canvas代码特效花瓣落下的效果_canvas撒花,canvas画花瓣资源-CSDN文库

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html：2个

jpg：1个

需积分: 50 15 浏览量 2018-05-21 19:29:11 上传评论 1 收藏 2.86MB ZIP 举报

在本文中，我们将深入探讨如何使用HTML5的canvas元素创建花瓣落下的视觉特效。canvas是HTML5中的一个强大特性，允许开发者通过JavaScript绘制图形，实现动态和交互式的网页内容。这个"花瓣雨"特效就是一个很好的例子，展示了canvas在前端开发中的潜力。要创建花瓣落下的效果，我们需要在HTML文档中引入canvas元素。在HTML中，可以这样声明一个canvas： ```html <canvas id="myCanvas" width="800" height="600"></canvas> ``` 这里的`id`属性用于在JavaScript中引用canvas，`width`和`height`定义了画布的尺寸。接下来，我们需要使用JavaScript来操作canvas。通过获取canvas元素并创建一个`CanvasRenderingContext2D`对象，我们可以开始绘制。在JavaScript中，这通常如下所示： ```javascript var canvas = document.getElementById('myCanvas'); var ctx = canvas.getContext('2d'); ``` 现在我们有了一个可以绘制的画布，可以开始编写花瓣的逻辑。每个花瓣都是一个独立的对象，包含它的位置、大小、颜色等属性。创建一个花瓣类，然后实例化多个花瓣对象： ```javascript function Petal(x, y, size, color) { this.x = x; this.y = y; this.size = size; this.color = color; // 其他属性和方法... } // 创建花瓣数组 var petals = []; for (var i = 0; i < 100; i++) { var petal = new Petal(Math.random() * canvas.width, Math.random() * canvas.height, 30 + Math.random() * 20, 'pink'); petals.push(petal); } ``` 接着，我们需要一个动画循环来更新花瓣的位置，并在canvas上重绘它们。这通常在`requestAnimationFrame`函数中实现，它会以浏览器的最佳帧率执行回调函数： ```javascript function animate() { requestAnimationFrame(animate); // 更新花瓣的位置 for (var i = 0; i < petals.length; i++) { var petal = petals[i]; petal.y += petal.speed || 1; if (petal.y > canvas.height) { petal.y = -petal.size; } } // 清除画布并重新绘制花瓣 ctx.clearRect(0, 0, canvas.width, canvas.height); for (var i = 0; i < petals.length; i++) { var petal = petals[i]; ctx.beginPath(); ctx.fillStyle = petal.color; ctx.arc(petal.x, petal.y, petal.size / 2, 0, Math.PI * 2, true); ctx.fill(); } } animate(); ``` 在这个例子中，花瓣会从随机位置以一定的速度落下，当它们到达画布底部时会重新出现在顶部，模拟花瓣飘落的效果。你可以根据需要调整花瓣的形状、颜色、速度以及数量，以达到不同的视觉效果。这个"花瓣雨"特效不仅适用于个人网页或简历介绍，还是一种很好的学习资源，可以帮助前端开发者掌握canvas和JavaScript的基本概念，进一步理解HTML5的动态图形和动画制作。通过这样的练习，开发者可以提高对前端技术的理解，为构建更复杂的交互式Web应用打下基础。

