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02-image.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>WebGL</title>
</head>
<body>
<canvas id="c"></canvas>
<script>
{
const createShader = (gl, type, source) => {
const shader = gl.createShader(type);
gl.shaderSource(shader, source);
gl.compileShader(shader);
const success = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
if (success) {
return shader;
}
console.error(gl.getShaderInfoLog(shader));
gl.deleteShader(shader);
};
const createProgram = (gl, vertexShader, fragmentShader) => {
const program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
const success = gl.getProgramParameter(program, gl.LINK_STATUS);
if (success) {
return program;
}
console.error(gl.getProgramInfoLog(program));
gl.deleteProgram(program);
};
const canvas = document.querySelector('#c');
const gl = canvas.getContext('webgl');
const vertexShader = createShader(gl, gl.VERTEX_SHADER, `
precision mediump float;
attribute vec2 a_position;
attribute vec2 a_texCoord;
varying vec2 uv;
void main() {
gl_Position = vec4(a_position, 1, 1);
uv = a_texCoord;
}
`);
const fragmentShader = createShader(gl, gl.FRAGMENT_SHADER, `
precision mediump float;
uniform sampler2D texture;
varying vec2 uv;
void main() {
gl_FragColor = texture2D(texture, uv);
}
`);
const program = createProgram(gl, vertexShader, fragmentShader);
const positionAttributeLocation = gl.getAttribLocation(program, "a_position");
const positionBuffer = gl.createBuffer();
const texCoordAttributeLocation = gl.getAttribLocation(program, "a_texCoord");
const texCoordBuffer = gl.createBuffer();
const init = async () => {
const imgTexture = await loadImage("images/devine_selectie-087.jpg");
gl.useProgram(program);
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array([
-1.0, 1.0,
1.0, 1.0,
-1.0, -1.0,
-1.0, -1.0,
1.0, 1.0,
1.0, -1.0
]),
gl.STATIC_DRAW);
gl.enableVertexAttribArray(positionAttributeLocation);
gl.vertexAttribPointer(positionAttributeLocation, 2, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, texCoordBuffer);
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array([
0.0, 0.0,
1.0, 0.0,
0.0, 1.0,
0.0, 1.0,
1.0, 0.0,
1.0, 1.0,
]),
gl.STATIC_DRAW);
gl.enableVertexAttribArray(texCoordAttributeLocation);
gl.vertexAttribPointer(texCoordAttributeLocation, 2, gl.FLOAT, false, 0, 0);
uploadImageToTexture(imgTexture, "texture", 0);
canvas.width = imgTexture.width;
canvas.height = imgTexture.height;
drawScene();
};
const drawScene = () => {
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.useProgram(program);
gl.drawArrays(gl.TRIANGLES, 0, 6);
requestAnimationFrame(drawScene);
};
const loadImage = (src) => {
return new Promise((resolve, reject) => {
const img = new Image();
img.addEventListener("load", () => resolve(img));
img.addEventListener("error", err => reject(err));
img.src = src;
});
};
const map = (value, x1, y1, x2, y2) => (value - x1) * (y2 - x2) / (y1 - x1) + x2;
const uploadImageToTexture = (img, uniformName, textureUnitIndex) => {
const u_imageLoc = gl.getUniformLocation(program, uniformName);
gl.uniform1i(u_imageLoc, textureUnitIndex);
const texture = gl.createTexture();
gl.activeTexture(gl.TEXTURE0 + textureUnitIndex);
gl.bindTexture(gl.TEXTURE_2D, texture);
// Set the parameters so we can render any size 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.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
// Upload the image into the texture.
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, img);
};
init();
}
</script>
</body>
</html>