webgl-fundamentals/webgl/webgl-2d-drawimage-04.html at master · gfxfundamentals/webgl-fundamentals · GitHub

Name: webgl-fundamentals/webgl/webgl-2d-drawimage-04.html at master · gfxfundamentals/webgl-fundamentals · GitHub
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<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
<head>
<metacharset="utf-8">
<metaname="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
<title>WebGL - 2D - DrawImage with negative widths and heights</title>
<linktype="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
</head>
<body>
<canvasid="canvas"></canvas>
</body>
<!-- vertex shader -->
<scriptid="drawImage-vertex-shader" type="x-shader/x-vertex">
attributevec4a_position;
attributevec2a_texcoord;

uniformmat4u_matrix;
uniformmat4u_textureMatrix;

varyingvec2v_texcoord;

voidmain(){
gl_Position=u_matrix*a_position;
v_texcoord=(u_textureMatrix*vec4(a_texcoord,0,1)).xy;
}
</script>
<scriptid="drawImage-fragment-shader" type="x-shader/x-fragment">
precisionmediumpfloat;

varyingvec2v_texcoord;

uniformsampler2Du_texture;

voidmain(){
gl_FragColor=texture2D(u_texture,v_texcoord);
}
</script>
<!--
for most samples webgl-utils only provides shader compiling/linking and
canvas resizing because why clutter the examples with code that's the same in every sample.
See https://webglfundamentals.org/webgl/lessons/webgl-boilerplate.html
and https://webglfundamentals.org/webgl/lessons/webgl-resizing-the-canvas.html
for webgl-utils, m3, m4, and webgl-lessons-ui.
-->
<scriptsrc="resources/webgl-utils.js"></script>
<scriptsrc="resources/m4.js"></script>
<script>
"use strict";

functionmain(){
// Get A WebGL context
/** @type {HTMLCanvasElement} */
varcanvas=document.querySelector("#canvas");
vargl=canvas.getContext("webgl");
if(!gl){
return;
}

// setup GLSL program
varprogram=webglUtils.createProgramFromScripts(gl,["drawImage-vertex-shader","drawImage-fragment-shader"]);

// look up where the vertex data needs to go.
varpositionLocation=gl.getAttribLocation(program,"a_position");
vartexcoordLocation=gl.getAttribLocation(program,"a_texcoord");

// lookup uniforms
varmatrixLocation=gl.getUniformLocation(program,"u_matrix");
vartextureMatrixLocation=gl.getUniformLocation(program,"u_textureMatrix");
vartextureLocation=gl.getUniformLocation(program,"u_texture");

// Create a buffer.
varpositionBuffer=gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER,positionBuffer);

// Put a unit quad in the buffer
varpositions=[
0,0,
0,1,
1,0,
1,0,
0,1,
1,1,
];
gl.bufferData(gl.ARRAY_BUFFER,newFloat32Array(positions),gl.STATIC_DRAW);

// Create a buffer for texture coords
vartexcoordBuffer=gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER,texcoordBuffer);

// Put texcoords in the buffer
vartexcoords=[
0,0,
0,1,
1,0,
1,0,
0,1,
1,1,
];
gl.bufferData(gl.ARRAY_BUFFER,newFloat32Array(texcoords),gl.STATIC_DRAW);

// creates a texture info { width: w, height: h, texture: tex }
// The texture will start with 1x1 pixels and be updated
// when the image has loaded
functionloadImageAndCreateTextureInfo(url){
vartex=gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D,tex);
// Fill the texture with a 1x1 blue pixel.
gl.texImage2D(gl.TEXTURE_2D,0,gl.RGBA,1,1,0,gl.RGBA,gl.UNSIGNED_BYTE,
newUint8Array([0,0,255,255]));

// let's assume all images are not a power of 2
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);

vartextureInfo={
width: 1,// we don't know the size until it loads
height: 1,
texture: tex,
};
varimg=newImage();
img.addEventListener('load',function(){
textureInfo.width=img.width;
textureInfo.height=img.height;

gl.bindTexture(gl.TEXTURE_2D,textureInfo.texture);
gl.texImage2D(gl.TEXTURE_2D,0,gl.RGBA,gl.RGBA,gl.UNSIGNED_BYTE,img);
});
img.src=url;

returntextureInfo;
}

vartextureInfos=[
loadImageAndCreateTextureInfo('resources/star.jpg'),
loadImageAndCreateTextureInfo('resources/leaves.jpg'),
loadImageAndCreateTextureInfo('resources/keyboard.jpg'),
];

