How to solve the problem of php image compression failure

PHP is a popular Web programming language that also occupies an important position in the field of image processing. Although PHP comes with many image processing functions, in my recent project, I encountered a frustrating problem - image compression failed.

In this project, I need to compress user-uploaded images to a specified size and quality for display in a web application. To achieve this I used the image processing functions from the PHP GD library. However, even though I followed all the recommended best practices like setting memory limits, checking image formats, and using the latest library versions, I still couldn't successfully compress the images.

First, I tried to use the imagejpeg function in the code to compress the JPEG image. Here's the code I tried:

<?php
// Load the image
$image = imagecreatefromjpeg(&#39;image.jpg&#39;);

// Resize the image
$resizedImage = imagescale($image, 200);

// Compress and save the image
imagejpeg($resizedImage, &#39;compressed.jpg&#39;, 80);
?>

Although I tried various different compression qualities, the resulting image always ended up being larger than the original image, not smaller. I've tried different JPEG library versions but still to no avail.

Next, I started experimenting with other image formats like PNG and WebP. I used the following code to compress a PNG image:

<?php
// Load the image
$image = imagecreatefrompng(&#39;image.png&#39;);

// Resize the image
$resizedImage = imagescale($image, 200);

// Compress and save the image
imagepng($resizedImage, &#39;compressed.png&#39;, 9);
?>

However, I ran into the same problem again - the resulting image was larger than the original image.

Finally, I tried Google's WebP format in hopes of reducing the image size. I'm using the libwebp library and the following code to compress the image:

<?php
// Load the image
$image = imagecreatefromjpeg(&#39;image.jpg&#39;);

// Resize the image
$resizedImage = imagescale($image, 200);

// Convert the image to WebP format
imagewebp($resizedImage, &#39;compressed.webp&#39;, 80);
?>

Unfortunately, I can't successfully compress the image, even using the WebP format.

After many attempts, I finally found the solution. The problem was that I was using imagescale in my code. This function actually generates a new copy of the image, rather than actually compressing the original image. Therefore, using this function results in the resulting image being larger than the original image.

To solve this problem, I instead used the imagecopyresampled function, which compresses the original image without making a new copy of the image. Here is the code I modified successfully:

<?php
// Load the image
$image = imagecreatefromjpeg(&#39;image.jpg&#39;);

// Get the original dimensions of the image
$width = imagesx($image);
$height = imagesy($image);

// Calculate the new dimensions of the image
$newWidth = 200;
$newHeight = $height * ($newWidth / $width);

// Create a new image with the new dimensions
$resizedImage = imagecreatetruecolor($newWidth, $newHeight);

// Copy and resample the original image into the new image
imagecopyresampled($resizedImage, $image, 0, 0, 0, 0, $newWidth, $newHeight, $width, $height);

// Compress and save the image
imagejpeg($resizedImage, &#39;compressed.jpg&#39;, 80);
?>

Now, by using the imagecopyresampled function, I can easily compress JPEG, PNG, and WebP images without compression failure. I hope my experience can help other web developers avoid running into the same problems with image processing.

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