我正在尝试制作一条从左到右穿过 Canvas 的线。我仍处于实现该目标的早期阶段,我正在使用以下功能来执行逐步动画
timer = window.setInterval(draw_line, 30);
我的绘图函数是这样的
function draw_line()
{
context.fillStyle = "#000";
context.fillRect(0, 0, canv.width, canv.height);
context.beginPath();
context.lineWidth = 2;
context.strokeStyle = '#fff';
//Where p1, p2, cp1, cp2 are point objects that has x & y values already defined
context.moveTo(p1.x, p1.y);
context.bezierCurveTo(cp1.x,cp1.y,cp2.x,cp2.y,p2.x,p2.y);
context.stroke();
context.closePath();
// now i have to move p1, p2 ,cp1,cp2
// now here is my problem
}
我知道我需要移动 p1.x+= 一个随机数;
并且对于 cp1 和 cp2 也是一样的,但是 p2 它应该的终点呢沿着相同的轨道走!我怎样才能做到这一点?
谢谢
最佳答案
编辑后的答案
有了你的澄清,我想我现在可以适本地回答这个问题了。
为了让终点沿着起点穿过 Canvas 的路径,您必须存储历史值。在这个例子中,http://jsfiddle.net/mobidevelop/bGgHQ/ ,我使用鼠标移动来填充最后 16 个位置的缓冲区,然后使用它通过遍历 RingBuffer 来形成通过这些点的贝塞尔曲线。
function RingBuffer(length) {
this.length = length;
this.pointer = 0;
this.buffer = [];
}
RingBuffer.prototype.get = function(index) {
if (index < 0) {
index += this.length;
}
return this.buffer[index];
}
RingBuffer.prototype.push = function(value) {
this.buffer[this.pointer] = value;
this.pointer = (this.length + this.pointer +1) % this.length;
}
var c = document.getElementById("myCanvas");
var context =c.getContext("2d");
timer = window.setInterval(draw_line, 30);
function Point(x,y) {
this.x = x;
this.y = y;
}
Point.prototype.translateX = function(x) {
return this.x += x;
};
Point.prototype.translateY = function(y) {
return this.y += y;
};
function draw_line()
{
context.fillStyle = "#000";
context.fillRect(0, 0, c.width, c.height);
var pointer = history.pointer;
context.beginPath();
context.lineWidth = 2;
context.strokeStyle = '#F00';
for (iteration = 0, count = 15; iteration < count; iteration += 3) {
var p1 = history.get(--pointer);
var p2 = history.get(--pointer);
var p3 = history.get(--pointer);
var p4 = history.get(--pointer);
if (p1 && p2 && p3 && p4) {
context.moveTo(p1.x, p1.y);
context.bezierCurveTo(p2.x, p2.y, p3.x, p3.y, p4.x, p4.y);
}
pointer++;
}
context.stroke();
context.closePath();
}
var history = new RingBuffer(16);
var lastGrab = new Date();
c.addEventListener('mousemove', function() {
now = new Date();
if (now - lastGrab > 15) {
history.push(new Point(event.clientX - c.offsetLeft, event.clientY - c.offsetTop));
lastGrab = now;
}
});
之前的回答留在下方,以供历史引用。
我不确定我是否完全理解您要实现的目标,但我认为您需要做的就是将您的所有观点转换为相同的值。这将导致穿过 Canvas 的线保持相同的形状。像这样:
var c = document.getElementById("myCanvas");
var context =c.getContext("2d");
timer = window.setInterval(draw_line, 30);
function Point(x,y) {
this.x = x;
this.y = y;
}
Point.prototype.translateX = function(x) {
return this.x += x;
};
Point.prototype.translateY = function(y) {
return this.y += y;
};
var p1 = new Point(0,0);
var p2 = new Point(100,100);
var cp1 = new Point(15,45);
var cp2 = new Point(85,45);
function draw_line()
{
context.fillStyle = "#000";
context.fillRect(0, 0, c.width, c.height);
context.beginPath();
context.lineWidth = 2;
context.strokeStyle = '#fff';
//Where p1, p2, cp1, cp2 are point objects that has x & y values already defined
context.moveTo(p1.x, p1.y);
context.bezierCurveTo(cp1.x,cp1.y,cp2.x,cp2.y,p2.x,p2.y);
context.stroke();
context.closePath();
p1.translateX(1);
p2.translateX(1);
cp1.translateX(1);
cp2.translateX(1);
if (p1.x > 300) {
p1.translateX(-400);
p2.translateX(-400);
cp1.translateX(-400);
cp2.translateX(-400);
}
}
除非我误解了目标...
关于javascript - Canvas:动画贝塞尔曲线绘制,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/11798053/