PHP GD Library Image Stitching Tutorial

Introduction

Image stitching is a common image processing technique where multiple small images are combined into a larger image to achieve various functions, such as creating puzzle games or generating photo walls. This article introduces how to use PHP and the GD library to implement image stitching, helping readers master basic image processing skills.

Overview of GD Library

The GD library is an open-source image processing library that provides functions for creating, manipulating, and outputting images. With PHP's GD library extension, dynamic image creation on web servers becomes easy. GD library can be used to perform tasks like scaling, rotating, cropping images, and adding text.

Step 1: Prepare Image Assets

First, gather the images you want to stitch together. The images can vary in size—GD library can automatically adapt to different image dimensions and perform the stitching seamlessly.

Step 2: Create a Canvas

In PHP, the first step is to create a canvas to hold the final stitched image. Using the imagecreatetruecolor() function from the GD library, you can create a canvas with specified dimensions.

$canvasWidth = 800; // Canvas width
$canvasHeight = 600; // Canvas height
$canvas = imagecreatetruecolor($canvasWidth, $canvasHeight);

Step 3: Load Images and Stitch Them Together

Using imagecreatefromjpeg() or imagecreatefrompng() functions, you can load the images to be stitched. Then, using the imagecopy() function, you can copy these smaller images onto the canvas.

$smallImage1 = imagecreatefromjpeg('small1.jpg');
$smallImage2 = imagecreatefromjpeg('small2.jpg');
// Stitch images
imagecopy($canvas, $smallImage1, 0, 0, 0, 0, imagesx($smallImage1), imagesy($smallImage1));
imagecopy($canvas, $smallImage2, 100, 0, 0, 0, imagesx($smallImage2), imagesy($smallImage2));

Step 4: Output the Stitched Image

You can use the imagejpeg() function to output the stitched image to the browser or save it to the file system.

header('Content-Type: image/jpeg');
imagejpeg($canvas, null, 100); // Output to browser
imagejpeg($canvas, 'output.jpg', 100); // Save to file

Step 5: Free Resources

To avoid memory leaks, it is important to destroy the image resources once the script has finished executing.

imagedestroy($canvas);
imagedestroy($smallImage1);
imagedestroy($smallImage2);

Conclusion

By using PHP and the GD library, we can easily implement image stitching functionality. This article covered the basic steps, and developers can modify and extend the functionality as needed. We hope this article helps you with image processing, and feel free to explore more image processing techniques.