js实现在图片上画矩形框
2019独角兽企业重金招聘Python工程师标准>>> 
文章图片
JS组件：
@author Darkness
@version 1.0
@date 2010-08-18
Function.prototype.bind = function(obj){
var _method = this;
return function(){
_method.apply(obj, arguments);
}
}DrawRectangle = function(id, onMouseUp, className){
this.IMG = document.getElementById(id);
this.isDraw = false;
this.isMouseUp = true;
this.index = 0;
this.currentDrawRectangle = null;
this.className = className;
this.RectangleDivs = [];
this.debug = false;
this._onMouseUp = onMouseUp;
this.bindListener();
}DrawRectangle.prototype = {
bindListener: function(){this.IMG.onmousemove = this.dragSize.bind(this);
this.IMG.onmouseup = this.onMouseUp.bind(this);
this.IMG.onmouseout = this.onMouseOut.bind(this);
this.IMG.onmouseover = this.onMouseOver.bind(this);
this.IMG.onmousedown = this.drawLayer.bind(this);
this.IMG.onmouseup = this.onMouseUp.bind(this);
},
drawLayer: function(){
this.IMG.setCapture(true);
this.isDraw = true;
this.ismouseup = false;
this.index++;
var pos = this.getSourcePos();
var x = event.offsetX;
var y = event.offsetY;
var top = y + pos.top - 2;
var left = x + pos.left - 2;
var d = document.createElement("div");
document.body.appendChild(d);
d.style.border = "1px solid #ff0000";
d.style.width = 0;
d.style.height = 0;
d.style.overflow = "hidden";
d.style.position = "absolute";
d.style.left = left;
d.style.top = top;
if(this.className) {
d.className = this.className;
}
d.id = "draw" + this.index;
if (this.debug) {
//d.innerHTML = "x:" + x + ",y:" + y + ". img_x:" + img_x + ",img_y:" + img_y + ".";
}this.currentDrawRectangle = d;
this.RectangleDivs[this.index] = {
left: left,
top: top,
el: d
};
},
getSourcePos: function(){
return this.getAbsolutePosition(this.IMG);
},
dragSize: function(){
if (this.isDraw) {
if (event.srcElement.tagName != "IMG")
return;
var pos = this.getSourcePos();
var img_x = pos.top;
var img_y = pos.left;
var x = event.offsetX;
var y = event.offsetY;
var drawW = (x + img_x) - this.RectangleDivs[this.index].left;
var drawH = (y + img_y) - this.RectangleDivs[this.index].top;
this.currentDrawRectangle.style.width = drawW > 0 ? drawW : -drawW;
this.currentDrawRectangle.style.height = drawH > 0 ? drawH : -drawH;
if (drawW < 0) {
this.currentDrawRectangle.style.left = x + img_x;
}
if (drawH < 0) {
this.currentDrawRectangle.style.top = y + img_y;
}if (this.debug) {
this.currentDrawRectangle.innerHTML = "x:" + x + ",y:" + y +
". img_x:" +
img_x +
",img_y:" +
img_y +
". drawW:" +
drawW +
",drawH:" +
drawH +
".Dleft[i]:" +
this.RectangleDivs[this.index].left +
",Dtop[i]:" +
this.RectangleDivs[this.index].top +
"src:" +
event.srcElement.tagName +
".";
}}
else {
return false;
}
},stopDraw: function(){
this.isDraw = false;
},onMouseOut: function(){
if (!this.isMouseUp) {
this.isDraw = false;
}
},onMouseUp: function(){
this.isDraw = false;
this.isMouseUp = true;
this.IMG.releaseCapture();
if(this._onMouseUp) {
this._onMouseUp.call(this, this.currentDrawRectangle);
}
},onMouseOver: function(){
if (!this.isMouseUp) {
this.isDraw = true;
}
},getAbsolutePosition: function(obj){
var t = obj.offsetTop;
var l = obj.offsetLeft;
var w = obj.offsetWidth;
var h = obj.offsetHeight;
while (obj = obj.offsetParent) {
t += obj.offsetTop;
l += obj.offsetLeft;
}return {
top: t,
left: l,
width: w,
height: h
}
}
};
测试页面：
DrawRectangle - 锐客网 
文章图片
@version 1.1
@description 采用div替换原来的img作为画布，修复不兼容其他浏览器bug
@author Darkness
@date 2012-07-27
问题：1.0版本中采用IMG.setCapture(true); 方式在图片上实现鼠标拖动等事件监听，该方式在最新的ie9下行不通，也不兼容其他浏览器
改进：采用一个div作为画布替换原来的img，将img作为其背景并删除原来的img，然后监听div上的鼠标拖动等事件达到原来同样的效果，此方式兼容其他浏览器
代码：
DrawRectangle = function(id, onMouseUp, className){
document.oncontextmenu=function() {
return true;
};
this.IMG = document.getElementById(id);
var masker = document.createElement("div");
