| 标题 | HTML5 Canvas实现图片缩放、翻转、颜色渐变的代码示例 |
| 范文 | 这篇文章主要介绍了HTML5 Canvas实现图片缩放、翻转、颜色渐变的代码示例,充分利用到了坐标的操作,说明都写在代码注释里了很简明,需要的朋友可以参考下 翻转、移动、平移、放大、缩小 XML/HTML Code var canvas = document.getElementById('canvas'); if (canvas.getContext) { var context = canvas.getContext('2d'); // 放大与缩小 context.beginPath(); context.strokeStyle = "#000000"; context.strokeRect(10,10,150,100); // 放大3倍 context.scale(3,3); context.beginPath(); context.strokeStyle = '#cccccc'; context.strokeRect(10,10,150,100) // 缩小 context.scale(0.5,0.5); context.beginPath(); context.strokeStyle = '#cccccc'; context.strokeRect(10,10,150,100) // 翻转 var img = new Image(); img.src = 'images/1.jpg'; img.onload = function(){ context.drawImage(img, 10,10); context.scale(1, -1); context.drawImage(img, 0, -500); } // 平移 context.beginPath(); context.strokeStyle = '#000000'; context.strokeRect(10,101,150,100); // x移动 50 y 移动100 context.translate(50,100); context.beginPath(); context.strokeStyle = '#cccccc'; context.strokeRect(10,10,150,100); // 旋转 context.beginPath(); context.strokeStyle = '#000000'; context.strokeRect(200,50,100,50); // 默认旋转是根据0,0中心，使用translate可以按照自己的设置的中心旋转 context.translate(250,75); context.rotate(45 * Math.PI /180); context.translate(-250, -75); context.beginPath(); context.strokeStyle = '#cccccc'; context.strokeRect(200,50,100,50); // transform 矩阵 context.beginPath(); context.strokeStyle = '#000000'; context.strokeRect(10,10,150,100); context.transform(3,0,0,3,0,0); context.beginPath(); context.strokeStyle = '#cccccc'; context.strokeRect(10,10,150,100); } 渐变、图像组合效果、颜色翻转 XML/HTML Code var canvas = document.getElementById('canvas'); if (canvas.getContext) { var context = canvas.getContext('2d'); // 线性绘制渐变 var grd = context.createLinearGradient(0,0,200,100); // postion 必须是0.1-1.0之间的竖直，表示渐变中颜色的地点相对地位，color表示颜色 grd.addColorStop(0.1, "#00ff00"); grd.addColorStop(0.8, "#ff0000"); context.fillStyle = grd; context.fillRect(0,0, 200,100); // 径向渐变 var grd = context.createRadialGradient(100,100,10,100,100,50); grd.addColorStop(0.1, "#00ff00"); grd.addColorStop(0.8, '#ff0000'); context.fillStyle = grd; context.fillRect(0,0,200,200); // 图像组合效果 context.fillStyle = '#00ff00'; context.fillRect(10,10,50,50); // 新绘图 //context.globalCompositeOperation = "source-over"; // 只绘制新内容，删除其他所有内容 context.globalCompositeOperation = 'copy'; // 图形重叠的地方，其颜色值相减后决定 context.globalCompositeOperation = 'darker'; // 画布上已经有的内容只会载和其他图形重叠的地方保留 context.globalCompositeOperation = 'destination-atop'; // 参考 http://www.w3school.com.cn/htmldom/prop_canvasrenderingcontext2d_globalcompositeoperation.asp context.beginPath(); context.fillStyle = '#ff0000'; context.arc(50,50,30,0, 2 * Math.PI); context.fill(); // 颜色翻转 var img = new Image(); img.src = 'images/1.jpg'; img.onload = function(){ context.drawImage(img, 0,0, 1, 1); var imgData = context.getImageData(0,0, 1,1); var pixels = imgData.data; console.log(pixels); for(var i = 0, n = pixels.length; i < n; i+=4) { pixels[i] = 255 - pixels[i]; pixels[i+1] = 255 - pixels[i + 1]; pixels[i+2] = 255 - pixels[i + 2]; } context.putImageData(imgData, 250, 0); } } |
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