sharp包
https://www.npmjs.com/package/sharp
sharp文档链接
https://sharp.pixelplumbing.com/en/stable/
buffer与stream相互转换
http://derpturkey.com/buffer-to-stream-in-node/
text转svg包
https://www.npmjs.com/package/text-to-svg
代码示例
// 跨平台、高性能、无运行时依赖
const sharp = require('sharp');
const fs = require('fs');
const textToSvg = require('text-to-svg');
const basePicture = `${__dirname}/static/云雾缭绕.png`;
// 流转Buffer缓存
function streamToBuffer(stream) {
return new Promise((resolve, reject) => {
const bufferList = []
stream.on('data', data => {
// 每一个data都是一个Buffer对象
bufferList.push(data)
})
stream.on('error', err => {
reject()
})
stream.on('end', () => {
resolve(Buffer.concat(bufferList))
})
})
}
/**
* 1、toFile
* @param {String} basePicture 源文件路径
* @param {String} newFilePath 新文件路径
*/
function writeTofile(basePicture, newFilePath) {
sharp(basePicture)
.rotate(20) // 旋转
.resize(500, 500) //缩放
.toFile(newFilePath)
}
// writeTofile(basePicture, `${__dirname}/static/云雾缭绕1.png`);
/**
* 2、读取图片buffer
* @param {String} basePicture 源文件路径
*/
function readFileBuffer(basePicture) {
sharp(basePicture)
.toBuffer()
.then(data => {
console.log(data)
})
.catch(err => {
console.log(err)
})
}
// readFileBuffer(basePicture);
/**
* 3、对文件流进行处理
* @param {String} basePicture 源文件路径
*/
function dealWithStream(basePicture) {
// 读取文件流
const readableStream = fs.createReadStream(basePicture)
// 对流数据进行处理
const transformer = sharp().resize({
width: 200,
height: 200,
fit: sharp.fit.cover,
position: sharp.strategy.entropy
})
// 将文件读取到的流数据写入transformer进行处理
readableStream.pipe(transformer)
// 将可写流转换为buffer写入本地文件
streamToBuffer(transformer).then(function(newPicBuffer) {
fs.writeFile(`${__dirname}/static/云雾缭绕2.png`, newPicBuffer, function(
err
) {
if (err) {
console.log(err)
}
console.log('done')
})
})
}
// dealWithStream(basePicture);
/**
* 4、将文件的转为JPEG，并对JPEG文件进行处理
* @param {String} basePicture 源文件路径
*/
function dealWithBuffer(basePicture) {
sharp(basePicture)
.resize(300, 300, {
fit: sharp.fit.inside,
withoutEnlargement: true
})
.toFormat('jpeg')
.toBuffer()
.then(function(outputBuffer) {
fs.writeFile(`${__dirname}/static/云雾缭绕3.jpeg`, outputBuffer, function(
err
) {
if (err) {
console.log(err)
}
console.log('done')
})
})
}
// dealWithBuffer(basePicture)
/**
* 5、添加水印
* @param {String} basePicture 原图路径
* @param {String} watermarkPicture 水印图片路径
* @param {String} newFilePath 输出图片路径
*/
function addWatermark(basePicture, watermarkPicture, newFilePath) {
sharp(basePicture)
.rotate(180) // 旋转180度
.composite([
{
input: watermarkPicture,
top: 10,
left: 10
}
]) // 在左上坐标（10， 10）位置添加水印图片
.withMetadata() // 在输出图像中包含来自输入图像的所有元数据(EXIF、XMP、IPTC)。
.webp({
quality: 90
}) //使用这些WebP选项来输出图像。
.toFile(newFilePath)
.catch(err => {
console.log(err)
})
// 注意水印图片尺寸不能大于原图
}
// addWatermark(
// basePicture,
// `${__dirname}/static/水印.png`,
// `${__dirname}/static/云雾缭绕4.png`
// )
/**
* 添加文字，类似添加水印
* @param {String} basePicture 原图路径
* @param {Object} font 字体设置
* @param {String} newFilePath 输出图片路径
* @param {String} text 待粘贴文字
* @param {Number} font.fontSize 文字大小
* @param {String} font.color 文字颜色
* @param {Number} font.left 文字距图片左边缘距离
* @param {Number} font.top 文字距图片上边缘距离
*/
function addText(basePicture, font, newFilePath) {
const { fontSize, text, color, left, top } = font;
// 同步加载文字转SVG的库
const textToSvgSync = textToSvg.loadSync();
// 设置文字属性
const attributes = {
fill: color
};
const options = {
fontSize,
anchor: 'top',
attributes
};
// 文字转svg，svg转buffer
const svgTextBuffer = Buffer.from(textToSvgSync.getSVG(text, options));
// 添加文字
sharp(basePicture)
// .rotate(180) // 旋转180度
.composite([
{
input: svgTextBuffer,
top,
left
}
]) // 在左上坐标（10， 10）位置添加文字
.withMetadata() // 在输出图像中包含来自输入图像的所有元数据(EXIF、XMP、IPTC)。
.webp({
quality: 90
}) //使用这些WebP选项来输出图像。
.toFile(newFilePath)
.catch(err => {
console.log(err)
});
}
addText(
basePicture,
{
fontSize: 50,
text: '洋溢洋溢洋溢',
color: 'yellow',
left: 100,
top: 100
},
`${__dirname}/static/云雾缭绕5.png`
);
resize参数
// 摘抄于sharp库
interface ResizeOptions {
/** Alternative means of specifying width. If both are present this take priority. */
width?: number;
/** Alternative means of specifying height. If both are present this take priority. */
height?: number;
/** How the image should be resized to fit both provided dimensions, one of cover, contain, fill, inside or outside. (optional, default 'cover') */
fit?: keyof FitEnum;
/** Position, gravity or strategy to use when fit is cover or contain. (optional, default 'centre') */
position?: number | string;
/** Background colour when using a fit of contain, parsed by the color module, defaults to black without transparency. (optional, default {r:0,g:0,b:0,alpha:1}) */
background?: Color;
/** The kernel to use for image reduction. (optional, default 'lanczos3') */
kernel?: keyof KernelEnum;
/** Do not enlarge if the width or height are already less than the specified dimensions, equivalent to GraphicsMagick's > geometry option. (optional, default false) */
withoutEnlargement?: boolean;
/** Take greater advantage of the JPEG and WebP shrink-on-load feature, which can lead to a slight moiré pattern on some images. (optional, default true) */
fastShrinkOnLoad?: boolean;
}
合成水印示例
image.png