如何检测鼠标位置是否悬停 [英] How to detect if mouse position is hovering
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问题描述
我有这个讨论指示如何制作铅笔工具.
I have this discussion which indicates how to make a pencil tool.
如何使用铅笔工具检测鼠标是否悬停在绘制的区域/点/图像上?然后通过在其上创建一个圆来突出显示起点和终点.
How can I detect whether the mouse is hovering on drawn area/points/images using the pencil tool? Then it will highlight the starting point and the end point by creating a circle on it.
推荐答案
您唯一的解决方案是将所有绘制的点保存到数组中,它们本身保存在包含所有路径的一个数组中:
The only solution in your case is to save all drawn points into arrays, themselves saved in one array containing all your pathes :
-
onmousedown
:创建一个新的路径数组. -
onmousemove
:
-如果绘制->用绘制的每个点填充currentPath的数组.
-else->检查鼠标的实际坐标是否在您的任何路径数组中.
onmousedown
: create a new path array.onmousemove
:
-- if drawing -> fill the currentPath's array with every drawn points.
-- else -> check if the actual mouse coordinates are in any of your path arrays.
var ctx = canvas.getContext("2d"),
painting = false,
lineThickness = 1;
canvas.width = canvas.height = 600;
var dCanvas = canvas.cloneNode(true);
dCtx = dCanvas.getContext('2d');
pCanvas = canvas.cloneNode(true);
pCtx = pCanvas.getContext('2d');
dCtx.fillStyle = "#FFF";
pCtx.fillStyle = "red";
ctx.fillRect(0, 0, 600, 600);
var pathes = [],
currentPath;
canvas.onmousedown = function(e) {
currentPath = [];
pathes.push(currentPath);
painting = true;
};
canvas.onmouseup = function(e) {
painting = false;
}
canvas.onmousemove = function(e) {
pCtx.clearRect(0, 0, canvas.width, canvas.height);
var mouseX = e.pageX - this.offsetLeft,
mouseY = e.pageY - this.offsetTop;
if (painting) {
var lastPoint = currentPath[currentPath.length-1] || {
x: e.pageX - canvas.offsetLeft,
y: e.pageY - canvas.offsetTop
};
var x1 = mouseX,
x2 = lastPoint.x,
y1 = mouseY,
y2 = lastPoint.y;
var steep = (Math.abs(y2 - y1) > Math.abs(x2 - x1));
if (steep) {
var x = x1;
x1 = y1;
y1 = x;
var y = y2;
y2 = x2;
x2 = y;
}
if (x1 > x2) {
var x = x1;
x1 = x2;
x2 = x;
var y = y1;
y1 = y2;
y2 = y;
}
var dx = x2 - x1,
dy = Math.abs(y2 - y1),
error = 0,
de = dy / dx,
yStep = -1,
y = y1;
if (y1 < y2) {
yStep = 1;
}
lineThickness = 5-Math.sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1)) / 10;
if (lineThickness < 1) {
lineThickness = 1;
}
for (var x = x1; x < x2; x++) {
if (steep) {
dCtx.fillRect(y, x, lineThickness, lineThickness);
currentPath.push({x: y,y: x});
} else {
dCtx.fillRect(x, y, lineThickness, lineThickness);
currentPath.push({x: x,y: y});
}
error += de;
if (error >= 0.5) {
y += yStep;
error -= 1.0;
}
}
currentPath.push({x: mouseX,y: mouseY});
} else {
pathes.forEach(function(path) {
if (path.some(function(point) {
return isBetween(mouseX, point.x, 5) && isBetween(mouseY, point.y, 5)
})) {
pCtx.beginPath();
pCtx.arc(path[0].x+2.5, path[0].y+2.5, 5, 0, Math.PI*2);
pCtx.fill();
pCtx.beginPath();
pCtx.arc(path[path.length-1].x+2.5, path[path.length-1].y+2.5, 5, 0, Math.PI*2);
pCtx.fill();
}
});
}
ctx.fillRect(0, 0, 600, 600);
ctx.drawImage(dCanvas, 0, 0);
ctx.drawImage(pCanvas, 0, 0);
}
function isBetween(x, y, z) {
return (x >= y - z && x <= y + z);
}
canvas {
border: 1px solid
}
<canvas id="canvas" width="500" height="500"></canvas>
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