vardrawInfos=[];
varnumToDraw=9;
varspeed=60;
for(varii=0;ii<numToDraw;++ii){
vardrawInfo={
x: Math.random()*gl.canvas.width,
y: Math.random()*gl.canvas.height,
dx: Math.random()>0.5 ? -1 : 1,
dy: Math.random()>0.5 ? -1 : 1,
xScale: Math.random()*0.25+0.25,
yScale: Math.random()*0.25+0.25,
offX: Math.random()*0.75,
offY: Math.random()*0.75,
textureInfo: textureInfos[Math.random()*textureInfos.length|0],
};
drawInfo.width=Math.random()*(1-drawInfo.offX);
drawInfo.height=Math.random()*(1-drawInfo.offY);
if(Math.random()>0.5){
drawInfo.xScale*=-1;
}else{
drawInfo.offX=1-drawInfo.offX;
drawInfo.width*=-1;
}
if(Math.random()>0.5){
drawInfo.yScale*=-1;
}else{
drawInfo.offY=1-drawInfo.offY;
drawInfo.height*=-1;
}
drawInfos.push(drawInfo);
}

functionupdate(deltaTime){
drawInfos.forEach(function(drawInfo){
drawInfo.x+=drawInfo.dx*speed*deltaTime;
drawInfo.y+=drawInfo.dy*speed*deltaTime;
if(drawInfo.x<0){
drawInfo.dx=1;
}
if(drawInfo.x>=gl.canvas.width){
drawInfo.dx=-1;
}
if(drawInfo.y<0){
drawInfo.dy=1;
}
if(drawInfo.y>=gl.canvas.height){
drawInfo.dy=-1;
}
});
}

functiondraw(){
webglUtils.resizeCanvasToDisplaySize(gl.canvas);

// Tell WebGL how to convert from clip space to pixels
gl.viewport(0,0,gl.canvas.width,gl.canvas.height);

gl.clear(gl.COLOR_BUFFER_BIT);

drawInfos.forEach(function(drawInfo){
vardstX=drawInfo.x;
vardstY=drawInfo.y;
vardstWidth=drawInfo.textureInfo.width*drawInfo.xScale;
vardstHeight=drawInfo.textureInfo.height*drawInfo.yScale;

varsrcX=drawInfo.textureInfo.width*drawInfo.offX;
varsrcY=drawInfo.textureInfo.height*drawInfo.offY;
varsrcWidth=drawInfo.textureInfo.width*drawInfo.width;
varsrcHeight=drawInfo.textureInfo.height*drawInfo.height;

drawImage(
drawInfo.textureInfo.texture,
drawInfo.textureInfo.width,
drawInfo.textureInfo.height,
srcX,srcY,srcWidth,srcHeight,
dstX,dstY,dstWidth,dstHeight);
});
}

varthen=0;
functionrender(time){
varnow=time*0.001;
vardeltaTime=Math.min(0.1,now-then);
then=now;

update(deltaTime);
draw();

requestAnimationFrame(render);
}
requestAnimationFrame(render);

// Unlike images, textures do not have a width and height associated
// with them so we'll pass in the width and height of the texture
functiondrawImage(
tex,texWidth,texHeight,
srcX,srcY,srcWidth,srcHeight,
dstX,dstY,dstWidth,dstHeight){
if(dstX===undefined){
dstX=srcX;
srcX=0;
}
if(dstY===undefined){
dstY=srcY;
srcY=0;
}
if(srcWidth===undefined){
srcWidth=texWidth;
}
if(srcHeight===undefined){
srcHeight=texHeight;
}
if(dstWidth===undefined){
dstWidth=srcWidth;
srcWidth=texWidth;
}
if(dstHeight===undefined){
dstHeight=srcHeight;
srcHeight=texHeight;
}

gl.bindTexture(gl.TEXTURE_2D,tex);

// Tell WebGL to use our shader program pair
gl.useProgram(program);

// Setup the attributes to pull data from our buffers
gl.bindBuffer(gl.ARRAY_BUFFER,positionBuffer);
gl.enableVertexAttribArray(positionLocation);
gl.vertexAttribPointer(positionLocation,2,gl.FLOAT,false,0,0);
gl.bindBuffer(gl.ARRAY_BUFFER,texcoordBuffer);
gl.enableVertexAttribArray(texcoordLocation);
gl.vertexAttribPointer(texcoordLocation,2,gl.FLOAT,false,0,0);

// this matrix will convert from pixels to clip space
varmatrix=m4.orthographic(0,gl.canvas.width,gl.canvas.height,0,-1,1);

// this matrix will translate our quad to dstX, dstY
matrix=m4.translate(matrix,dstX,dstY,0);

// this matrix will scale our 1 unit quad
// from 1 unit to texWidth, texHeight units
matrix=m4.scale(matrix,dstWidth,dstHeight,1);

// Set the matrix.
gl.uniformMatrix4fv(matrixLocation,false,matrix);

// Because texture coordinates go from 0 to 1
// and because our texture coordinates are already a unit quad
// we can select an area of the texture by scaling the unit quad
// down
vartexMatrix=m4.translation(srcX/texWidth,srcY/texHeight,0);
texMatrix=m4.scale(texMatrix,srcWidth/texWidth,srcHeight/texHeight,1);

// Set the texture matrix.
gl.uniformMatrix4fv(textureMatrixLocation,false,texMatrix);

// Tell the shader to get the texture from texture unit 0
gl.uniform1i(textureLocation,0);

// draw the quad (2 triangles, 6 vertices)
gl.drawArrays(gl.TRIANGLES,0,6);
}

}
main();
</script>
</html>