svg保存为图片下载到本地

今天给大家说一个将svg下载到本地图片的方法，这里我不得不吐槽一下，为啥博客园不可以直接上传本地文件给大家用来直接下载分享呢，好，吐槽到此为止！

这里需要用到一个js文件，名字自己起，内容如下：

(function() {
const out$ = typeof exports != ‘undefined‘ && exports || typeof define != ‘undefined‘ && {} || this || window;
if (typeof define !== ‘undefined‘) define(‘save-svg-as-png‘, [], () => out$);

const xmlns = ‘http://www.w3.org/2000/xmlns/‘;
const doctype = ‘<?xml version="1.0" standalone="no"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd" [<!ENTITY nbsp " ">]>‘;
const urlRegex = /url\(["‘]?(.+?)["‘]?\)/;
const fontFormats = {
woff2: ‘font/woff2‘,
woff: ‘font/woff‘,
otf: ‘application/x-font-opentype‘,
ttf: ‘application/x-font-ttf‘,
eot: ‘application/vnd.ms-fontobject‘,
sfnt: ‘application/font-sfnt‘,
svg: ‘image/svg+xml‘
};

const isElement = obj => obj instanceof HTMLElement || obj instanceof SVGElement;
const requireDomNode = el => {
if (!isElement(el)) throw new Error(`an HTMLElement or SVGElement is required; got ${el}`);
};
const isExternal = url => url && url.lastIndexOf(‘http‘,0) === 0 && url.lastIndexOf(window.location.host) === -1;

const getFontMimeTypeFromUrl = fontUrl => {
const formats = Object.keys(fontFormats)
.filter(extension => fontUrl.indexOf(`.${extension}`) > 0)
.map(extension => fontFormats[extension]);
if (formats) return formats[0];
console.error(`Unknown font format for ${fontUrl}. Fonts may not be working correctly.`);
return ‘application/octet-stream‘;
};

const arrayBufferToBase64 = buffer => {
let binary = ‘‘;
const bytes = new Uint8Array(buffer);
for (let i = 0; i < bytes.byteLength; i++) binary += String.fromCharCode(bytes[i]);
return window.btoa(binary);
}

const getDimension = (el, clone, dim) => {
const v =
(el.viewBox && el.viewBox.baseVal && el.viewBox.baseVal[dim]) ||
(clone.getAttribute(dim) !== null && !clone.getAttribute(dim).match(/%$/) && parseInt(clone.getAttribute(dim))) ||
el.getBoundingClientRect()[dim] ||
parseInt(clone.style[dim]) ||
parseInt(window.getComputedStyle(el).getPropertyValue(dim));
return typeof v === ‘undefined‘ || v === null || isNaN(parseFloat(v)) ? 0 : v;
};

const getDimensions = (el, clone, width, height) => {
if (el.tagName === ‘svg‘) return {
width: width || getDimension(el, clone, ‘width‘),
height: height || getDimension(el, clone, ‘height‘)
};
else if (el.getBBox) {
const {x, y, width, height} = el.getBBox();
return {
width: x + width,
height: y + height
};
}
};

const reEncode = data =>
decodeURIComponent(
encodeURIComponent(data)
.replace(/%([0-9A-F]{2})/g, (match, p1) => {
const c = String.fromCharCode(`0x${p1}`);
return c === ‘%‘ ? ‘%25‘ : c;
})
);

const uriToBlob = uri => {
const byteString = window.atob(uri.split(‘,‘)[1]);
const mimeString = uri.split(‘,‘)[0].split(‘:‘)[1].split(‘;‘)[0]
const buffer = new ArrayBuffer(byteString.length);
const intArray = new Uint8Array(buffer);
for (let i = 0; i < byteString.length; i++) {
intArray[i] = byteString.charCodeAt(i);
}
return new Blob([buffer], {type: mimeString});
};

const query = (el, selector) => {
if (!selector) return;
try {
return el.querySelector(selector) || el.parentNode && el.parentNode.querySelector(selector);
} catch(err) {
console.warn(`Invalid CSS selector "${selector}"`, err);
}
};

const detectCssFont = (rule, href) => {
// Match CSS font-face rules to external links.
// @font-face {
// src: local(‘Abel‘), url(https://fonts.gstatic.com/s/abel/v6/UzN-iejR1VoXU2Oc-7LsbvesZW2xOQ-xsNqO47m55DA.woff2);
// }
const match = rule.cssText.match(urlRegex);
const url = (match && match[1]) || ‘‘;
if (!url || url.match(/^data:/) || url === ‘about:blank‘) return;
const fullUrl =
url.startsWith(‘../‘) ? `${href}/../${url}`
: url.startsWith(‘./‘) ? `${href}/.${url}`
: url;
return {
text: rule.cssText,
format: getFontMimeTypeFromUrl(fullUrl),
url: fullUrl
};
};

