编辑纹理颜色 - WebGL

我使用 WebGL 在一个简单的立方体上应用了纹理。纹理是一个有 2 种颜色的棋盘；这是结果：

我想知道如何只为某些像素编辑纹理的颜色，以便使用不同的颜色在这个立方体上获得眼睛或嘴巴之类的东西。

这是我用来构建检查板的代码：

var colorsArray = [];

var vertexColors = [
                    vec4( 1.0, 0.0, 1.0, 1.0 ),  //
                    vec4( 1.0, 1.0, 1.0, 1.0 ),  //
                    vec4( 1.0, 0.0, 1.0, 1.0 ),  //
                    vec4( 1.0, 1.0, 1.0, 1.0 ),  //
                    vec4( 1.0, 0.0, 1.0, 1.0 ),  //
                    vec4( 1.0, 1.0, 1.0, 1.0 ),  //
                    vec4( 1.0, 1.0, 1.0, 1.0 ),  //
                    vec4( 1.0, 1.0, 1.0, 1.0 )   //
                    ];

var move_forward = false;

// TEXTURE
var texSize = 256;
var numChecks = 8;
var c;

var image1 = new Uint8Array(4*texSize*texSize);

for ( var i = 0; i < texSize; i++ ) {
    for ( var j = 0; j <texSize; j++ ) {
        var patchx = Math.floor(i/(texSize/numChecks));
        var patchy = Math.floor(j/(texSize/numChecks));
        if(patchx%2 ^ patchy%2) c = 255;
        else c = 0;
        //c = 255*(((i & 0x8) == 0) ^ ((j & 0x8)  == 0))
        image1[4*i*texSize+4*j] = c;
        image1[4*i*texSize+4*j+1] = c;
        image1[4*i*texSize+4*j+2] = c;
        image1[4*i*texSize+4*j+3] = 255;
    }
}

var image2 = new Uint8Array(4*texSize*texSize);

// Create a checkerboard pattern
for ( var i = 0; i < texSize; i++ ) {
    for ( var j = 0; j <texSize; j++ ) {
        image2[4*i*texSize+4*j] = 127+127*Math.sin(0.1*i*j);
        image2[4*i*texSize+4*j+1] = 127+127*Math.sin(0.1*i*j);
        image2[4*i*texSize+4*j+2] = 127+127*Math.sin(0.1*i*j);
        image2[4*i*texSize+4*j+3] = 255;
    }
}

var texture1, texture2;
var t1, t2;

var texCoordsArray = [];

var texCoord = [
                vec2(0, 0),
                vec2(0, 1),
                vec2(1, 1),
                vec2(1, 0)
                ];

function configureTexture() {
    texture1 = gl.createTexture();
    gl.bindTexture( gl.TEXTURE_2D, texture1 );
    gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, texSize, texSize, 0, gl.RGBA, gl.UNSIGNED_BYTE, image1);
    gl.generateMipmap( gl.TEXTURE_2D );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER,
                     gl.NEAREST_MIPMAP_LINEAR );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);

    texture2 = gl.createTexture();
    gl.bindTexture( gl.TEXTURE_2D, texture2 );
    gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, texSize, texSize, 0, gl.RGBA, gl.UNSIGNED_BYTE, image2);
    gl.generateMipmap( gl.TEXTURE_2D );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER,
                     gl.NEAREST_MIPMAP_LINEAR );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
}