画布绘图大小需要修复

canvas drawing size fix needed

本文关键字：布绘图 绘图      更新时间：2023-11-29

在我的画布上，当你改变大小时，我有它，所以你可以从1到100，但我有它所以它在5秒内上升，但当你达到1并再次上升时，它会上升到6，然后再次上升，然后上升到11，依此类推。

给你http://jsfiddle.net/daniel9000/tsaytohj/2/

这是我的java脚本

function processData(c1, c2) {
var cv1 = document.getElementById(c1).value;
var cv2 = document.getElementById(c2).value;
alert(cv1 + "'n" + cv2);
}
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
var radius = 10;
var dragging = false;
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
context.lineWidth = radius * 2;
var putPoint = function (e) {
if (dragging) {
var bounds = canvas.getBoundingClientRect();
var mouseX = e.clientX + bounds.left;
var mouseY = e.clientY - bounds.top;
var mouseX = e.clientX + bounds.left - 0;
context.lineTo(mouseX, mouseY)
context.strokeStyle = document.getElementById('color1').value;
context.stroke();
context.beginPath();
context.arc(mouseX, mouseY, radius, 0, Math.PI * 2);
context.fillStyle = document.getElementById('color1').value;
context.fill();
context.beginPath();
context.moveTo(mouseX, mouseY);
}
}
var engage = function (e) {
dragging = true;
putPoint(e);
}
var disengage = function () {
dragging = false;
context.beginPath();
}
canvas.addEventListener('mousedown', engage);
canvas.addEventListener('mousemove', putPoint);
canvas.addEventListener('mouseup', disengage);
var setRadius = function (newRadius) {
if (newRadius < minRad) newRadius = minRad;
else if (newRadius > maxRad) newRadius = maxRad;
radius = newRadius;
context.lineWidth = radius * 2;
radSpan.innerHTML = radius;
}
var minRad = 1,
maxRad = 100,
defaultRad = 20,
interval = 5,
radSpan = document.getElementById('radval'),
decRad = document.getElementById('decrad'),
incRad = document.getElementById('incrad');
decRad.addEventListener('click', function () {
setRadius(radius - interval);
});
incRad.addEventListener('click', function () {
setRadius(radius + interval);
});
setRadius(defaultRad);
var button = document.getElementById('btn-download');
button.addEventListener('click', function (e) {
var dataURL = canvas.toDataURL('image/png');
button.href = dataURL;
});

这真的很简单。我建议这样做：

decRad.addEventListener('click', function () {
    setRadius(radius - interval);
});
incRad.addEventListener('click', function () {
    setRadius(radius < interval ? interval : radius + interval);
});

这是因为您设置了minRad=1，它不在5的倍数序列中，可能是为了避免半径为零。所以当你加5的时候，你得到的是6而不是5。您有几种可能的解决方案：

  • 设置minRad=0
  • 只允许最小半径为5，即minRad=5

  • 如果不是上述任一项，则必须使用不按顺序的最小值进行补偿，方法是将radius = newRadius;替换为：

    radius = newRadius;
if( radius == 6) radius = 5;
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