const inlineImages = el => Promise.all(
Array.from(el.querySelectorAll(‘image‘)).map(image => {
let href = image.getAttributeNS(‘http://www.w3.org/1999/xlink‘, ‘href‘) || image.getAttribute(‘href‘);
if (!href) return Promise.resolve(null);
if (isExternal(href)) {
href += (href.indexOf(‘?‘) === -1 ? ‘?‘ : ‘&‘) + ‘t=‘ + new Date().valueOf();
}
return new Promise((resolve, reject) => {
const canvas = document.createElement(‘canvas‘);
const img = new Image();
img.crossOrigin = ‘anonymous‘;
img.src = href;
img.onerror = () => reject(new Error(`Could not load ${href}`));
img.onload = () => {
canvas.width = img.width;
canvas.height = img.height;
canvas.getContext(‘2d‘).drawImage(img, 0, 0);
image.setAttributeNS(‘http://www.w3.org/1999/xlink‘, ‘href‘, canvas.toDataURL(‘image/png‘));
resolve(true);
};
});
})
);

const cachedFonts = {};
const inlineFonts = fonts => Promise.all(
fonts.map(font =>
new Promise((resolve, reject) => {
if (cachedFonts[font.url]) return resolve(cachedFonts[font.url]);

const req = new XMLHttpRequest();
req.addEventListener(‘load‘, () => {
// TODO: it may also be worth it to wait until fonts are fully loaded before
// attempting to rasterize them. (e.g. use https://developer.mozilla.org/en-US/docs/Web/API/FontFaceSet)
const fontInBase64 = arrayBufferToBase64(req.response);
const fontUri = font.text.replace(urlRegex, `url("data:${font.format};base64,${fontInBase64}")`)+‘\n‘;
cachedFonts[font.url] = fontUri;
resolve(fontUri);
});
req.addEventListener(‘error‘, e => {
console.warn(`Failed to load font from: ${font.url}`, e);
cachedFonts[font.url] = null;
resolve(null);
});
req.addEventListener(‘abort‘, e => {
console.warn(`Aborted loading font from: ${font.url}`, e);
resolve(null);
});
req.open(‘GET‘, font.url);
req.responseType = ‘arraybuffer‘;
req.send();
})
)
).then(fontCss => fontCss.filter(x => x).join(‘‘));

let cachedRules = null;
const styleSheetRules = () => {
if (cachedRules) return cachedRules;
return cachedRules = Array.from(document.styleSheets).map(sheet => {
try {
return {rules: sheet.cssRules, href: sheet.href};
} catch (e) {
console.warn(`Stylesheet could not be loaded: ${sheet.href}`, e);
return {};
}
});
};

const inlineCss = (el, options) => {
const {
selectorRemap,
modifyStyle,
modifyCss,
fonts
} = options || {};
const generateCss = modifyCss || ((selector, properties) => {
const sel = selectorRemap ? selectorRemap(selector) : selector;
const props = modifyStyle ? modifyStyle(properties) : properties;
return `${sel}{${props}}\n`;
});
const css = [];
const detectFonts = typeof fonts === ‘undefined‘;
const fontList = fonts || [];
styleSheetRules().forEach(({rules, href}) => {
if (!rules) return;
Array.from(rules).forEach(rule => {
if (typeof rule.style != ‘undefined‘) {
if (query(el, rule.selectorText)) css.push(generateCss(rule.selectorText, rule.style.cssText));
else if (detectFonts && rule.cssText.match(/^@font-face/)) {
const font = detectCssFont(rule, href);
if (font) fontList.push(font);
} else css.push(rule.cssText);
}
});
});

return inlineFonts(fontList).then(fontCss => css.join(‘\n‘) + fontCss);
};

out$.prepareSvg = (el, options, done) => {
requireDomNode(el);
const {
left = 0,
top = 0,
width: w,
height: h,
scale = 1,
responsive = false,
} = options || {};

return inlineImages(el).then(() => {
let clone = el.cloneNode(true);
const {backgroundColor = ‘transparent‘} = options || {};
clone.style.backgroundColor = backgroundColor;
const {width, height} = getDimensions(el, clone, w, h);

if (el.tagName !== ‘svg‘) {
if (el.getBBox) {
clone.setAttribute(‘transform‘, clone.getAttribute(‘transform‘).replace(/translate\(.*?\)/, ‘‘));
const svg = document.createElementNS(‘http://www.w3.org/2000/svg‘,‘svg‘);
svg.appendChild(clone);
clone = svg;
} else {
console.error(‘Attempted to render non-SVG element‘, el);
return;
}
}

clone.setAttribute(‘version‘, ‘1.1‘);
clone.setAttribute(‘viewBox‘, [left, top, width, height].join(‘ ‘));
if (!clone.getAttribute(‘xmlns‘)) clone.setAttributeNS(xmlns, ‘xmlns‘, ‘http://www.w3.org/2000/svg‘);
if (!clone.getAttribute(‘xmlns:xlink‘)) clone.setAttributeNS(xmlns, ‘xmlns:xlink‘, ‘http://www.w3.org/1999/xlink‘);

if (responsive) {
clone.removeAttribute(‘width‘);
clone.removeAttribute(‘height‘);
clone.setAttribute(‘preserveAspectRatio‘, ‘xMinYMin meet‘);
} else {
clone.setAttribute(‘width‘, width * scale);
clone.setAttribute(‘height‘, height * scale);
}

