js实现图片旋转 js滚动鼠标中间对图片放大缩小
程序员文章站
2022-05-26 09:11:54
从开通博客园到今天，有两个多月了。我发现之前没有开通博客记录自己所做的东西，真是后悔啊。
现在一点一点把自己所做的功能以博客的形式记录下来，一方面可以给大家分享，大家一起...
从开通博客园到今天，有两个多月了。我发现之前没有开通博客记录自己所做的东西，真是后悔啊。
现在一点一点把自己所做的功能以博客的形式记录下来，一方面可以给大家分享，大家一起学习，同时自己也从新回顾一下。
这个图片放大，缩小和旋转，我采用canvas画布这个来做的，核心点就在js中去控制鼠标状态及事件。
我先给大家展示一下效果图。
鼠标移到画布范围内就会出现下方的操作栏，每次以90度选择。
1.在引入js的时候一定要注意了，由于在使用画布canvas时，需要等图片加载完成后才可以执行画布里的内容。js要在最后引入。
2.js中要在图片加载完成之后在方法
主要的地方就是这个啦，其它就是js方法了，我就不一一解释了，有js功底的能看懂，如果有地方不懂，或者需要改进的就在下面评论出来，大家一起学习。
下面我就贴出代码了，需要演示项目源码的小伙伴也评论出来，我把演示项目发出来。
这是目录结构，也不需要什么jar包。image下面就是图片啦。
html页面代码
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>insert title here</title>
<script type="text/javascript" src="../js/jquery.js"></script>
<link rel="stylesheet" type="text/css" href="../css/picturecss.css" rel="external nofollow" />
<link >
</head>
<body>
<div id="pandiv">
<img src="../image/3.png" style="display: none;">
<canvas id="canvas" width="700" height="500" style="cursor: default;"> </canvas>
<div id="control" style="display: none;">
<img id="left" src="../image/left1.png" onclick="rateimage(270)">
<img id="right" src="../image/right1.png" onclick="rateimage(90)">
</div>
</div>
<script type="text/javascript" src="../js/picturejs.js"></script>
</body>
</html>
css样式代码
@charset "utf-8";
* {
margin: 0px;
padding: 0px;
}
#pandiv {
width: 700px;
height: 500px;
}
#control {
background: #ccc;
opacity: 0.7;
width: 200px;
height: 30px;
display: none;
padding-top: 5px;
position: absolute;
left: 250px;
top: 450px;
}
#canvas {
border: 1px solid black;
}
#left {
float: left;
display: block;
}
#right {
float: right;
display: block;
}
核心重点js代码：
/**
*
*/
var canvas = document.getelementbyid("canvas");
var pandiv = document.getelementbyid("pandiv");
var cxt = canvas.getcontext("2d");
var control = document.getelementbyid("control");
var imgscale = 1;
var img;
var imgx = 0;
var imgy = 0;
var currentrate = 0;
/**当前的旋转角度*/
var mousedownlocation;
var ismousedown = false;
window.onload = function() {
var bbox = canvas.getboundingclientrect();
var imageurl = $("#pandiv>img").attr("src");
img = new image();
img.src = imageurl;
img.id = "pic";
loadimage();
drawimage();
}
function reloadimage() {
loadimage();
}
function loadimage() {
if (img.width <= canvas.width && img.height <= canvas.height) {
imgx = (canvas.width - img.width * imgscale) / 2
imgy = (canvas.height - img.height * imgscale) / 2;
} else {
var ratio = img.width / img.height;
widthtime = img.width / canvas.width;
heighttime = img.height / canvas.height;
if (widthtime > heighttime) {
img.width = canvas.width;
img.height = canvas.width / ratio;
} else {
img.height = canvas.height;
img.width = canvas.height * ratio;
}
imgx = (canvas.width - img.width * imgscale) / 2
imgy = (canvas.height - img.height * imgscale) / 2
}
}
//var backgroundcolor = ['#223344', '#445566', '#667788', '#778899'];
//var backgroundcolorindex = 0;
function drawimage() {
var bbox = canvas.getboundingclientrect();
//cxt.clearrect(0, 0, canvas.width, canvas.height);
cxt.clearrect(-200, -200, canvas.width * 2, canvas.height * 2);
// cxt.fillstyle = backgroundcolor[backgroundcolorindex++ % backgroundcolor.length];
//cxt.fillrect(0, 0, canvas.width, canvas.height);
cxt.drawimage(img, imgx, imgy, img.width * imgscale, img.height * imgscale);
}
// windowtocanvas此方法用于鼠标所在点的坐标切换到画布上的坐标
function windowtocanvas(canvas, x, y) {
var bbox = canvas.getboundingclientrect();
return {
x : x - bbox.left - (bbox.width - canvas.width) / 2,
y : y - bbox.top - (bbox.height - canvas.height) / 2
};
}
