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Editor to share with you vue how to upload pictures to add watermarks, I believe that most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

1. Encapsulate and add watermark method

/ * add watermark * @ param {blob} file * @ param {string} el * @ returns {Promise} * / export async function addWaterMarker (file, el ='# markImg') {return new Promise (async (resolve) Reject) = > {try {/ / first compress and rotate the picture file = await compressor (file) / / convert the file blob to the picture let img = await blobToImg (file) / / create the canvas canvas let canvas = document.createElement ('canvas') canvas.width = img.naturalWidth canvas.height = img.naturalHeight let ctx = canvas.getContext (' 2d') / / Populate the uploaded image ctx.drawImage (img) 0,0, canvas.width, canvas.height) / / generate a watermark image const markEle = document.querySelector (el) const markWidth = markEle.clientWidth const scale = canvas.width * 0.25 / markWidth / / first scale the watermark and then convert it to an image markEle.style.transform = `scale (${scale}) `watermark = await htmlToCanvas (markEle) / / filled watermark ctx.drawImage (markImg) Canvas.width-markImg.width-15 * scale, canvas.height-markImg.height-15 * scale, markImg.width, markImg.height) / / convert canvas to blob canvas.toBlob (blob = > resolve (blob))} catch (error) {reject (error)}})} function blobToImg (blob) {return new Promise ((resolve, reject) = > {let reader = new FileReader () reader.addEventListener ('load') () = > {let img = new Image () img.src = reader.result img.addEventListener ('load', () = > resolve (img)}) reader.readAsDataURL (blob)})} export function htmlToCanvas (el, backgroundColor =' rgba') {return new Promise (async (resolve, reject) = > {try {const markImg = await html2canvas (el, {scale: 2) / / the default value window.devicePixelRatio is not used here Need to be consistent with mobile allowTaint: false, / / allow contamination of useCORS: true BackgroundColor / / 'transparent' / / background color}) resolve (markImg)} catch (error) {reject (error)})} / * compress and rotate images * @ param {blob} file * @ param {number} quality compression ratio * @ param {number} maxWidth * @ returns {Promise} * / export function compressor (file, quality = 0.6 MaxWidth) {return new Promise (resolve = > {new Compressor (file, {maxWidth, quality, success: resolve, error (err) {console.log (err.message)}

2. Use in the project

Import {getTaskDetail, userExecute, submitFlow, rejectFlow,} from'@ / api/myTask';import {uploadOSS} from'@ / utils/oss';import {parseTime, addWaterMarker} from'@ / utils';import {ImagePreview} from 'vant';import Compressor from' compressorjs';const fileExtensions = ['xlsx',' xls', 'docx',' doc', 'pdf']; const quality = 0.2 / / Image compression quality export default {methods: {/ / pre-upload async handleBeforeImgUpload (img, detail) {if (! img) {return} return new Promise (async (resolve, reject) = > {if (Array.isArray (img)) {if (img.length > 5) {this.$toast ('upload up to 5 copies at a time, please upload them in batches!') Reject ()} let blobs = [] for (const file of img) {/ / if the image is greater than 512k, compress if (file.size > 512x 1024 & & file.type.includes ('image/')) {file = await this.compressor (file)} / / add watermark first. Let blob = await addWaterMarker (file) blob.name = file.name blobs.push (blob)} resolve (blobs)} else {/ / images greater than 512k compress if (img.size > 512k * 1024 & & img.type.includes ('image/')) {img = await this.compressor ( Img)} const blob = await addWaterMarker (img) blob.name = img.name resolve (blob)})} / / async handleAfterImgUpload (img, detail) {try {$loading.show () if (Array.isArray (img)) {img.forEach (async ({file}, index) = > {if (! file.name | |! file.type.includes ('image/')) {this.currentItem.imgUpload.splice (detail.index + index) after upload 1) this.$toast ('upload failed You can only upload photos!') / / the return in if (index = img.length-1) {$loading.hide ()} return / / forEach is equivalent to continue} if (file.size > 1024 * 1024 * 10) {this.currentItem.imgUpload.splice (detail.index + index, 1) this.$toast ('file is too large A single file cannot exceed 10MB') / / upload completed if (index = img.length-1) {$loading.hide ()} return} try {const {fileName, url} = await uploadOSS (file) this.currentItem.answer.push ({url) })} catch (error) {this.currentItem.imgUpload.splice (detail.index + index, 1) this.$toast ('upload failed Please try again later!) Console.error (error)} / / upload completed if (index = img.length-1) {$loading.hide ()})} else {if (! img.file.type.includes ('image')) {this.currentItem.imgUpload.splice (detail.index) 1) $loading.hide () this.$toast ('upload failed You can only upload photos!') Return} if (img.file.size > = 1024 * 1024 * 10) {this.currentItem.imgUpload.splice (detail.index, 1) $loading.hide () this.$toast ('the file is too large to exceed 10MB') If return} / / is greater than 512k, compress let file = img.file const {fileName, url} = await uploadOSS (file) this.currentItem.answer.push ({url,}) $loading.hide ()}} catch (error) {this.currentItem.imgUpload.splice (detail.index) 1) $loading.hide () this.$toast ('upload failed Please try again later!) Console.error (error)}

3. The effect is as follows

The above is all the contents of the article "how to upload pictures and add watermarks in vue". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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