masker.id = "mask_" + id;
var position = this.getAbsolutePosition(this.IMG);
masker.style.width = position.width + "px";
masker.style.height = position.height + "px";
masker.style.left = position.left;
masker.style.top = position.top;
masker.style["background-image"] = "url("+this.IMG.src+")";
masker.className = "imgmasker";
this.masker = masker;
this.IMG.parentNode.appendChild(masker);
this.IMG.parentNode.removeChild(this.IMG);
this.isDraw = false;
this.isMouseUp = true;
this.index = 0;
this.currentDrawRectangle = null;
this.className = className;
this.RectangleDivs = [];
this.debug = true;
this._onMouseUp = onMouseUp;
this.bindListener();
};
DrawRectangle.prototype = {
bindListener: function(){this.masker.onmousemove = this.dragSize.bind(this);
this.masker.onmouseup = this.onMouseUp.bind(this);
this.masker.onmouseout = this.onMouseOut.bind(this);
this.masker.onmouseover = this.onMouseOver.bind(this);
this.masker.onmousedown = this.drawLayer.bind(this);
this.masker.onmouseup = this.onMouseUp.bind(this);
},
drawLayer: function(){
//this.IMG.setCapture(true);
this.isDraw = true;
this.ismouseup = false;
this.index++;
var pos = this.getSourcePos();
var x = event.offsetX;
var y = event.offsetY;
var top = y + pos.top - 2;
var left = x + pos.left - 2;
var d = document.createElement("div");
// document.body.appendChild(d);
this.masker.appendChild(d);
d.style.border = "1px solid #ff0000";
d.style.width = 0;
d.style.height = 0;
d.style.overflow = "hidden";
d.style.position = "absolute";
d.style.left = left + "px";
d.style.top = top + "px";
d.style.opacity = 0.5;
d.style["z-index"] = 2;
if(this.className) {
d.className = this.className;
}
d.id = "draw" + this.index;
if (this.debug) {
d.innerHTML = "x:" + x + ",y:" + y + "..";
}this.currentDrawRectangle = d;
this.RectangleDivs[this.index] = {
left: left,
top: top,
el: d
};
},
getSourcePos: function(){
return this.getAbsolutePosition(this.masker);
},
dragSize: function(){
if (this.isDraw) {
if (!(event.srcElement.tagName.toLowerCase() == "div" && event.srcElement.className == "imgmasker"))
return;
var pos = this.getSourcePos();
var img_x = pos.top;
var img_y = pos.left;
var x = event.offsetX;
var y = event.offsetY;
var drawW = (x + img_x) - this.RectangleDivs[this.index].left;
var drawH = (y + img_y) - this.RectangleDivs[this.index].top;
this.currentDrawRectangle.style.width = (drawW > 0 ? drawW : -drawW) + "px";
this.currentDrawRectangle.style.height = (drawH > 0 ? drawH : -drawH) + "px";
if (drawW < 0) {
this.currentDrawRectangle.style.left = (x + img_x) + "px";
}
if (drawH < 0) {
this.currentDrawRectangle.style.top = (y + img_y) + "px";
}if (this.debug) {
this.currentDrawRectangle.innerHTML = "x:" + x + ",y:" + y +
". img_x:" +
img_x +
",img_y:" +
img_y +
". drawW:" +
drawW +
",drawH:" +
drawH +
".Dleft[i]:" +
this.RectangleDivs[this.index].left +
",Dtop[i]:" +
this.RectangleDivs[this.index].top +
"src:" +
event.srcElement.tagName +
",this.isDraw: " + this.isDraw +
",this.isMouseUp: " + this.isMouseUp +
".";
}}
else {
return false;
}
},stopDraw: function(){
this.isDraw = false;
},onMouseOut: function(){
if (!this.isMouseUp) {
this.isDraw = false;
}
},onMouseUp: function(){
this.isDraw = false;
this.isMouseUp = true;
//this.IMG.releaseCapture();
if(this._onMouseUp) {
this._onMouseUp.call(this, this.currentDrawRectangle);
}
},onMouseOver: function(){
if (!this.isMouseUp) {
this.isDraw = true;
}
},getAbsolutePosition: function(obj){
var t = obj.offsetTop;
var l = obj.offsetLeft;
var w = obj.offsetWidth;
var h = obj.offsetHeight;
while (obj = obj.offsetParent) {
t += obj.offsetTop;
l += obj.offsetLeft;
}return {
top: t,
left: l,
width: w,
height: h
};
}
};
测试：
DrawRectangle - 锐客网
文章图片
效果图：
文章图片
【js实现在图片上画矩形框】转载于:https://my.oschina.net/darkness/blog/510218