function ispointinimagearea(point) {
return true;
//return (point.x > imgx && point.x < imgx + img.width * imgscale &&
//point.y > imgy && point.y < imgy + img.height * imgscale);
}
function ispointincanvasarea(point) {
return true;
//var bbox = canvas.getboundingclientrect();
//return (point.x > bbox.left && point.x < bbox.right && point.y > bbox.//top && point.y < bbox.bottom);
}
function isdivarea(point) {
return true;
//var bbox =pandiv.getboundingclientrect();
//return (point.x > bbox.left && point.x < bbox.right && point.y > bbox.//top && point.y < bbox.bottom);
}
canvas.onmousewheel = canvas.onwheel = function(event) {
var pos = windowtocanvas(canvas, event.clientx, event.clienty);
event.wheeldelta = event.wheeldelta ? event.wheeldelta
: (event.deltay * (-40));
if (event.wheeldelta > 0) {
//alert("放大");
if (ispointinimagearea(pos)) {
imgscale *= 2;
//imgx = imgx * 2 - pos.x;
// imgy = imgy * 2 - pos.y;
imgx = (canvas.width - img.width * imgscale) / 2
imgy = (canvas.height - img.height * imgscale) / 2
} else {
imgscale *= 2;
//imgx = (canvas.width - img.width * imgscale) / 2;
//imgy = (canvas.height - img.height * imgscale) / 2;
imgx = (canvas.width - img.width * imgscale) / 2
imgy = (canvas.height - img.height * imgscale) / 2
}
} else {
//alert("缩小");
if (ispointinimagearea(pos)) {
imgscale /= 2;
//imgx = imgx * 0.5 + pos.x * 0.5;
// imgy = imgy * 0.5 + pos.y * 0.5;
imgx = (canvas.width - img.width * imgscale) / 2
imgy = (canvas.height - img.height * imgscale) / 2
} else {
imgscale /= 2;
// imgx = (canvas.width - img.width * imgscale) / 2;
// imgy = (canvas.height - img.height * imgscale) / 2;
imgx = (canvas.width - img.width * imgscale) / 2
imgy = (canvas.height - img.height * imgscale) / 2
}
}
drawimage();
return false;
}
/**旋转angle度*/
function rateimage(angle) {
currentrate = (currentrate + angle) % 360;
cxt.clearrect(0, 0, canvas.width, canvas.height);
//cxt.save();
cxt.translate(canvas.width / 2, canvas.height / 2);
cxt.save();
cxt.rotate(angle * math.pi / 180);
cxt.translate(-canvas.width / 2, -canvas.height / 2);
imgscale = 1;
reloadimage();
drawimage();
//cxt.restore();
}
/**鼠标按下*/
pandiv.onmousedown = function(event) {
mousedownlocation = windowtocanvas(canvas, event.clientx, event.clienty);
if (ispointinimagearea(mousedownlocation)) {
ismousedown = true;
document.title = 'mouse down';
}
}
/**鼠标弹起*/
document.body.onmouseup = function() {
ismousedown = false;
canvas.style.cursor = "default";
document.title = 'mouse up';
}
/**鼠标移动*/
pandiv.onmousemove = function(event) {
if (ismousedown) {
canvas.style.cursor = "move";
var newmouselocation = windowtocanvas(canvas, event.clientx,
event.clienty);
if (isdivarea({
x : event.clientx,
y : event.clienty
})) {
var x = newmouselocation.x - mousedownlocation.x;
var y = newmouselocation.y - mousedownlocation.y;
mousedownlocation = newmouselocation;
/**根据角度，计算图片偏移*/
if (0 == currentrate) {
imgx += x;
imgy += y;
} else if (90 == currentrate) {
imgx += y;
imgy -= x;
} else if (180 == currentrate) {
imgx -= x;
imgy -= y;
} else if (270 == currentrate) {
imgx -= y;
imgy += x;
}
} else {
/** 鼠标移动至画布范围外，置鼠标弹起 */
ismousedown = false;
canvas.style.cursor = "default";
document.title = 'mouse up';
}
drawimage();
}
}
pandiv.onmouseover = function() {
//alert("1");
control.style.display = "block";
}
canvas.onmouseout = function() {
//alert("1");
control.style.display = "none";
}
这就是实现这个图片旋转，放大，缩小的演示代码。
由于这几天在做一个切换图片的功能，点击上一页，下一页实现图片切换，这个功能以及快全部实现了，到时候我搭建一个框架的演示项目，来给大家展示图片切换上一张，下一张，也包括旋转，放大缩小功能。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。