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canvas.zip （3个子文件）

花瓣

BG.jpg 2.84MB

2.html 34KB

花瓣雨

index.html 33KB

<!doctype html> <html> <head> <meta charset="utf-8"> <title>无标题文档</title> </head> <style> body { padding:0; margin:0; overflow:hidden; background-image:url(BG.jpg); background-position: center center; background-repeat: no-repeat; background-size: cover; } canvas { padding:0; margin:0; opacity:0.25; } div.btnbg { position:fixed; left:0; top:0; } </style> <body> <canvas id="sakura"></canvas> <div class="btnbg"> </div>  <script id="sakura_point_vsh" type="x-shader/x_vertex"> uniform mat4 uProjection; uniform mat4 uModelview; uniform vec3 uResolution; uniform vec3 uOffset; uniform vec3 uDOF; //x:focus distance, y:focus radius, z:max radius uniform vec3 uFade; //x:start distance, y:half distance, z:near fade start attribute vec3 aPosition; attribute vec3 aEuler; attribute vec2 aMisc; //x:size, y:fade varying vec3 pposition; varying float psize; varying float palpha; varying float pdist; //varying mat3 rotMat; varying vec3 normX; varying vec3 normY; varying vec3 normZ; varying vec3 normal; varying float diffuse; varying float specular; varying float rstop; varying float distancefade; void main(void) { // Projection is based on vertical angle vec4 pos = uModelview * vec4(aPosition + uOffset, 1.0); gl_Position = uProjection * pos; gl_PointSize = aMisc.x * uProjection[1][1] / -pos.z * uResolution.y * 0.5; pposition = pos.xyz; psize = aMisc.x; pdist = length(pos.xyz); palpha = smoothstep(0.0, 1.0, (pdist - 0.1) / uFade.z); vec3 elrsn = sin(aEuler); vec3 elrcs = cos(aEuler); mat3 rotx = mat3( 1.0, 0.0, 0.0, 0.0, elrcs.x, elrsn.x, 0.0, -elrsn.x, elrcs.x ); mat3 roty = mat3( elrcs.y, 0.0, -elrsn.y, 0.0, 1.0, 0.0, elrsn.y, 0.0, elrcs.y ); mat3 rotz = mat3( elrcs.z, elrsn.z, 0.0, -elrsn.z, elrcs.z, 0.0, 0.0, 0.0, 1.0 ); mat3 rotmat = rotx * roty * rotz; normal = rotmat[2]; mat3 trrotm = mat3( rotmat[0][0], rotmat[1][0], rotmat[2][0], rotmat[0][1], rotmat[1][1], rotmat[2][1], rotmat[0][2], rotmat[1][2], rotmat[2][2] ); normX = trrotm[0]; normY = trrotm[1]; normZ = trrotm[2]; const vec3 lit = vec3(0.6917144638660746, 0.6917144638660746, -0.20751433915982237); float tmpdfs = dot(lit, normal); if(tmpdfs < 0.0) { normal = -normal; tmpdfs = dot(lit, normal); } diffuse = 0.4 + tmpdfs; vec3 eyev = normalize(-pos.xyz); if(dot(eyev, normal) > 0.0) { vec3 hv = normalize(eyev + lit); specular = pow(max(dot(hv, normal), 0.0), 20.0); } else { specular = 0.0; } rstop = clamp((abs(pdist - uDOF.x) - uDOF.y) / uDOF.z, 0.0, 1.0); rstop = pow(rstop, 0.5); //-0.69315 = ln(0.5) distancefade = min(1.0, exp((uFade.x - pdist) * 0.69315 / uFade.y)); } </script> <script id="sakura_point_fsh" type="x-shader/x_fragment"> #ifdef GL_ES //precision mediump float; precision highp float; #endif uniform vec3 uDOF; //x:focus distance, y:focus radius, z:max radius uniform vec3 uFade; //x:start distance, y:half distance, z:near fade start const vec3 fadeCol = vec3(0.08, 0.03, 0.06); varying vec3 pposition; varying float psize; varying float palpha; varying float pdist; //varying mat3 rotMat; varying vec3 normX; varying vec3 normY; varying vec3 normZ; varying vec3 normal; varying float diffuse; varying float specular; varying float rstop; varying float distancefade; float ellipse(vec2 p, vec2 o, vec2 r) { vec2 lp = (p - o) / r; return length(lp) - 1.0; } void main(void) { vec3 p = vec3(gl_PointCoord - vec2(0.5, 0.5), 0.0) * 2.0; vec3 d = vec3(0.0, 0.0, -1.0); float nd = normZ.z; //dot(-normZ, d); if(abs(nd) < 