index.vert

#version 300 es

in vec2 aVertexTextureCoords;
in vec3 aVertexPosition;

uniform mat4 uModelViewMatrix;
uniform mat4 uProjectionMatrix;

out vec2 vTextureCoords;

void main() {
  vTextureCoords = aVertexTextureCoords;
  gl_Position = vec4(aVertexPosition, 1.0);
}

index.frag

#version 300 es

precision highp float;

vec4 mosaicByAverage(sampler2D tex, vec2 texSize, vec2 center, int mosaicScale) {
  vec4 sumColor = vec4(0.0);
  
  for (int i = 0; i < mosaicScale; i++) {
    for (int j = 0; j < mosaicScale; j++) {
      vec2 offset = vec2(float(i), float(j)) / texSize;
      vec2 coord = center + offset;
      vec4 color = texture(tex, coord);
      sumColor += color.a < 0.1 ? vec4(0.0) : color;
    }
  }
  
  vec4 averageColor = sumColor / float(mosaicScale * mosaicScale);
  
  return averageColor;
}

uniform sampler2D uTexture0;
uniform int uMosaicScale;

in vec2 vTextureCoords;

out vec4 fragColor;

void main() {
  ivec2 iTextureSize = textureSize(uTexture0, 0);
  vec2 texSize = vec2(float(iTextureSize.x), float(iTextureSize.y));
  vec2 texCoord = vec2(vTextureCoords.x, 1.0 - vTextureCoords.y);
  
  float mosaicScale = float(uMosaicScale);
  vec2 center = floor(texCoord * texSize / mosaicScale) / (texSize / mosaicScale) + (mosaicScale * 0.5) / texSize;
  
  vec4 finalColor = mosaicByAverage(uTexture0, texSize, center, uMosaicScale);
  
  fragColor = finalColor;
}

render.ts

import { Space } from "@/lib/canvas/index"
import { Program } from "@/lib/webgl/program"
import { Scene } from "@/lib/webgl/scene"
import { Clock } from "@/lib/event/clock"
import { ControlUi } from "@/lib/gui/control-ui"
import { Texture } from "@/lib/webgl/texture"
import { UniformLoader } from "@/lib/webgl/uniform-loader"

import mainVertSrc from "./index.vert?raw"
import mainFragSrc from "./index.frag?raw"

import imageGeometry from "@/assets/original/pastel-tomixy.png"
import imageAutumnLeaves from "@/assets/original/autumn-leaves_00037.jpg"
import imageWater from "@/assets/original/water_00032.jpg"
import imageFireworks from "@/assets/original/fireworks_00018.jpg"

export const onload = () => {
  const space = new Space("gl-canvas")
  const canvas = space.canvas
  const gl = space.gl
  if (!canvas || !gl) return

  let scene: Scene
  let program: Program
  let clock: Clock
  let textures: Texture[] = []

  const uniforms = new UniformLoader(gl, ["uMosaicScale"])

  const images = [
    { name: "花火", image: imageFireworks },
    { name: "立方体", image: imageGeometry },
    { name: "紅葉", image: imageAutumnLeaves },
    { name: "水面", image: imageWater }
  ]
  const imageNames = images.map((obj) => obj.name)
  let activeImage = 1

  const defaultMosaicScale = 10

  const initGuiControls = () => {
    const ui = new ControlUi()
    ui.select("Image", images[activeImage].name, imageNames, (name) => {
      const idx = imageNames.indexOf(name)
      if (idx < 0) return
      activeImage = idx
      space.fitImage(textures[activeImage].image)
    })
    ui.number("MosaicScale", defaultMosaicScale, 1, 50, 2, (value) => {
      uniforms.int("uMosaicScale", value)
    })
  }

  const onResize = () => {
    space.fitImage(textures[activeImage].image)
    render()
  }

  const configure = async () => {
    gl.clearColor(1.0, 0.0, 0.0, 1.0)
    gl.clearDepth(1.0)

    program = new Program(gl, mainVertSrc, mainFragSrc)

    scene = new Scene(gl, program)
    clock = new Clock()

    await Promise.all(
      images.map(async (obj) => {
        const texture = new Texture(gl, program, obj.image)
        textures.push(texture)
        await texture.load()
      })
    )

    uniforms.init(program)
    uniforms.int("uMosaicScale", defaultMosaicScale)

    space.fitImage(textures[activeImage].image)
    space.onResize = onResize
  }

  const registerGeometry = () => {
    // 画面を覆う板ポリゴン
    const vertices = [-1.0, 1.0, 0.0, 1.0, 1.0, 0.0, -1.0, -1.0, 0.0, 1.0, -1.0, 0.0]
    const texCoords = [0.0, 0.0, 1.0, 0.0, 0.0, 1.0, 1.0, 1.0]
    const indices = [0, 2, 1, 2, 3, 1]
    scene.add({ vertices, indices, texCoords })
  }

  const render = () => {
    gl.viewport(0, 0, gl.canvas.width, gl.canvas.height)
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)

    scene.traverseDraw((obj) => {
      obj.bind()

      textures[activeImage].use()
      gl.drawElements(gl.TRIANGLES, obj.indices.length, gl.UNSIGNED_SHORT, 0)

      obj.cleanup()
    })
  }

  const init = async () => {
    await configure()
    registerGeometry()
    clock.on("tick", render)

    initGuiControls()
  }

  init()
}