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我是JavaScript新用户!JS帆布:lineTo()
如何为当前xy坐标分配一个变量,以便我可以使用相对位置来绘制直线?试图用键盘进行蚀刻草图。上,下,左,右箭头键...与JS,CSS和HTML。
谢谢!
window.addEventListener("keydown", keyd);
function keyd(event) {
var etchMain = document.getElementById('etchMain');
var etchContext = etchMain.getContext('2d');
var key = event.keyCode;
**var etchContextPositionX;
var etchContextPositionY;**
if (key == 37) {
// left arrow
if (etchMain.toDataURL() == document.getElementById('blank').toDataURL()) {
etchContext.beginPath();
etchContext.moveTo(etchMain.width/2, etchMain.height/2);
// arrow specific drawing goes here
}
else {
}
}
if (key == 38) {
// up arrow
if (etchMain.toDataURL() == document.getElementById('blank').toDataURL()) {
etchContext.beginPath();
etchContext.moveTo(etchMain.width/2, etchMain.height/2);
// arrow specific drawing goes here
}
else {
}
}
if (key == 39) {
// right arrow
if (etchMain.toDataURL() == document.getElementById('blank').toDataURL()) {
etchContext.beginPath();
etchContext.moveTo(etchMain.width/2, etchMain.height/2);
// arrow specific drawing goes here
}
else {
}
}
if (key == 39) {
// down arrow
if (etchMain.toDataURL() == document.getElementById('blank').toDataURL()) {
etchContext.beginPath();
etchContext.moveTo(etchMain.width/2, etchMain.height/2);
// arrow specific drawing goes here
}
else {
}
}
}
function clearCanvas() {
var etchMain = document.getElementById('etchMain');
var etchContext = etchMain.getContext('2d');
etchContext.clearRect(0, 0, etchMain.width, etchMain.height);
}