1. 前言
不知道各位前端小伙伴蓝湖使用的多不多，反正我是经常在用，ui将原型图设计好后上传至蓝湖，前端开发人员就可以开始静态页面的的编写了。对于页面细节看的不是很清楚可以使用滚轮缩放后再拖拽查看，还是很方便的。于是就花了点时间研究了一下。今天分享给大家。
2. 实现
HTML
html
<div class="imgBox">
<img style="width: 150px; height: 150px; padding: 10px" src="../../../images/HTTP工作原理.jpg" class="img-responsive" />
<img style="width: 150px; height: 150px; padding: 10px" src="../../../images/HTTP报文结构.jpg" class="img-responsive" />
</div>
<div id="outerdiv" style="
position: fixed;
top: 0;
left: 0;
background: rgba(0, 0, 0, 0.7);
z-index: 2;
width: 100%;
height: 100%;
display: none;
">
<img id="bigimg" src="" />
</div>js
拖拽查看图片逻辑
java
function imgDrag() {
// 绑定 鼠标按下事件
image.addEventListener("pointerdown", pointerdown);
// 绑定 鼠标移动事件
image.addEventListener("pointermove", pointermove);
image.addEventListener("pointerup", function (e) {
if (isPointerdown) {
isPointerdown = false;
}
});
image.addEventListener("pointercancel", function (e) {
if (isPointerdown) {
isPointerdown = false;
}
});
}
function pointerdown(e) {
isPointerdown = true;
console.log(e.pointerId)
// 说明：Element.setPointerCapture()将特定元素指定为未来指针事件的捕获目标。指针的后续事件将以捕获元素为目标，直到捕获被释放。可以理解为：在窗口不是全屏情况下，我在拖动放大图片时即使鼠标移出可窗口之外，此时事件还是捕获在该放大图片上。
image.setPointerCapture(e.pointerId);
lastPointermove = {
x: e.clientX,
y: e.clientY,
};
}
function pointermove(e) {
if (isPointerdown) {
const current1 = {
x: e.clientX,
y: e.clientY,
};
diff.x = current1.x - lastPointermove.x;
diff.y = current1.y - lastPointermove.y;
lastPointermove = {
x: current1.x,
y: current1.y,
};
x += diff.x;
y += diff.y;
image.style.transform = `translate3d(${x}px, ${y}px, 0) scale(${initScale})`;
}
e.preventDefault();
}滚轮缩放逻辑
javascript
function handleStopWheel(e) {
let itemSizeChange = 1.1; //每一次滚动放大的倍数
if (e.target.id == "bigimg") {
// 说明：e.dataY如果大于0则表示鼠标向下滚动，反之则向上滚动，这里设计为向上滚动为缩小，向下滚动为放大
if (e.deltaY < 0) {
itemSizeChange = 1 / 1.1;
}
let _initScale = initScale * itemSizeChange;
// 说明：在超过或低于临界值时，虽然让initScale等于maxZoom或minreduce，但是在后续的判断中放大图片的最终倍数并没有达到maxZoom或minreduce，而是跳过。
if (_initScale > maxZoom) {
initScale = maxZoom;
} else if (_initScale < minreduce) {
initScale = minreduce;
} else {
initScale = _initScale;
}
const origin = {
x: (itemSizeChange - 1) * imgWidth * 0.5,
y: (itemSizeChange - 1) * imgHeight * 0.5,
};
// 计算偏移量
if (_initScale < maxZoom && _initScale > minreduce) {
x -= (itemSizeChange - 1) * (e.clientX - x) - origin.x;
y -= (itemSizeChange - 1) * (e.clientY - y) - origin.y;
e.target.style.transform = `translate3d(${x}px, ${y}px, 0) scale(${initScale})`;
}
}
// 阻止默认事件
e.preventDefault();
}js全部代码
html
<script>
/**
* 实现图片点击放大、拖拽、滚轴滚动焦点缩放功能，相关参数、函数声明
*/
let imgWidth, imgHeight; // 图片点击放大初始尺寸参数
let maxZoom = 4; //最大缩放倍数
let minreduce = 0.5; // 最小缩放倍数
let initScale = 1; //滚动缩放初始倍数，并不是图片点击放大的倍数
let isPointerdown = false; //鼠标按下的标识
//记录鼠标按下坐标和按下移动时坐标
let lastPointermove = {
x: 0,
y: 0,
};
//移动过程从上一个坐标到下一个坐标之间的差值
let diff = {
x: 0,
y: 0,
};
//图片放大后左上角的坐标，主要结合diff参数用于鼠标焦点缩放时图片偏移坐标
let x = 0;
let y = 0;
// 记录节点
const allImg = document.querySelectorAll(".imgBox img");
const outerdiv = document.querySelector("#outerdiv");
const image = outerdiv.querySelector("#bigimg");
window.onload = function () {
allImg.forEach((item) => {
item.addEventListener("click", (e) => {
const that = e.target;
image.style.transform = "scale(1)";
//图片放大展示函数调用
imgShow(that);
// 监听鼠标滚动事件
window.addEventListener("wheel", handleStopWheel, {
passive: false,
});
// 拖转事件调用
imgDrag();
});
});
};
function imgShow(that) {
let src = that.getAttribute("src");
image.setAttribute("src", src);
