您好,我的HTML画布出现问题,当我在画布上从一个接触点连续绘制一个连续的长笔触时,它的效果很好。是否可以先绘制然后停下来再绘制一次,依此类推。即只是用画布绘制多次,而不仅是连续笔划?喜欢能够画脸吗?请参阅下面的代码。感谢任何帮助。
<!DOCTYPE html>
<html>
<head>
<title>Page Title</title>
<style>
canvas { border: 5px solid blue }
</style>
</head>
<body>
<canvas id="c" width="500" height="300"></canvas>
<h1>This is a Heading</h1>
<p>This is a paragraph.</p>
<script>
function midPointBtw(p1, p2) {
return {
x: p1.x + (p2.x - p1.x) / 2,
y: p1.y + (p2.y - p1.y) / 2
};
}
function getPattern() {
return ctx.createPattern(img, 'repeat');
}
var el = document.getElementById('c');
var ctx = el.getContext('2d');
ctx.lineWidth = 50;
ctx.lineJoin = ctx.lineCap = 'round';
var img = new Image;
img.onload = function() {
ctx.strokeStyle = getPattern();
};
img.src = "https://i.postimg.cc/rF2R0GRY/dick2.png";
var isDrawing, points = [];
var getXY = function(e) {
var source = e.touches ? e.touches[0] : e;
return {
x: source.clientX,
y: source.clientY
};
};
var startDrawing = function(e) {
isDrawing = true;
points.push(getXY(e));
event.preventDefault();
};
var keepDrawing = function(e) {
if (!isDrawing) return;
points.push(getXY(e));
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
var p1 = points[0];
var p2 = points[1];
ctx.beginPath();
ctx.moveTo(p1.x, p1.y);
for (var i = 1, len = points.length; i < len; i++) {
var midPoint = midPointBtw(p1, p2);
ctx.quadraticCurveTo(p1.x, p1.y, midPoint.x, midPoint.y);
p1 = points[i];
p2 = points[i + 1];
}
ctx.lineTo(p1.x, p1.y);
ctx.stroke();
event.preventDefault();
};
var stopDrawing = function() {
isDrawing = false;
points = [];
};
el.addEventListener('touchstart', startDrawing);
el.addEventListener('mousedown', startDrawing);
el.addEventListener('touchmove', keepDrawing);
el.addEventListener('mousemove', keepDrawing);
el.addEventListener('touchend', stopDrawing);
el.addEventListener('mouseup', stopDrawing);
function clearCanvas(canvas,ctx) {
ctx.clearRect(0, 0, canvas.width, canvas.height);
}
</script>
<form id ="search">
<input type = "text" name="message" id="user_input">
<input type = "submit" value="Clear Sketchpad" id="clearbutton"
onclick="clearCanvas(canvas,ctx);">
</form>
<p><span id='display'></span></p>
</body>
</html>
答案 0 :(得分:-1)
您正在使用keepDrawing
函数清除画布。尝试删除显示以下内容的行:
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
在该功能中,然后重试。您只需在用户选择按钮时清除画布。