Javascript HTML5画布,带手绘线条
我是HTML5画布的新手,目前正在尝试为孩子们制作一个简单的画线项目。我将背景图像插入画布,并尝试提出一种徒手画线的方法,但没有结果。有人能帮我修复下面的代码吗?谢谢大家Javascript HTML5画布,带手绘线条,javascript,html,canvas,html5-canvas,Javascript,Html,Canvas,Html5 Canvas,我是HTML5画布的新手,目前正在尝试为孩子们制作一个简单的画线项目。我将背景图像插入画布,并尝试提出一种徒手画线的方法,但没有结果。有人能帮我修复下面的代码吗?谢谢大家 <!DOCTYPE HTML> <html> <script type="text/javascript"> var canvas, ctx, flag = false, prevX = 0, currX = 0, prevY
<!DOCTYPE HTML>
<html>
<script type="text/javascript">
var canvas, ctx, flag = false,
prevX = 0,
currX = 0,
prevY = 0,
currY = 0,
dot_flag = false;
var x = "black",
y = 2;
function init() {
canvas = document.getElementById('can');
ctx = canvas.getContext("2d");
w = canvas.width;
h = canvas.height;
canvas.addEventListener("mousemove", function (e) {
findxy('move', e)
}, false);
canvas.addEventListener("mousedown", function (e) {
findxy('down', e)
}, false);
canvas.addEventListener("mouseup", function (e) {
findxy('up', e)
}, false);
canvas.addEventListener("mouseout", function (e) {
findxy('out', e)
}, false);
}
function color(obj) {
switch (obj.id) {
case "green":
x = "green";
break;
case "blue":
x = "blue";
break;
case "red":
x = "red";
break;
case "yellow":
x = "yellow";
break;
case "orange":
x = "orange";
break;
case "black":
x = "black";
break;
case "white":
x = "white";
break;
}
if (x == "white") y = 14;
else y = 2;
}
function draw() {
ctx.beginPath();
ctx.moveTo(prevX, prevY);
ctx.lineTo(currX, currY);
ctx.strokeStyle = x;
ctx.lineWidth = y;
ctx.stroke();
ctx.closePath();
}
function erase() {
var m = confirm("Want to clear");
if (m) {
ctx.clearRect(0, 0, w, h);
document.getElementById("canvasimg").style.display = "none";
}
}
function save() {
document.getElementById("canvasimg").style.border = "2px solid";
var dataURL = canvas.toDataURL();
document.getElementById("canvasimg").src = dataURL;
document.getElementById("canvasimg").style.display = "inline";
}
function findxy(res, e) {
if (res == 'down') {
prevX = currX;
prevY = currY;
currX = e.clientX - canvas.offsetLeft;
currY = e.clientY - canvas.offsetTop;
flag = true;
dot_flag = true;
if (dot_flag) {
ctx.beginPath();
ctx.fillStyle = x;
ctx.fillRect(currX, currY, 2, 2);
ctx.closePath();
dot_flag = false;
}
}
if (res == 'up' || res == "out") {
flag = false;
}
if (res == 'move') {
if (flag) {
prevX = currX;
prevY = currY;
currX = e.clientX - canvas.offsetLeft;
currY = e.clientY - canvas.offsetTop;
draw();
}
}
}
</script>
<body onload="init()" style="background-image: src=c:/WebProgram/Pictures/test1.png;">
<canvas id="can" width="520" height="700" style="position:absolute;top:10%;left:10%;border:2px solid;"></canvas>
<div style="position:absolute;top:12%;left:43%;">Choose Color</div>
<div style="position:absolute;top:15%;left:45%;width:10px;height:10px;background:green;" id="green" onclick="color(this)"></div>
<div style="position:absolute;top:15%;left:46%;width:10px;height:10px;background:blue;" id="blue" onclick="color(this)"></div>
<div style="position:absolute;top:15%;left:47%;width:10px;height:10px;background:red;" id="red" onclick="color(this)"></div>
<div style="position:absolute;top:17%;left:45%;width:10px;height:10px;background:yellow;" id="yellow" onclick="color(this)"></div>
<div style="position:absolute;top:17%;left:46%;width:10px;height:10px;background:orange;" id="orange" onclick="color(this)"></div>
<div style="position:absolute;top:17%;left:47%;width:10px;height:10px;background:black;" id="black" onclick="color(this)"></div>
<div style="position:absolute;top:20%;left:43%;">Eraser</div>
