问题
我想用图像而不是canvas目的。这意味着您必须先将要添加的内容添加到画布并作为画布的一部分，然后才能添加它。这些图像实际上是网站的一部分，因此不需要做一些复杂的事情。我在这里找到的这段代码仅适用于对象而不是实际元素的情况。顺便说一句我正在使用FabricJS http://fabricjs.com/只是为了让您知道我没有使用默认的 HTML5 画布内容。
至于任何可能在不使用我当前代码的情况下工作的替代方案。请务必将其发布在下面的评论或答案中。我真的很想知道你们的想法。
Summary
基本上我希望能够在画布上拖放图像，同时保留鼠标光标位置。例如，如果我拖动图像并且光标位于 x: 50 y: 75 处，它会将图像拖放到该确切位置。就像我找到的代码所做的那样。但就像问题所述，代码使用一个对象将其拖到画布上，然后克隆它。我希望仅使用普通的旧元素来实现此功能。例如：<img>.
代码 -
JsFiddle http://jsfiddle.net/ssk7833/qy5p6a0g/14/
window.canvas = new fabric.Canvas('fabriccanvas');
var edgedetection = 8; //pixels to snap
canvas.selection = false;
window.addEventListener('resize', resizeCanvas, false);
function resizeCanvas() {
canvas.setHeight(window.innerHeight);
canvas.setWidth(window.innerWidth);
canvas.renderAll();
}
// resize on init
resizeCanvas();
//Initialize Everything
init();
function init(top, left, width, height, fill) {
var bg = new fabric.Rect({
left: 0,
top: 0,
fill: "#eee",
width: window.innerWidth,
height: 75,
lockRotation: true,
maxHeight: document.getElementById("fabriccanvas").height,
maxWidth: document.getElementById("fabriccanvas").width,
selectable: false,
});
var squareBtn = new fabric.Rect({
top: 10,
left: 18,
width: 40,
height: 40,
fill: '#af3',
lockRotation: true,
originX: 'left',
originY: 'top',
cornerSize: 15,
hasRotatingPoint: false,
perPixelTargetFind: true,
});
var circleBtn = new fabric.Circle({
radius: 20,
fill: '#f55',
top: 10,
left: 105,
});
var triangleBtn = new fabric.Triangle({
width: 40,
height: 35,
fill: 'blue',
top: 15,
left: 190,
});
var sqrText = new fabric.IText("Add Square", {
fontFamily: 'Indie Flower',
fontSize: 14,
fontWeight: 'bold',
left: 6,
top: 50,
selectable: false,
});
var cirText = new fabric.IText("Add Circle", {
fontFamily: 'Indie Flower',
fontSize: 14,
fontWeight: 'bold',
left: 95,
top: 50,
selectable: false,
});
var triText = new fabric.IText("Add Triangle", {
fontFamily: 'Indie Flower',
fontSize: 14,
fontWeight: 'bold',
left: 175,
top: 50,
selectable: false,
});
var shadow = {
color: 'rgba(0,0,0,0.6)',
blur: 3,
offsetX: 0,
offsetY: 2,
opacity: 0.6,
fillShadow: true,
strokeShadow: true
};
window.canvas.add(bg);
bg.setShadow(shadow);
window.canvas.add(squareBtn);
window.canvas.add(circleBtn);
window.canvas.add(triangleBtn);
window.canvas.add(sqrText);
window.canvas.add(cirText);
window.canvas.add(triText);
canvas.forEachObject(function (e) {
e.hasControls = e.hasBorders = false; //remove borders/controls
});
function draggable(object) {
object.on('mousedown', function() {
var temp = this.clone();
temp.set({
hasControls: false,
hasBorders: false,
});
canvas.add(temp);
draggable(temp);
});
object.on('mouseup', function() {
// Remove an event handler
this.off('mousedown');
// Comment this will let the clone object able to be removed by drag it to menu bar
// this.off('mouseup');
// Remove the object if its position is in menu bar
if(this.top<=75) {
canvas.remove(this);
}
});
}
draggable(squareBtn);
draggable(circleBtn);
draggable(triangleBtn);
this.canvas.on('object:moving', function (e) {
var obj = e.target;
obj.setCoords(); //Sets corner position coordinates based on current angle, width and height
canvas.forEachObject(function (targ) {
activeObject = canvas.getActiveObject();
if (targ === activeObject) return;
if (Math.abs(activeObject.oCoords.tr.x - targ.oCoords.tl.x) < edgedetection) {
activeObject.left = targ.left - activeObject.currentWidth;
}
if (Math.abs(activeObject.oCoords.tl.x - targ.oCoords.tr.x) < edgedetection) {
activeObject.left = targ.left + targ.currentWidth;
}
if (Math.abs(activeObject.oCoords.br.y - targ.oCoords.tr.y) < edgedetection) {
activeObject.top = targ.top - activeObject.currentHeight;
}
if (Math.abs(targ.oCoords.br.y - activeObject.oCoords.tr.y) < edgedetection) {
activeObject.top = targ.top + targ.currentHeight;
}
if (activeObject.intersectsWithObject(targ) && targ.intersectsWithObject(activeObject)) {
} else {
targ.strokeWidth = 0;
targ.stroke = false;
}
if (!activeObject.intersectsWithObject(targ)) {
activeObject.strokeWidth = 0;
activeObject.stroke = false;
activeObject === targ
}
});
});
}
我找到了更多代码，但没有解决我的问题：
var canvas = new fabric.Canvas('c');
canvas.on("after:render", function(){canvas.calcOffset();});
var started = false;
var x = 0;
var y = 0;
var width = 0;
var height = 0;
canvas.on('mouse:down', function(options) {
//console.log(options.e.clientX, options.e.clientY);
x = options.e.clientX;
y = options.e.clientY;
canvas.on('mouse:up', function(options) {
width = options.e.clientX - x;
height = options.e.clientY - y;
var square = new fabric.Rect({
width: width,
height: height,
left: x + width/2 - canvas._offset.left,
top: y + height/2 - canvas._offset.top,
fill: 'red',
opacity: .2
});
canvas.add(square);
canvas.off('mouse:up');
$('#list').append('<p>Test</p>');
});
});
此代码向画布添加一个矩形。但问题是这并没有达到我想要的效果，基本上，如前所述，我希望能够拖动一个img元素，然后无论您将该图像拖动到画布上的哪个位置，它都会将其精确地放置在该位置。
CREDITS
Fabric JS：鼠标按下时复制/粘贴对象 https://stackoverflow.com/questions/28183763/fabric-js-copy-paste-object-on-mouse-down
Fabric.js 偏移解决方案 https://stackoverflow.com/questions/17328675/fabric-js-offset-solution/17328990?noredirect=1#comment51942569_17328990
