How to Crop an Image in JavaScript?

Last Updated : 08 Nov, 2024

To crop an image in JavaScript, you can use the <canvas> element to manipulate the image's dimensions and crop it to a specified area. This approach is flexible and works entirely in the browser without needing external libraries. Here's a step-by-step example demonstrating how to crop an image using JavaScript:

Example for Cropping an Image with Canvas

HTML

<!DOCTYPE html> <html lang="en"> <head>   <meta charset="UTF-8">   <meta name="viewport" content="width=device-width, initial-scale=1.0">   <title>Crop Image with JavaScript</title> </head> <body>   <input type="file" id="fileInput" accept="image/*">   <canvas id="canvas" style="border: 1px solid black;"></canvas>   <script>     const fileInput = document.getElementById('fileInput');     const canvas = document.getElementById('canvas');     const ctx = canvas.getContext('2d');      fileInput.addEventListener('change', function() {       const file = fileInput.files[0];       const reader = new FileReader();        reader.onload = function(event) {         const img = new Image();         img.onload = function() {           // Set canvas dimensions to desired crop size           const cropWidth = 100; // Desired width of cropped image           const cropHeight = 100; // Desired height of cropped image           canvas.width = cropWidth;           canvas.height = cropHeight;            // Calculate crop position (example: top-left corner)           const cropX = 50; // Starting x-coordinate           const cropY = 50; // Starting y-coordinate            // Draw the cropped portion of the image on the canvas           ctx.drawImage(img, cropX, cropY, cropWidth, cropHeight, 0, 0, cropWidth, cropHeight);         };         img.src = event.target.result;       };        if (file) {         reader.readAsDataURL(file);       }     });   </script> </body> </html>

Output:

Screenshot-2024-11-08-125848 — Choose Image

Screenshot-2024-09-13-163908 — Original Image

Screenshot-2024-11-08-130006 — Cropped Image

Explanation:

File Input: The <input type="file"> element allows users to select an image from their device.
Reading the Image: A FileReader object reads the selected image file and converts it to a data URL, which can be used as the src of an Image object.
Loading the Image: Once the image is loaded, the canvas dimensions are set to the desired crop size.
Cropping: The drawImage() method of the canvas context (ctx) is used to crop and draw the specified portion of the image. It takes several parameters:
- img: The image to draw.
- cropX and cropY: The starting coordinates of the crop area within the source image.
- cropWidth and cropHeight: The dimensions of the crop area.
- 0, 0, cropWidth, cropHeight: The coordinates and dimensions to draw the cropped portion on the canvas.

Key Points:

drawImage() Method: This method is key to cropping. The first four parameters specify the source image and crop area, while the last four parameters specify the destination coordinates and size on the canvas.
Canvas Resizing: Setting the canvas dimensions controls the size of the cropped output.
Flexible Cropping: You can adjust cropX, cropY, cropWidth, and cropHeight to crop different areas of the image.

This approach provides a simple way to crop images in the browser using only JavaScript and <canvas>. It's efficient for image manipulation tasks and does not require any server-side processing