1、去除火狐自带缩放（默认100%大小自动居中），2、可拖拽，3、以鼠标中心缩放，4、限定最小缩放（图片大小和屏幕大小较小值的50%）
当前为
// ==UserScript==
// @name 【自用】JPG
// @namespace Violentmonkey Scripts
// @match http*://*/*.jpg
// @grant none
// @version 2021.07.09
// @author heckles
// @description 1、去除火狐自带缩放（默认100%大小自动居中），2、可拖拽，3、以鼠标中心缩放，4、限定最小缩放（图片大小和屏幕大小较小值的50%）
// ==/UserScript==
//*绑定事件*/
function addEvent(obj, sType, fn) {
if (obj.addEventListener) {
obj.addEventListener(sType, fn, false);
} else {
obj.attachEvent('on' + sType, fn);
}
};
function removeEvent(obj, sType, fn) {
if (obj.removeEventListener) {
obj.removeEventListener(sType, fn, false);
} else {
obj.detachEvent('on' + sType, fn);
}
};
function prEvent(ev) {
var oEvent = ev || window.event;
if (oEvent.preventDefault) {
oEvent.preventDefault();
}
return oEvent;
}
//*添加滑轮事件*/
function addWheelEvent(obj, callback) {
if (window.navigator.userAgent.toLowerCase().indexOf('firefox') != -1) {
addEvent(obj, 'DOMMouseScroll', wheel);
} else {
addEvent(obj, 'mousewheel', wheel);
}
function wheel(ev) {
var oEvent = prEvent(ev),
delta = oEvent.detail ? oEvent.detail > 0 : oEvent.wheelDelta < 0;
callback && callback.call(oEvent, delta);
return false;
}
};
//*页面载入后*/
window.onload = function () {
var oImg = document.getElementById('pic_xx_img'); //【【】【】【】【此处自己改】【】【】【】【】】
/*拖拽功能*/
(function () {
addEvent(oImg, 'mousedown', function (ev) {
var oEvent = prEvent(ev),
oParent = oImg.parentNode,
disX = oEvent.clientX - oImg.offsetLeft,
disY = oEvent.clientY - oImg.offsetTop,
startMove = function (ev) {
if (oParent.setCapture) {
oParent.setCapture();
}
var oEvent = ev || window.event,
l = oEvent.clientX - disX,
t = oEvent.clientY - disY;
oImg.style.left = l + 'px';
oImg.style.top = t + 'px';
oParent.onselectstart = function () {
return false;
}
},
endMove = function (ev) {
if (oParent.releaseCapture) {
oParent.releaseCapture();
}
oParent.onselectstart = null;
removeEvent(oParent, 'mousemove', startMove);
removeEvent(oParent, 'mouseup', endMove);
};
addEvent(oParent, 'mousemove', startMove);
addEvent(oParent, 'mouseup', endMove);
return false;
});
})();
//*以鼠标位置为中心的滑轮放大功能*/
(function () {
addWheelEvent(oImg, function (delta) {
var ratioL = (this.clientX - oImg.offsetLeft) / oImg.offsetWidth,
ratioT = (this.clientY - oImg.offsetTop) / oImg.offsetHeight,
ratioDelta = !delta ? 1 + 0.1 : 1 - 0.1,
w = Math.max(parseInt(oImg.offsetWidth * ratioDelta), Math.min(0.5 * screen.width, 0.5 * img.width)), //!!!这里是自己修改的，限定最小缩放
h = Math.max(parseInt(oImg.offsetHeight * ratioDelta), Math.min(0.5 * screen.height, 0.5 * img.height)), //!!!这里是自己修改的，限定最小缩放
l = Math.round(this.clientX - (w * ratioL)),
t = Math.round(this.clientY - (h * ratioT));
with (oImg.style) {
width = w + 'px';
height = h + 'px';
left = l + 'px';
top = t + 'px';
}
});
})();
};
//==================上面是从网上摘的=====================
var css_s = document.querySelectorAll("head > link:nth-child(3)"); //获取浏览器自带的图片css
css_s[0].href = ""; //删了，要不有冲突
var img_url = document.getElementsByTagName("img")[0].src + "?" + Date.parse(new Date()); //重构地址
var img = new Image(); // 创建对象
img.src = img_url;
//var pichref = window.location.href;//获取当前网址，也就是图片地址
var imgs = document.getElementsByTagName("img");
var img0 = imgs[0]; //获取默认图片
img0.style.cssText = "display:none;height:0px" //隐藏默认图片
var pic_xx = document.createElement("img"); //创建img
document.body.appendChild(pic_xx); //div加到页面最后
pic_xx.setAttribute("Id", "pic_xx_img"); //定ID
pic_xx.src = img_url;
img.onload = function(){// 加载完成执行
var le = 0.5*(window.innerWidth - img.width);
var to = 0.5*(window.innerHeight - img.height);
//alert('width:'+img.width+',height:'+img.height);
pic_xx.style.cssText = "position:absolute;top:"+to+"px;left:"+le+"px;";
};