Step 1:- Create an index.html
<!DOCTYPE html>
<html lang="en" dir="ltr">
<head>
<meta charset="utf-8">
<title>Image Resizer JavaScript</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
<link
href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css"
rel="stylesheet"
integrity="sha384-EVSTQN3/azprG1Anm3QDgpJLIm9Nao0Yz1ztcQTwFspd3yD65VohhpuuCOmLASjC"
crossorigin="anonymous"
>
<link rel="stylesheet" href="style.css">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<script src="script.js" defer></script>
</head>
<body>
<div class="wrapper">
<div class="upload-box">
<input type="file" accept="image/*" hidden>
<img src="upload-icon.svg" alt="">
<p>Browse File to Upload</p>
</div>
<div class="content">
<div class="row sizes">
<div class="column width">
<label>Width</label>
<input type="number">
</div>
<div class="column height">
<label>Height</label>
<input type="number">
</div>
</div>
<div class="row checkboxes">
<div class="column ratio">
<input type="checkbox" id="ratio" checked>
<label for="ratio">Lock aspect ratio</label>
</div>
<div class="column quality">
<input type="checkbox" id="quality">
<label for="quality">Reduce quality</label>
</div>
</div>
<button class="download-btn">Download Image</button>
</div>
</div>
</body>
</html>
Step 2:- Create a script.js
const uploadBox = document.querySelector(".upload-box"),
previewImg = uploadBox.querySelector("img"),
fileInput = uploadBox.querySelector("input"),
widthInput = document.querySelector(".width input"),
heightInput = document.querySelector(".height input"),
ratioInput = document.querySelector(".ratio input"),
qualityInput = document.querySelector(".quality input"),
downloadBtn = document.querySelector(".download-btn");
let ogImageRatio;
const loadFile = (e) => {
const file = e.target.files[0]; // getting first user selected file
if(!file) return; // return if user hasn't selected any file
previewImg.src = URL.createObjectURL(file); // passing selected file url to preview img src
previewImg.addEventListener("load", () => { // once img loaded
widthInput.value = previewImg.naturalWidth;
heightInput.value = previewImg.naturalHeight;
ogImageRatio = previewImg.naturalWidth / previewImg.naturalHeight;
document.querySelector(".wrapper").classList.add("active");
});
}
widthInput.addEventListener("keyup", () => {
// getting height according to the ratio checkbox status
const height = ratioInput.checked ? widthInput.value / ogImageRatio : heightInput.value;
heightInput.value = Math.floor(height);
});
heightInput.addEventListener("keyup", () => {
// getting width according to the ratio checkbox status
const width = ratioInput.checked ? heightInput.value * ogImageRatio : widthInput.value;
widthInput.value = Math.floor(width);
});
const resizeAndDownload = () => {
const canvas = document.createElement("canvas");
const a = document.createElement("a");
const ctx = canvas.getContext("2d");
// if quality checkbox is checked, pass 0.5 to imgQuality else pass 1.0
// 1.0 is 100% quality where 0.5 is 50% of total. you can pass from 0.1 - 1.0
const imgQuality = qualityInput.checked ? 0.5 : 1.0;
// setting canvas height & width according to the input values
canvas.width = widthInput.value;
canvas.height = heightInput.value;
// drawing user selected image onto the canvas
ctx.drawImage(previewImg, 0, 0, canvas.width, canvas.height);
// passing canvas data url as href value of <a> element
a.href = canvas.toDataURL("image/jpeg", imgQuality);
a.download = new Date().getTime(); // passing current time as download value
a.click(); // clicking <a> element so the file download
}
downloadBtn.addEventListener("click", resizeAndDownload);
fileInput.addEventListener("change", loadFile);
uploadBox.addEventListener("click", () => fileInput.click());Output:-
Also, Click on Reduce quality for more size reduction.
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