How to reduce png Picture without losing transparent Color by php

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There are two main ways to use the gd library:

The copy code is as follows:

Imagecolorallocatealpha / / assign colors + alpha

Imagesavealpha / / set to save complete alpha channel information when saving png images

Code example:

The copy code is as follows:

/ / get the source image gd image identifier

$srcImg = imagecreatefrompng ('. / src.png')

$srcWidth = imagesx ($srcImg)

$srcHeight = imagesy ($srcImg)

/ / create a new diagram

$newWidth = round ($srcWidth / 2)

$newHeight = round ($srcHeight / 2)

$newImg = imagecreatetruecolor ($newWidth, $newHeight)

/ / assign color + alpha to fill the new image with color

$alpha = imagecolorallocatealpha ($newImg, 0,0,0127)

Imagefill ($newImg, 0,0, $alpha)

/ / copy the source image to the new image, and set to save the complete alpha channel information when saving the PNG image.

Imagecopyresampled ($newImg, $srcImg, 0,0,0,0, $newWidth, $newHeight, $srcWidth, $srcHeight)

Imagesavealpha ($newImg, true)

Imagepng ($newImg,'. / dst.png')

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