// 设置尺寸和调整比例
let windowW = document.documentElement.clientWidth;
let windowH = document.documentElement.clientHeight;
let realWidth = image.naturalWidth; //获取图片的原始宽度
let realHeight = image.naturalHeight; //获取图片的原始高度
let outsideScale = 0.8;
let belowScale = 1.4;
let realRatio = realWidth / realHeight;
let windowRatio = windowW / windowH;
// 说明：下面是我自己的一些判断逻辑，大致意思就是图片的真实尺寸大于屏幕尺寸则使用屏幕尺寸，如果小于屏幕尺寸就使用自己本身的尺寸；并根据大于或者小于的比例对图片的尺寸进一步调整。coder可以根据自己的要求进行修改。
if (realRatio >= windowRatio) {
if (realWidth > windowW) {
imgWidth = windowH * outsideScale;
imgHeight = (imgWidth / realWidth) * realHeight;
} else {
if (realWidth * belowScale < windowW) {
imgWidth = realWidth * (belowScale - 0.2);
imgHeight = (imgWidth / realWidth) * realHeight;
} else {
imgWidth = realWidth;
imgHeight = realHeight;
}
}
} else {
if (realHeight > windowH) {
imgHeight = windowH * outsideScale;
imgWidth = (imgHeight / realHeight) * realWidth;
} else {
if (realHeight * belowScale < windowW) {
imgHeight = realHeight * (belowScale - 0.2);
imgWidth = (imgHeight / realHeight) * realWidth;
} else {
imgWidth = realWidth;
imgHeight = realHeight;
}
}
}
//设置放大图片的尺寸、偏移量并展示
image.style.width = imgWidth + "px";
image.style.height = imgHeight + "px";
x = (windowW - imgWidth) * 0.5;
y = (windowH - imgHeight) * 0.5;
image.style.transform = `translate3d(${x}px, ${y}px, 0)`;
outerdiv.style.display = "block";
// 点击蒙版及外面区域放大图片关闭
outerdiv.onclick = () => {
outerdiv.style.display = "none";
initScale = 1;
window.removeEventListener("wheel", handleStopWheel);
};
// 阻止事件冒泡
image.onclick = (e) => {
e.stopPropagation();
};
}
function handleStopWheel(e) {
let itemSizeChange = 1.1; //每一次滚动放大的倍数
if (e.target.id == "bigimg") {
// 说明：e.dataY如果大于0则表示鼠标向下滚动，反之则向上滚动，这里设计为向上滚动为缩小，向下滚动为放大
if (e.deltaY < 0) {
itemSizeChange = 1 / 1.1;
}
let _initScale = initScale * itemSizeChange;
// 说明：在超过或低于临界值时，虽然让initScale等于maxZoom或minreduce，但是在后续的判断中放大图片的最终倍数并没有达到maxZoom或minreduce，而是跳过。
if (_initScale > maxZoom) {
initScale = maxZoom;
} else if (_initScale < minreduce) {
initScale = minreduce;
} else {
initScale = _initScale;
}
const origin = {
x: (itemSizeChange - 1) * imgWidth * 0.5,
y: (itemSizeChange - 1) * imgHeight * 0.5,
};
// 计算偏移量
if (_initScale < maxZoom && _initScale > minreduce) {
x -= (itemSizeChange - 1) * (e.clientX - x) - origin.x;
y -= (itemSizeChange - 1) * (e.clientY - y) - origin.y;
e.target.style.transform = `translate3d(${x}px, ${y}px, 0) scale(${initScale})`;
}
}
// 阻止默认事件
e.preventDefault();
}
function imgDrag() {
// 绑定 鼠标按下事件
image.addEventListener("pointerdown", pointerdown);
// 绑定 鼠标移动事件
image.addEventListener("pointermove", pointermove);
image.addEventListener("pointerup", function (e) {
if (isPointerdown) {
isPointerdown = false;
}
});
image.addEventListener("pointercancel", function (e) {
if (isPointerdown) {
isPointerdown = false;
}
});
}
function pointerdown(e) {
isPointerdown = true;
console.log(e.pointerId)
// 说明：Element.setPointerCapture()将特定元素指定为未来指针事件的捕获目标。指针的后续事件将以捕获元素为目标，直到捕获被释放。可以理解为：在窗口不是全屏情况下，我在拖动放大图片时即使鼠标移出可窗口之外，此时事件还是捕获在该放大图片上。
image.setPointerCapture(e.pointerId);
lastPointermove = {
x: e.clientX,
y: e.clientY,
};
}
function pointermove(e) {
if (isPointerdown) {
const current1 = {
x: e.clientX,
y: e.clientY,
};
diff.x = current1.x - lastPointermove.x;
diff.y = current1.y - lastPointermove.y;
lastPointermove = {
x: current1.x,
y: current1.y,
};
x += diff.x;
y += diff.y;
image.style.transform = `translate3d(${x}px, ${y}px, 0) scale(${initScale})`;
}
e.preventDefault();
}
</script>