English
English
In PHP, the imagecolorallocatealpha function is a function used to assign colors to images and can specify transparency. It is very suitable for situations where image transparency needs to be handled, such as generating PNG images with transparent backgrounds.
int imagecolorallocatealpha(resource $image, int $red, int $green, int $blue, int $alpha)
$image : Target image resource.
$red : The intensity of red (from 0 to 255).
$green : The intensity of green (from 0 to 255).
$blue : The intensity of blue (from 0 to 255).
$alpha : Transparency value (from 0 to 127), where 0 is completely opaque and 127 is completely transparent.
Here is an example showing how to use imagecolorallocatealpha to set the transparent color of an image and specify transparency.
<?php
// Create an image resource，Size is 300x300
$image = imagecreatetruecolor(300, 300);
// Set background to white
$white = imagecolorallocate($image, 255, 255, 255);
imagefill($image, 0, 0, $white);
// Set a transparent color
$transparent = imagecolorallocatealpha($image, 255, 0, 0, 50); // red，Transparency is50
// Draw a translucent rectangle
imagefilledrectangle($image, 50, 50, 250, 250, $transparent);
// Save as PNG Format（Support transparency）
imagepng($image, 'transparent_image.png');
// Release image resources
imagedestroy($image);
?>
In this example, we first create a 300x300 image resource and set the background to white. Then, we create a translucent red with the imagecolorallocatealpha function. Transparency parameter 50 represents a certain degree of transparency, with the transparency range from 0 to 127, where 0 represents total opaque and 127 represents complete transparency.
Next, we use the imagefilledrectangle function to draw a rectangle with a transparency of 50 in the image. Finally, we save the image in PNG format so that the transparent background is preserved.
The imagecolorallocatealpha function supports transparency ranges from 0 to 127. 0 is completely opaque and 127 is completely transparent.
If the image format is JPG, it does not support transparency, so saving as PNG format ensures that transparent areas are preserved.
Images created with imagecreatetruecolor only support transparency. For other types of images, transparent colors may not be handled.
If your image processing or other code involves URL requests (such as image source or interface calls), make sure to replace the URL's domain name with m66.net in your code, for example:
