https://developers.weixin.qq.com/miniprogram/dev/api/canvas/Canvas.getContext.html

在微信小程序电脑端，当进行 GL 设置纹理操作时，

发现设置垂直翻转的代码 “gl.pixelStorei (gl.UNPACK_FLIP_Y_WEBGL, true)” 无论设置为 true 还是 false 都不生效。

希望能尽快得到解决。

 // 这句设置无效
  gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);

完整代码:

// wxml
<view class="container">
    <!-- 加载地图容器 -->
    <canvas type="webgl" id="testMap" style="width: 100%; height: 100%;" disable-scroll bindtouchstart="touchStart" bindtouchmove="touchMove" bindtouchend="touchEnd"></canvas>
</view>

//js
Page({
  data: {},
  onReady() {
    wx.createSelectorQuery().select('#testMap')
      .fields({ node: true, size: true })
      .exec((res) => {
        let textCanvas = res[0].node; 

        let gl = textCanvas.getContext('webgl'); 


        const vsSource = `
 attribute vec4 aVertexPosition;
 attribute vec2 aTextureCoord;
 varying highp vec2 vTextureCoord;
 void main(void) {
     gl_Position = aVertexPosition;
     vTextureCoord = aTextureCoord;
 }
`;

        // Fragment shader source code
        const fsSource = `
	 varying highp vec2 vTextureCoord;
	 uniform sampler2D uSampler;
	 void main(void) {

     gl_FragColor = texture2D(uSampler, vec2(vTextureCoord.x,1.0-vTextureCoord.y));
   
 }
`;

        // Initialize shaders
        function initShaderProgram(gl, vsSource, fsSource) {
          const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vsSource);
          const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fsSource);

          const shaderProgram = gl.createProgram();
          gl.attachShader(shaderProgram, vertexShader);
          gl.attachShader(shaderProgram, fragmentShader);
          gl.linkProgram(shaderProgram);

          if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
            alert('Unable to initialize the shader program: ' + gl.getProgramInfoLog(shaderProgram));
            return null;
          }
          return shaderProgram;
        }

        function loadShader(gl, type, source) {
          const shader = gl.createShader(type);
          gl.shaderSource(shader, source);
          gl.compileShader(shader);

          if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
            alert('An error occurred compiling the shaders: ' + gl.getShaderInfoLog(shader));
            gl.deleteShader(shader);
            return null;
          }
          return shader;
        }

        const shaderProgram = initShaderProgram(gl, vsSource, fsSource);
        const programInfo = {
          program: shaderProgram,
          attribLocations: {
            vertexPosition: gl.getAttribLocation(shaderProgram, 'aVertexPosition'),
            textureCoord: gl.getAttribLocation(shaderProgram, 'aTextureCoord'),
          },
          uniformLocations: {
            uSampler: gl.getUniformLocation(shaderProgram, 'uSampler'),
          },
        };

        // Initialize buffers
        const positionBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
        const positions = [
            -1.0, 1.0,
            1.0, 1.0,
            -1.0, -1.0,
            1.0, -1.0,
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);

        const textureCoordBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, textureCoordBuffer);
        const textureCoordinates = [
            0.0, 0.0,
            1.0, 0.0,
            0.0, 1.0,
            1.0, 1.0,
        ];
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoordinates), gl.STATIC_DRAW);

        // Load texture
        function loadTexture(gl, cb) {
          const texture = gl.createTexture();
          gl.bindTexture(gl.TEXTURE_2D, texture);

          const level = 0;
          const internalFormat = gl.RGBA;
          const srcFormat = gl.RGBA;
          const srcType = gl.UNSIGNED_BYTE;

          const image = textCanvas.createImage();
          image.onload = function () {
            gl.bindTexture(gl.TEXTURE_2D, texture);
            // 这句设置无效
            gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
            gl.texImage2D(gl.TEXTURE_2D, level, internalFormat, srcFormat, srcType, image);

            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
            gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);

            cb();
          };
          image.src = 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pyO1Yy/UA7eJotpQBkgNR4Gd4TDGnwWDVn/AOdLCf8APn+M5z/PnPn+f+efdxzMqjVRYK0pIA8qiKJMEYEpq1n27KEz1iOYW+/bZEzyXLyiZkYGBxOvWnoiq1xmgbb70LIpkYtWa9Oq90dpmYJiKFRZRHA8IGYiCkpJxxxyXqJpxxxw0accccNGnHHHDRpxxxw0accccNGv/9k=';

          return texture;
        }

        const texture = loadTexture(gl, () => {
          render();
        });

        // Draw the scene
        function drawScene(gl, programInfo, buffers, texture) {
          gl.clearColor(0.0, 0.0, 0.0, 1.0);
          gl.clear(gl.COLOR_BUFFER_BIT);

          gl.useProgram(programInfo.program);

          gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
          gl.vertexAttribPointer(programInfo.attribLocations.vertexPosition, 2, gl.FLOAT, false, 0, 0);
          gl.enableVertexAttribArray(programInfo.attribLocations.vertexPosition);

          gl.bindBuffer(gl.ARRAY_BUFFER, textureCoordBuffer);
          gl.vertexAttribPointer(programInfo.attribLocations.textureCoord, 2, gl.FLOAT, false, 0, 0);
          gl.enableVertexAttribArray(programInfo.attribLocations.textureCoord);

          gl.activeTexture(gl.TEXTURE0);
          gl.bindTexture(gl.TEXTURE_2D, texture);
          gl.uniform1i(programInfo.uniformLocations.uSampler, 0);

          gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
        }

        function render() {
          drawScene(gl, programInfo, { position: positionBuffer, textureCoord: textureCoordBuffer }, texture);
        }

        render();
      })
  },
})