HTML5 Canvas实现放大镜效果示例

function drawLines() { var line; context.lineWidth = 1; for (var i = 0; i < chartLines.length; i++) { line = chartLines[i]; context.beginPath(); context.strokeStyle = line.color; context.moveTo(line.xStart, line.yStart); context.lineTo(line.xEnd, line.yEnd); context.stroke(); } }

计算原始区域和放大镜区域

function calGlassRectangle(point) { originalRectangle.x = point.x - originalRadius; originalRectangle.y = point.y - originalRadius; originalRectangle.width = originalRadius * 2; originalRectangle.height = originalRadius * 2; scaleGlassRectangle.width = originalRectangle.width * scale; scaleGlassRectangle.height = originalRectangle.height * scale; scaleGlassRectangle.x = originalRectangle.x + originalRectangle.width / 2 - scaleGlassRectangle.width / 2; scaleGlassRectangle.y = originalRectangle.y + originalRectangle.height / 2 - scaleGlassRectangle.height / 2; // 将值装换为整数 scaleGlassRectangle.width = parseInt(scaleGlassRectangle.width); scaleGlassRectangle.height = parseInt(scaleGlassRectangle.height); scaleGlassRectangle.x = parseInt(scaleGlassRectangle.x); scaleGlassRectangle.y = parseInt(scaleGlassRectangle.y); }

计算线段在新坐标系统的位置

由原理图我们知道，放大镜中使用坐标系的图例要比原始坐标系更加精确，比如原始坐标系使用 1:100，那么放大镜坐标系使用 1:10，因此我们需要重新计算线段在放大镜坐标系中的位置。同时为了简便，我们将线段的原始坐标进行了转化，减去原始区域起始的x值和y值，即将原始区域左上角的点看做为(0,0)。

function calScaleLines() { var xStart = originalRectangle.x; var xEnd = originalRectangle.x + originalRectangle.width; var yStart = originalRectangle.y; var yEnd = originalRectangle.y + originalRectangle.height; var line, gLine, sgLine; var glassLineIndex = 0; for (var i = 0; i < chartLines.length; i++) { line = chartLines[i]; // 判断线段是否在放大镜中 if (line.xStart < xStart || line.xEnd > xEnd) { continue; } if (line.yEnd > yEnd || line.yStart < yStart) { continue; } gLine = glassLines[glassLineIndex]; sgLine = scaleGlassLines[glassLineIndex]; if (line.yEnd > yEnd) { gLine.yEnd = yEnd; } if (line.yStart < yStart) { gLine.yStart = yStart; } gLine.xStart = line.xStart - xStart; gLine.yStart = line.yStart - yStart; gLine.xEnd = line.xEnd - xStart; gLine.yEnd = line.yEnd - yStart; sgLine.xStart = parseInt(gLine.xStart * scale); sgLine.yStart = parseInt(gLine.yStart * scale); sgLine.xEnd = parseInt(gLine.xEnd * scale); sgLine.yEnd = parseInt(gLine.yEnd * scale); sgLine.color = line.color; glassLineIndex++; } glassLineSize = glassLineIndex; }

绘制放大镜中心点

绘制放大镜中心的瞄准器

function drawAnchor() { context.beginPath(); context.lineWidth = 2; context.fillStyle = "#fff"; context.strokeStyle = "#000"; context.arc(parseInt(centerPoint.x), parseInt(centerPoint.y), 10, 0, Math.PI * 2, false); var radius = 15; context.moveTo(parseInt(centerPoint.x - radius), parseInt(centerPoint.y)); context.lineTo(parseInt(centerPoint.x + radius), parseInt(centerPoint.y)); context.moveTo(parseInt(centerPoint.x), parseInt(centerPoint.y - radius)); context.lineTo(parseInt(centerPoint.x), parseInt(centerPoint.y + radius)); //context.fill(); context.stroke(); }

绘制放大镜

（编辑：济南站长网）

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!