webgl-tutorial/webgl_12_texture.html at master · Paweled/webgl-tutorial · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8"/>
    <title>texture</title>
</head>
<body>

<canvas id="canvas" width="400" height="400">
    Please use a browser that supports "canvas"
</canvas>

<script>
    // vertex shader
    var VERTEX_SHADER_SOURCE =
        'attribute vec4 a_Position;\n' +
        'attribute vec2 a_TexCoord;\n' +
        'varying vec2 v_TexCoord;\n' +

        'void main() {\n' +
        '   gl_Position = a_Position;\n' +
        '   v_TexCoord = a_TexCoord;\n' +
        '}\n';

    // fragment shader
    var FRAGMENT_SHADER_SOURCE =
        'precision mediump float;\n' +
        'varying vec2 v_TexCoord;\n' +
        'uniform sampler2D u_Sampler;\n' +

        'void main() {\n' +
        '   gl_FragColor = texture2D(u_Sampler, v_TexCoord);\n' +
        '}\n';

    var canvas = document.getElementById("canvas");
    var gl = canvas.getContext('webgl');
    gl.clearColor(0.0, 0.0, 0.0, 1.0);

    if (!initShaders(gl, VERTEX_SHADER_SOURCE, FRAGMENT_SHADER_SOURCE)) {
        alert('Failed to init shaders');
    }

    var vertices = new Float32Array([
        -0.5, 0.5, 0.0, 1.0, // 前 2 位是位置坐标， 后 2 位是纹理坐标
        -0.5, -0.5, 0.0, 0.0,
        0.5, 0.5, 1.0, 1.0,
        0.5, -0.5, 1.0, 0.0
    ]);

    initVertexBuffers(gl, vertices);

    var image = new Image();
    image.onload = function () {
        loadTexture(image);
        draw();
    };
    image.src = 'images/sky.jpg';

    function initVertexBuffers(gl, vertices) {
        var vertexBuffer = gl.createBuffer();
        if (!vertexBuffer) {
            console.log('Failed to create buffer object');
            return -1;
        }

        gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
        gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);

        var FSIZE = vertices.BYTES_PER_ELEMENT;

        var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
        gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, 4 * FSIZE, 0);
        gl.enableVertexAttribArray(a_Position);

        var a_TexCoord = gl.getAttribLocation(gl.program, 'a_TexCoord');
        gl.vertexAttribPointer(a_TexCoord, 2, gl.FLOAT, false, 4 * FSIZE, 2 * FSIZE);
        gl.enableVertexAttribArray(a_TexCoord);
    }

    function loadTexture(image) {
        var texture = gl.createTexture();
        // 翻转 Y 轴
        gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, 1);
        gl.activeTexture(gl.TEXTURE0);
        gl.bindTexture(gl.TEXTURE_2D, texture);

        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, gl.RGB, gl.UNSIGNED_BYTE, image);

        var u_Sampler = gl.getUniformLocation(gl.program, 'u_Sampler');
        gl.uniform1i(u_Sampler, 0);
    }

    function draw() {
        gl.clear(gl.COLOR_BUFFER_BIT);
        gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
    }

    function initShaders(gl, vertexShaderSource, fragmentShaderSource) {
        var program = createProgram(gl, vertexShaderSource, fragmentShaderSource);
        if (!program) {
            console.log('Failed to create program');
            return false;
        }

        gl.useProgram(program);
        gl.program = program;

        return true;
    }

    function loadShader(gl, type, source) {
        // create shader object
        var shader = gl.createShader(type);
        if (shader == null) {
            console.log('unable to create shader');
            return null;
        }

        // set shader source code
        gl.shaderSource(shader, source);

        // compile the shader
        gl.compileShader(shader);

        // check compile status
        var compiled = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
        if (!compiled) {
            var error = gl.getShaderInfoLog(shader);
            console.log('Failed to compile shader: ' + error);
            return null;
        }

        return shader;
    }

    function createProgram(gl, vertexShaderSource, fragmentShaderSource) {
        var vertexShader = loadShader(gl, gl.VERTEX_SHADER, vertexShaderSource);
        var fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fragmentShaderSource);
        if (!vertexShader || !fragmentShader) {
            return null;
        }

        // create a program object
        var program = gl.createProgram();
        if (!program) {
            console.log('gl.createProgram failed');
            return null;
        }

        // attach  the shader objects
        gl.attachShader(program, vertexShader);
        gl.attachShader(program, fragmentShader);

        // link the program object
        gl.linkProgram(program);

        // check link status
        var linked = gl.getProgramParameter(program, gl.LINK_STATUS);
        if (!linked) {
            var error = gl.getProgramInfoLog(program);
            console.log('Failed to link program: ' + error);
            gl.deleteProgram(program);
            gl.deleteShader(vertexShader);
            gl.deleteShader(fragmentShader);
            return null;
        }

        return program;
    }

</script>
</body>
</html>