Simulate imageflip() function without GD extension enabled

In PHP, imageflip() is a convenient function for image flipping, but only if you have to enable GD extension. For some servers that are restricted in environments or do not enable GD extensions for security and performance reasons, we can still simulate this feature in other ways. This article will introduce how to use pure PHP to implement imageflip() -like image flip function without relying on GD extensions.

1. Prerequisites and ideas

We take common image formats such as PNG or JPEG as an example, and the goal is to simulate the vertical flip (up and down) or horizontal flip (right and left and right) functions of the image. Since the GD function cannot be used, you can only operate on the image data directly. A feasible method is to convert the image into an array of pixels for processing. The following methods are recommended:

1. Use imagecreatefromstring() (requires GD)

2. Use Imagick extension (alternative, but still extension)

3. Pure PHP parses image data (low performance, but no extension at all)

This article will show a way to use the base64 data URI to load images into HTML5 Canvas, and then simulate similar processing through PHP.

2. Implement image flip through the browser and server

Although the PHP side cannot directly manipulate pixel data, we can upload the image, use HTML and JavaScript to flip it on the client, and then upload the processed image.

Sample HTML (used with the backend)