我正在允许用户在图像上绘制矩形。同时,用户应该能够在任何时候调整或移动任何一个矩形。
在一些帮助下,我已经能够绘制矩形,但是我无法实现其调整和移动部分。
被绘制的矩形不会重叠,而在调整和移动时也必须进行验证。
我正在使用JavaScript和jQuery。
这是我目前所做的演示:
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var canvasOffset = $("#canvas").offset();
var offsetX = canvasOffset.left;
var offsetY = canvasOffset.top;
var startX;
var startY;
var isDown = false;
ctx.strokeStyle = "lightgray";
ctx.lineWidth = 3;
function handleMouseDown(e) {
mouseX = parseInt(e.clientX - offsetX);
mouseY = parseInt(e.clientY - offsetY);
// Put your mousedown stuff here
startX = mouseX;
startY = mouseY;
isDown = true;
}
function handleMouseUp(e) {
mouseX = parseInt(e.clientX - offsetX);
mouseY = parseInt(e.clientY - offsetY);
$("#uplog").html("Up: " + mouseX + " / " + mouseY);
// Put your mouseup stuff here
isDown = false;
}
function handleMouseMove(e) {
mouseX = parseInt(e.clientX - offsetX);
mouseY = parseInt(e.clientY - offsetY);
// Put your mousemove stuff here
if (!isDown) {
return;
}
ctx.clearRect(0, 0, canvas.width, canvas.height);
drawRectangle(mouseX, mouseY);
}
function drawRectangle(mouseX, mouseY) {
var width = mouseX - startX;
var height = mouseY - startY;
ctx.beginPath();
ctx.rect(startX, startY, width, height);
ctx.stroke();
}
$("#canvas").mousedown(function (e) {
handleMouseDown(e);
});
$("#canvas").mousemove(function (e) {
handleMouseMove(e);
});
$("#canvas").mouseup(function (e) {
handleMouseUp(e);
});
由于时间紧迫,我现在无法弄清楚如何完成这项任务。