如何修改此JavaScript代码以防止无限放大
How to modify this JavaScript code to prevent unlimited zoom in
我写了下面的html代码来显示全屏图像。由于我的图像有时非常大，我希望能够放大并看到细节。我在这里找到了这个JavaScript代码http://www.jacklmoore.com/wheelzoom/。它工作得很好，但我想防止无限放大。我需要它受到图像大小的限制。我如何修改代码才能做到这一点？谢谢
HTML
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Zoom</title>
<style>
html, body {
background:#333333;
height: 100%;
margin: 0;
padding: 0;
}
#image {
padding: 0;
display: block;
margin: 0 auto;
max-height: 100%;
max-width: 100%;
}
</style>
</head>
<body>
<img class='zoom' src='MyImage.jpg' id='image'/>
<script src="wheelzoom.js"></script>
<script>
wheelzoom(document.querySelector('img.zoom'));
</script>
</body>
</html>
JavaScript
/*!
Wheelzoom 3.0.4
license: MIT
http://www.jacklmoore.com/wheelzoom
*/
window.wheelzoom = (function(){
var defaults = {
zoom: 0.10
};
var canvas = document.createElement('canvas');
var main = function(img, options){
if (!img || !img.nodeName || img.nodeName !== 'IMG') { return; }
var settings = {};
var width;
var height;
var bgWidth;
var bgHeight;
var bgPosX;
var bgPosY;
var previousEvent;
var cachedDataUrl;
function setSrcToBackground(img) {
img.style.backgroundImage = 'url("'+img.src+'")';
img.style.backgroundRepeat = 'no-repeat';
canvas.width = img.naturalWidth;
canvas.height = img.naturalHeight;
cachedDataUrl = canvas.toDataURL();
img.src = cachedDataUrl;
}
function updateBgStyle() {
if (bgPosX > 0) {
bgPosX = 0;
} else if (bgPosX < width - bgWidth) {
bgPosX = width - bgWidth;
}
if (bgPosY > 0) {
bgPosY = 0;
} else if (bgPosY < height - bgHeight) {
bgPosY = height - bgHeight;
}
img.style.backgroundSize = bgWidth+'px '+bgHeight+'px';
img.style.backgroundPosition = bgPosX+'px '+bgPosY+'px';
}
function reset() {
bgWidth = width;
bgHeight = height;
bgPosX = bgPosY = 0;
updateBgStyle();
}
function onwheel(e) {
var deltaY = 0;
e.preventDefault();
if (e.deltaY) { // FireFox 17+ (IE9+, Chrome 31+?)
deltaY = e.deltaY;
} else if (e.wheelDelta) {
deltaY = -e.wheelDelta;
}
// As far as I know, there is no good cross-browser way to get the cursor position relative to the event target.
// We have to calculate the target element's position relative to the document, and subtrack that from the
// cursor's position relative to the document.
var rect = img.getBoundingClientRect();
var offsetX = e.pageX - rect.left - window.pageXOffset;
var offsetY = e.pageY - rect.top - window.pageYOffset;
// Record the offset between the bg edge and cursor:
var bgCursorX = offsetX - bgPosX;
var bgCursorY = offsetY - bgPosY;
// Use the previous offset to get the percent offset between the bg edge and cursor:
var bgRatioX = bgCursorX/bgWidth;
var bgRatioY = bgCursorY/bgHeight;
// Update the bg size:
if (deltaY < 0) {
bgWidth += bgWidth*settings.zoom;
bgHeight += bgHeight*settings.zoom;
} else {
bgWidth -= bgWidth*settings.zoom;
bgHeight -= bgHeight*settings.zoom;
}
// Take the percent offset and apply it to the new size:
bgPosX = offsetX - (bgWidth * bgRatioX);
bgPosY = offsetY - (bgHeight * bgRatioY);
// Prevent zooming out beyond the starting size
if (bgWidth <= width || bgHeight <= height) {
reset();
} else {
updateBgStyle();
}
}
function drag(e) {
e.preventDefault();
bgPosX += (e.pageX - previousEvent.pageX);
bgPosY += (e.pageY - previousEvent.pageY);
previousEvent = e;
updateBgStyle();
}
function removeDrag() {
document.removeEventListener('mouseup', removeDrag);
document.removeEventListener('mousemove', drag);
}
// Make the background draggable
function draggable(e) {
e.preventDefault();
previousEvent = e;
document.addEventListener('mousemove', drag);
document.addEventListener('mouseup', removeDrag);
}
function load() {
if (img.src === cachedDataUrl) return;
var computedStyle = window.getComputedStyle(img, null);
width = parseInt(computedStyle.width, 10);
height = parseInt(computedStyle.height, 10);
bgWidth = width;
bgHeight = height;
bgPosX = 0;
bgPosY = 0;
setSrcToBackground(img);
img.style.backgroundSize = width+'px '+height+'px';
img.style.backgroundPosition = '0 0';
img.addEventListener('wheelzoom.reset', reset);
img.addEventListener('wheel', onwheel);
img.addEventListener('mousedown', draggable);
}
var destroy = function (originalProperties) {
img.removeEventListener('wheelzoom.destroy', destroy);
img.removeEventListener('wheelzoom.reset', reset);
img.removeEventListener('load', load);
img.removeEventListener('mouseup', removeDrag);
img.removeEventListener('mousemove', drag);
img.removeEventListener('mousedown', draggable);
img.removeEventListener('wheel', onwheel);
img.style.backgroundImage = originalProperties.backgroundImage;
img.style.backgroundRepeat = originalProperties.backgroundRepeat;
img.src = originalProperties.src;
}.bind(null, {
backgroundImage: img.style.backgroundImage,
backgroundRepeat: img.style.backgroundRepeat,
src: img.src
});
img.addEventListener('wheelzoom.destroy', destroy);
options = options || {};
Object.keys(defaults).forEach(function(key){
settings[key] = options[key] !== undefined ? options[key] : defaults[key];
});
if (img.complete) {
load();
}
img.addEventListener('load', load);
};
// Do nothing in IE8
if (typeof window.getComputedStyle !== 'function') {
return function(elements) {
return elements;
};
} else {
return function(elements, options) {
if (elements && elements.length) {
Array.prototype.forEach.call(elements, main, options);
} else if (elements && elements.nodeName) {
main(elements, options);
}
return elements;
};
}
}());
查找
if (deltaY < 0) {
bgWidth += bgWidth*settings.zoom;
bgHeight += bgHeight*settings.zoom;
并更改为
if (deltaY < 0) {
if(bgWidth < canvas.width){
bgWidth += bgWidth*settings.zoom;
bgHeight += bgHeight*settings.zoom;}
您还应该引用html头标记
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