Array.from(clone.querySelectorAll(‘foreignObject > *‘)).forEach(foreignObject => {
if (!foreignObject.getAttribute(‘xmlns‘))
foreignObject.setAttributeNS(xmlns, ‘xmlns‘, ‘http://www.w3.org/1999/xhtml‘);
});

return inlineCss(el, options).then(css => {
const style = document.createElement(‘style‘);
style.setAttribute(‘type‘, ‘text/css‘);
style.innerHTML = `<![CDATA[\n${css}\n]]>`;

const defs = document.createElement(‘defs‘);
defs.appendChild(style);
clone.insertBefore(defs, clone.firstChild);

const outer = document.createElement(‘div‘);
outer.appendChild(clone);
const src = outer.innerHTML.replace(/NS\d+:href/gi, ‘xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href‘);

if (typeof done === ‘function‘) done(src, width, height);
else return {src, width, height};
});
});
};

out$.svgAsDataUri = (el, options, done) => {
requireDomNode(el);
const result = out$.prepareSvg(el, options)
.then(({src, width, height}) => {
const svgXml = `data:image/svg+xml;base64,${window.btoa(reEncode(doctype+src))}`;
if (typeof done === ‘function‘) {
done(svgXml, width, height);
}
return svgXml;
});
return result;
};

out$.svgAsPngUri = (el, options, done) => {
requireDomNode(el);
const {
encoderType = ‘image/png‘,
encoderOptions = 0.8,
canvg
} = options || {};

const convertToPng = ({src, width, height}) => {
const canvas = document.createElement(‘canvas‘);
const context = canvas.getContext(‘2d‘);
const pixelRatio = window.devicePixelRatio || 1;

canvas.width = width * pixelRatio;
canvas.height = height * pixelRatio;
canvas.style.width = `${canvas.width}px`;
canvas.style.height = `${canvas.height}px`;
context.setTransform(pixelRatio, 0, 0, pixelRatio, 0, 0);

if (canvg) canvg(canvas, src);
else context.drawImage(src, 0, 0);

let png;
try {
png = canvas.toDataURL(encoderType, encoderOptions);
} catch (e) {
if ((typeof SecurityError !== ‘undefined‘ && e instanceof SecurityError) || e.name === ‘SecurityError‘) {
console.error(‘Rendered SVG images cannot be downloaded in this browser.‘);
return;
} else throw e;
}
if (typeof done === ‘function‘) done(png, canvas.width, canvas.height);
return Promise.resolve(png);
}

if (canvg) return out$.prepareSvg(el, options).then(convertToPng);
else return out$.svgAsDataUri(el, options).then(uri => {
return new Promise((resolve, reject) => {
const image = new Image();
image.onload = () => resolve(convertToPng({
src: image,
width: image.width,
height: image.height
}));
image.onerror = () => {
reject(`There was an error loading the data URI as an image on the following SVG\n${window.atob(uri.slice(26))}Open the following link to see browser‘s diagnosis\n${uri}`);
}
image.src = uri;
})
});
};

out$.download = (name, uri) => {
if (navigator.msSaveOrOpenBlob) navigator.msSaveOrOpenBlob(uriToBlob(uri), name);
else {
const saveLink = document.createElement(‘a‘);
if (‘download‘ in saveLink) {
saveLink.download = name;
saveLink.style.display = ‘none‘;
document.body.appendChild(saveLink);
try {
const blob = uriToBlob(uri);
const url = URL.createObjectURL(blob);
saveLink.href = url;
saveLink.onclick = () => requestAnimationFrame(() => URL.revokeObjectURL(url));
} catch (e) {
console.warn(‘This browser does not support object URLs. Falling back to string URL.‘);
saveLink.href = uri;
}
saveLink.click();
document.body.removeChild(saveLink);
}
else {
window.open(uri, ‘_temp‘, ‘menubar=no,toolbar=no,status=no‘);
}
}
};

out$.saveSvg = (el, name, options) => {
requireDomNode(el);
out$.svgAsDataUri(el, options || {}, uri => out$.download(name, uri));
};

out$.saveSvgAsPng = (el, name, options) => {
requireDomNode(el);
out$.svgAsPngUri(el, options || {}, uri => out$.download(name, uri));
};
})();

看到这里还以为我写了一万多字的博客，太占内存和视觉距离了

然后在自己的svg页面中获取到该svg，我的代码是这个样子的

var canvas = $("#today_chartcontainer svg")[0];
//调用方法转换即可，转换结果就是uri,
svgAsPngUri(canvas, null, function(uri) {

//这里的uri就是要下载到本地的图片地址，是不是很简单啊
$("#tabpanel_items").append(‘<a class="downBtn"; href="‘+uri+‘" download="图片下载">下载图片</a>‘);
});

原文地址：https://www.cnblogs.com/shenwh/p/10528538.html