0.0001) discard; float np = dot(normZ, p); vec3 tp = p + d * np / nd; vec2 coord = vec2(dot(normX, tp), dot(normY, tp)); //angle = 15 degree const float flwrsn = 0.258819045102521; const float flwrcs = 0.965925826289068; mat2 flwrm = mat2(flwrcs, -flwrsn, flwrsn, flwrcs); vec2 flwrp = vec2(abs(coord.x), coord.y) * flwrm; float r; if(flwrp.x < 0.0) { r = ellipse(flwrp, vec2(0.065, 0.024) * 0.5, vec2(0.36, 0.96) * 0.5); } else { r = ellipse(flwrp, vec2(0.065, 0.024) * 0.5, vec2(0.58, 0.96) * 0.5); } if(r > rstop) discard; vec3 col = mix(vec3(1.0, 0.8, 0.75), vec3(1.0, 0.9, 0.87), r); float grady = mix(0.0, 1.0, pow(coord.y * 0.5 + 0.5, 0.35)); col *= vec3(1.0, grady, grady); col *= mix(0.8, 1.0, pow(abs(coord.x), 0.3)); col = col * diffuse + specular; col = mix(fadeCol, col, distancefade); float alpha = (rstop > 0.001)? (0.5 - r / (rstop * 2.0)) : 1.0; alpha = smoothstep(0.0, 1.0, alpha) * palpha; gl_FragColor = vec4(col * 0.5, alpha); } </script>  <script id="fx_common_vsh" type="x-shader/x_vertex"> uniform vec3 uResolution; attribute vec2 aPosition; varying vec2 texCoord; varying vec2 screenCoord; void main(void) { gl_Position = vec4(aPosition, 0.0, 1.0); texCoord = aPosition.xy * 0.5 + vec2(0.5, 0.5); screenCoord = aPosition.xy * vec2(uResolution.z, 1.0); } </script> <script id="bg_fsh" type="x-shader/x_fragment"> #ifdef GL_ES //precision mediump float; precision highp float; #endif uniform vec2 uTimes; varying vec2 texCoord; varying vec2 screenCoord; void main(void) { vec3 col; float c; vec2 tmpv = texCoord * vec2(3, 0.9) - vec2(0.95, 1); c = exp(-pow(length(tmpv) * 1.5, 0.3)); col = mix(vec3(0, 0, 0), vec3(1,1,1) * 1.5, c); gl_FragColor = vec4(col * 0.5, 1.0); } </script> <script id="fx_brightbuf_fsh" type="x-shader/x_fragment"> #ifdef GL_ES //precision mediump float; precision highp float; #endif uniform sampler2D uSrc; uniform vec2 uDelta; varying vec2 texCoord; varying vec2 screenCoord; void main(void) { vec4 col = texture2D(uSrc, texCoord); gl_FragColor = vec4(col.rgb * 2.0 - vec3(0.5), 1.0); } </script> <script id="fx_dirblur_r4_fsh" type="x-shader/x_fragment"> #ifdef GL_ES //precision mediump float; precision highp float; #endif uniform sampler2D uSrc; uniform vec2 uDelta; uniform vec4 uBlurDir; //dir(x, y), stride(z, w) varying vec2 texCoord; varying vec2 screenCoord; void main(void) { vec4 col = texture2D(uSrc, texCoord); col = col + texture2D(uSrc, texCoord + uBlurDir.xy * uDelta); col = col + texture2D(uSrc, texCoord - uBlurDir.xy * uDelta); col = col + texture2D(uSrc, texCoord + (uBlurDir.xy + uBlurDir.zw) * uDelta); col = col + texture2D(uSrc, texCoord - (uBlurDir.xy + uBlurDir.zw) * uDelta); gl_FragColor = col / 5.0; } </script>  <script id="fx_common_fsh" type="x-shader/x_fragment"> #ifdef GL_ES //precision mediump float; precision highp float; #endif uniform sampler2D uSrc; uniform vec2 uDelta; varying vec2 texCoord; varying vec2 screenCoord; void main(void) { gl_FragColor = texture2D(uSrc, texCoord); } </script>  <script id="pp_final_vsh" type="x-shader/x_vertex"> uniform vec3 uResolution; attribute vec2 aPosition; varying vec2 texCoord; varying vec2 screenCoord; void main(void) { gl_Position = vec4(aPosition, 0.0, 1.0); texCoord = aPosition.xy * 0.5 + vec2(0.5, 0.5); screenCoord = aPosition.xy * vec2(uResolution.z, 1.0); } </script> <script id="pp_final_fsh" type="x-shader/x_fragment"> #ifdef GL_ES //precision mediump float; precision highp float; #endif uniform sampler2D uSrc; uniform sampler2D uBloom; uniform vec2 uDelta

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