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In modern websites and applications, vintage-style filter effects are often used to give images a unique atmosphere and emotional tone. PHP offers a rich set of image processing libraries, among which the imageconvolution function is a powerful tool that applies convolution filters to images, achieving various special effects. Today, we’ll share how to use the imageconvolution function to create a vintage filter effect.
A convolution filter is an image processing technique that applies a filter matrix (or convolution kernel) to each pixel of an image, altering the image’s color and brightness. The output value of each pixel depends on the weighted average of its surrounding pixels, with weights determined by the values in the filter matrix. By using different filter matrices, effects such as sharpening, blurring, and edge detection can be achieved. A vintage filter uses a specific matrix to give the image a nostalgic, warm style.
In PHP, imageconvolution is a function used to perform convolution operations. Its basic usage is as follows:
bool imageconvolution ( resource $image , array $matrix , float $divisor , int $offset )
$image: The image resource to be processed.
$matrix: The convolution kernel, a two-dimensional array defining the weight coefficients for each pixel.
$divisor: A value used to normalize the matrix, usually the sum of the matrix values.
$offset: An offset added to the convolution result to adjust brightness.
Load the Image
First, we need to load an image to apply the filter on. You can load images in different formats using functions like imagecreatefromjpeg() or imagecreatefrompng().
Define the Vintage Filter Matrix
The key to the vintage filter is using the right convolution kernel. Here’s a simple vintage-style filter matrix that slightly warms the image tone by enhancing yellow and red components:
$matrix = [
[0.1, 0.2, 0.1],
[0.2, 1.0, 0.2],
[0.1, 0.2, 0.1]
];
This matrix subtly enhances and adjusts the colors of the image, bringing a soft vintage effect.
Apply the Convolution Operation
Use the imageconvolution function to apply the above matrix to the image. To achieve the vintage effect, set appropriate divisor and offset values.
$image = imagecreatefromjpeg('your-image.jpg'); // Load the image
$divisor = 1; // No normalization
$offset = 0; </span>// No brightness offset
<p>imageconvolution($image, $matrix, $divisor, $offset); // Apply the convolution filter<br>
</span>Save or Output the Image
After processing, use functions like imagejpeg() or imagepng() to save the filtered image as a file, or output it directly to the browser:
header('Content-Type: image/jpeg');
imagejpeg($image); // Output the processed image
imagedestroy($image); // Destroy the image resource and free memory
Adjust Tone and Saturation
To make the vintage effect more prominent, besides convolution, you can also use other image processing techniques such as adjusting tone, saturation, or contrast. These adjustments help to emphasize the vintage style of the image.
Add Noise Effects
Vintage-style images often have some noise, which gives the image a more aged feel. This effect can be simulated using simple random noise functions.
Combine Filters with Blur Effects
Vintage filters can be combined with blur effects to further simulate the feel of old photos. For example, using the imagefilter() function with a Gaussian blur filter adds softness to the image.
imagefilter($image, IMG_FILTER_GAUSSIAN_BLUR); // Gaussian blur
Use Gradient Backgrounds
If your vintage filter is applied to an image with a background, try adding gradient backgrounds to further enhance the nostalgic atmosphere.
Vintage Color Matrices
You can also modify the weights of RGB components to shift colors, such as increasing red and green while reducing blue, to create vintage yellowish or reddish tones.
Using PHP’s imageconvolution function to create vintage filter effects offers a simple and effective way to alter the appearance of images. By adjusting convolution kernels and combining other image processing techniques, you can achieve richer vintage effects. Mastering these methods allows you to add more artistic image processing to your website or app, delivering a more nostalgic visual experience for users.