<div style="position:absolute;top:22%;left:45%;width:15px;height:15px;background:white;border:2px solid;" id="white" onclick="color(this)"></div>
<img id="canvasimg" style="position:absolute;top:10%;left:52%;" style="display:none;">
<input type="button" value="save" id="btn" size="30" onclick="save()" style="position:absolute;top:5%;left:10%;">
<input type="button" value="clear" id="clr" size="23" onclick="erase()" style="position:absolute;top:5%;left:15%;">
</body>
</html>
变量画布,ctx,标志=false,
prevX=0,
currX=0,
prevY=0,
咖喱=0,
dot_标志=假;
var x=“黑色”,
y=2;
函数init(){
canvas=document.getElementById('can');
ctx=canvas.getContext(“2d”);
w=画布宽度;
h=画布高度;
canvas.addEventListener(“mousemove”,函数(e){
findxy('move',e)
},假);
canvas.addEventListener(“鼠标向下”,函数(e){
findxy('down',e)
},假);
canvas.addEventListener(“mouseup”,函数(e){
findxy('up',e)
},假);
canvas.addEventListener(“mouseout”,函数(e){
findxy('out',e)
},假);
}
功能颜色(obj){
开关(对象id){
案例“绿色”:
x=“绿色”;
打破
案例“蓝色”:
x=“蓝色”;
打破
案例“红色”:
x=“红色”;
打破
案例“黄色”:
x=“黄色”;
打破
案例“橙色”:
x=“橙色”;
打破
案例“黑色”:
x=“黑色”;
打破
“白色”案例:
x=“白色”;
打破
}
如果(x=“白色”)y=14;
否则y=2;
}
函数绘图(){
ctx.beginPath();
ctx.moveTo(prevX,prevY);
ctx.lineTo(咖喱,咖喱);
ctx.strokeStyle=x;
ctx.lineWidth=y;
ctx.stroke();
ctx.closePath();
}
函数擦除(){
var m=确认(“想要清算”);
如果(m){
ctx.clearRect(0,0,w,h);
document.getElementById(“canvasimg”).style.display=“无”;
}
}
函数save(){
document.getElementById(“canvasimg”).style.border=“2px solid”;
var dataURL=canvas.toDataURL();
document.getElementById(“canvasimg”).src=dataURL;
document.getElementById(“canvasimg”).style.display=“inline”;
}
函数findxy(res,e){
如果(res=='down'){
prevX=currX;
prevY=咖喱;
currX=e.clientX-canvas.offsetLeft;
currY=e.clientY-canvas.offsetTop;
flag=true;
dot_flag=true;
if(dot_标志){
ctx.beginPath();
ctx.fillStyle=x;
ctx.fillRect(currX,currY,2,2);
ctx.closePath();
dot_标志=假;
}
}
如果(res==“向上”| res==“向外”){
flag=false;
}
如果(res=='move'){
国际单项体育联合会(旗){
prevX=currX;
prevY=咖喱;
currX=e.clientX-canvas.offsetLeft;
currY=e.clientY-canvas.offsetTop;
draw();
}
}
}
选择颜色
橡皮擦
仔细想想,这个过程其实很简单:
- 首先,单击鼠标时获取鼠标点(x和y坐标)(确保仅在单击鼠标时获取这些点)
- 然后在点之间画线。这也应该很容易。(请记住,这些线应该只在鼠标按下时绘制,并且应该从用户按下鼠标或触摸屏幕的第一个点开始。几乎每次有输入时都应该如此)
- 现在保存您需要的图形
- 使用canvas'
函数将图像转换为数据URLtoDataURL()
- 然后使用将dataURL转换为Blob
- 使用
创建指向blob的链接URL.createObjectURL(blob)
- 创建一个
- 使用canvas'
好极了!希望这有帮助,很抱歉这么懒,没有给出实际代码来支持这个答案。仔细想想,这个过程其实很简单:
- 首先,单击鼠标时获取鼠标点(x和y坐标)(确保仅在单击鼠标时获取这些点)
- 然后在点之间画线。这也应该很容易。(请记住,这些线应该只在鼠标按下时绘制,并且应该从用户按下鼠标或触摸屏幕的第一个点开始。几乎每次有输入时都应该如此)
- 现在保存您需要的图形
- 使用canvas'
函数将图像转换为数据URLtoDataURL()
- 然后使用将dataURL转换为Blob
- 使用
创建指向blob的链接URL.createObjectURL(blob)
- 创建一个
- 使用canvas'
function createCanvas(width, height) {
const c = document.createElement("canvas");
c.width = width;
c.height = height;
c.ctx = c.getContext("2d");
return c;
}
const drawing = createCanvas(512,512);
ctx.drawImage(drawing,0,0);
// a point object creates point from x,y coords or object that has x,y
const point = (x, y = x.y + ((x = x.x) * 0)) => ({ x, y });
// function to add a point to the line
function addPoint(x, y) { this.points.push(point(x, y)); }
// draw a line on context ctx and adds offset.x, offset.y
function drawLine(ctx, offset) {
ctx.strokeStyle = this.color;
ctx.lineWidth = this.width;
ctx.lineJoin = "round";
ctx.lineCap = "round";
ctx.beginPath();
var i = 0;
while (i < this.points.length) {
const p = this.points[i++];
ctx.lineTo(p.x + offset.x, p.y + offset.y);
}
ctx.stroke();
}
// creates a new line object
function createLine(color, width) {
return {
points: [], // the points making up the line
color, // colour of the line
width, // width of the line
add: addPoint, // function to add a point
draw: drawLine, // function to draw the whole line
};
}