CODEWITHSUNDEEP
phptransparent
Temüjin
Temüjin

Reputation: 15548

imagecopyresampled with opacity

I want to add a small image on anther big image as a watermark with opacity.

I'm using imagecopyresampled to put image on anther image.

But, how to provide opacity for watermark image.

Please help me.

I'm using this simple example code for add watermark on image without opacity:

<?php

$background = imagecreatefrompng("background.png");

if ($background !== false) {
    $watermark = imagecreatefrompng("watermark.png");
    // Add watermark on background
    imagecopyresampled($background,$watermark,
        100, 100, 0, 0,
        128, 128, 128, 128);
    // Add image header
    header("Content-type: image/png");
    imagepng($background);
    imagedestroy($background);
}

For example:

This is background or main image

This is background or main image

This is watermark image

enter image description here

I want this type of output

enter image description here

Is it possible or not in PHP?

Upvotes: 3

Views: 1785

Answers (2)

Farshad
Farshad

Reputation: 1485

Try to use this opensource PHP project:

Image workshop https://github.com/Sybio/ImageWorkshop

Upvotes: 2

user4042110
user4042110

Reputation:

Just use this simple PHP function:

<?php

function filter_opacity(&$img, $opacity) //params: image resource id, opacity in percentage (eg. 80)
{
    if (!isset($opacity)) {
        return false;
    }
    $opacity /= 100;

    //get image width and height
    $w = imagesx($img);
    $h = imagesy($img);

    //turn alpha blending off
    imagealphablending($img, false);

    //find the most opaque pixel in the image (the one with the smallest alpha value)
    $minalpha = 127;
    for ($x = 0; $x < $w; $x++) {
        for ($y = 0; $y < $h; $y++) {
            $alpha = (imagecolorat($img, $x, $y) >> 24) & 0xFF;
            if ($alpha < $minalpha) {
                $minalpha = $alpha;
            }
        }
    }

    //loop through image pixels and modify alpha for each
    for ($x = 0; $x < $w; $x++) {
        for ($y = 0; $y < $h; $y++) {
            //get current alpha value (represents the TANSPARENCY!)
            $colorxy = imagecolorat($img, $x, $y);
            $alpha = ($colorxy >> 24) & 0xFF;
            //calculate new alpha
            if ($minalpha !== 127) {
                $alpha = 127 + 127 * $opacity * ($alpha - 127) / (127 - $minalpha);
            } else {
                $alpha += 127 * $opacity;
            }
            //get the color index with new alpha
            $alphacolorxy = imagecolorallocatealpha($img, ($colorxy >> 16) & 0xFF, ($colorxy >> 8) & 0xFF, $colorxy & 0xFF, $alpha);
            //set pixel with the new color + opacity
            if (!imagesetpixel($img, $x, $y, $alphacolorxy)) {
                return false;
            }
        }
    }

    return true;
}

Example of usage:

<?php
$image = imagecreatefrompng("img.png");
filter_opacity($image, 75);
header("content-type: image/png");
imagepng($image);
imagedestroy($image);

Source: http://php.net/manual/en/function.imagefilter.php

Upvotes: 3

Related Questions