這是一個用於在畫布上繪製線條的JavaScript代碼。點擊執行Javascript文件
var canvas,
context,
dragging = false,
dragStartLocation,
snapshot;
function getCanvasCoordinates(event) {
var x = event.clientX - canvas.getBoundingClientRect().left,
y = event.clientY - canvas.getBoundingClientRect().top;
return {x: x, y: y};
}
function takeSnapshot() {
snapshot = context.getImageData(0, 0, canvas.width, canvas.height);
}
function restoreSnapshot() {
context.putImageData(snapshot, 0, 0);
}
function drawLine(position) {
context.beginPath();
context.moveTo(dragStartLocation.x, dragStartLocation.y);
context.lineTo(position.x, position.y);
context.stroke();
}
function dragStart(event) {
dragging = true;
dragStartLocation = getCanvasCoordinates(event);
takeSnapshot();
}
function drag(event) {
var position;
if (dragging === true) {
restoreSnapshot();
position = getCanvasCoordinates(event);
drawLine(position);
}
}
function dragStop(event) {
dragging = false;
restoreSnapshot();
var position = getCanvasCoordinates(event);
drawLine(position);
}
function init() {
canvas = document.getElementById("canvas");
context = canvas.getContext('2d');
context.strokeStyle = 'black';
context.lineWidth = 6;
context.lineCap = 'round';
canvas.addEventListener('mousedown', dragStart, false);
canvas.addEventListener('mousemove', drag, false);
canvas.addEventListener('mouseup', dragStop, false);
}
如何添加一個按鈕,以便當按鈕點擊代碼執行?我怎樣才能做到這一點?一個例子如下,以澄清事情
<input type="BUTTON" value="Exit" onclick="execute the javascript file to draw line" >
有你搜尋它在谷歌 – Mahi
這正是你只是寫「爲例」 – Hammerbot
@El_Matella當行按鈕獲取激活我不能使用免費的繪圖工具。我怎麼能避免這種情況? –