
+    };
+  }, [drawing, canvasWidth, canvasHeight, zoomLevel, isFixedSharedValue]);
+
+  if (!image) {
+    return (
+      <View style={{ flex: 1, justifyContent: "center", alignItems: "center" }}>
+        <Text>Loading image...</Text>
+      </View>
+    );
+  }
+
+  const handleCanvasLayoutChange = (event: LayoutChangeEvent) => {
+    canvasWidth.value = event.nativeEvent.layout.width;
+    canvasHeight.value = event.nativeEvent.layout.height;
+  };
+
+  return (
+    <View style={{ flex: 1, flexDirection: "column-reverse" }}>
+      <Canvas
+        style={StyleSheet.absoluteFill}
+        mode="continuous"
+        onTouch={onTouch}
+        onLayout={handleCanvasLayoutChange}
+      >
+        <Group transform={[{ scale: 1 / pd }]}>
+          <Group
+            layer={
+              <Paint>
+                <RuntimeShader source={source} uniforms={uniforms} />
+              </Paint>
+            }
+            transform={[{ scale: pd }]}
+          >
+            <Image
+              image={image}
+              fit="cover"
+              x={0}
+              y={0}
+              width={canvasWidth}
+              height={canvasHeight}
+            />
+          </Group>
+        </Group>
+      </Canvas>
+      <View
+        style={{
+          height: 60,
+          flexDirection: "row",
+          justifyContent: "space-evenly",
+          alignItems: "center",
+          backgroundColor: "black",
+        }}
+      >
+        <Slider
+          initialValue={0.5}
+          minValue={1}
+          maxValue={0}
+          onValueChange={(value) => (zoomLevel.value = value)}
+        />
+        <Button
+          title={isFixed ? "Fixed" : "Following"}
+          onPress={() => {
+            setIsFixed((prev) => {
+              isFixedSharedValue.value = !prev ? 1 : 0;
+              return !prev;
+            });
+          }}
+        />
+      </View>
+    </View>
+  );
+};

example/src/Examples/MagnifyingGlass/index.tsx

@@ -0,0 +1 @@
+export { MagnifyingGlass } from "./MagnifyingGlass";

example/src/Examples/SpeedTest/Slider.tsx

@@ -14,6 +14,7 @@ interface Props {
   onValueChange: (value: number) => void;
   minValue: number;
   maxValue: number;
+  initialValue?: number;
 }
 
 const size = 32;
@@ -27,14 +28,21 @@ export const Slider: React.FC<Props> = ({
   onValueChange,
   minValue,
   maxValue,
+  initialValue = minValue,
 }) => {
   const { width } = useWindowDimensions();
 
   const sliderWidth = width / 2;
   const pickerR = size / 2;
   const progressBarHeight = 3;
 
-  const translateX = useSharedValue(-pickerR);
+  const initialTranslateX = interpolate(
+    initialValue,
+    [minValue, maxValue],
+    [-pickerR, sliderWidth - pickerR]
+  );
+
+  const translateX = useSharedValue(initialTranslateX);
   const contextX = useSharedValue(0);
   const scale = useSharedValue(1);
 

example/src/Examples/index.ts

@@ -2,6 +2,7 @@ export * from "./Reanimated";
 export * from "./API";
 export * from "./Breathe";
 export * from "./Filters";
+export * from "./MagnifyingGlass";
 export * from "./Gooey";
 export * from "./Matrix";
 export * from "./Graphs";

example/src/Home/HomeScreen.tsx

@@ -27,6 +27,11 @@ export const HomeScreen = () => {
         description="Simple Image Filters"
         route="Filters"
       />
+      <HomeScreenButton
+        title="🔍 Magnifying Glass"
+        description="Magnifying glass filter"
+        route="MagnifyingGlass"
+      />
       <HomeScreenButton
         title="🟣 Gooey Effect"
         description="Simple Gooey effect"

example/src/types.ts

@@ -8,6 +8,7 @@ export type StackParamList = {
   API: undefined;
   Breathe: undefined;
   Filters: undefined;
+  MagnifyingGlass: undefined;
   Gooey: undefined;
   Hue: undefined;
   Matrix: undefined;