How to merge multiple transparent pngs with different size into one image without cropping, using PHP GD library?

Question

I would like to merge multiple pngs with transparent background into one image. Images have different sizes and because of this, when images are placed over the top of each other, only within the size of the uppermost image are shown the parts of the merged images.

It's like the last image applies like a mask for the images merged before. I would like to see all the images merged with their original size, without cropping the parts hanging over the size of the last image.

Here is the code I'm using currently:

$images = array();
    foreach (scandir($this->img_dir) as $key => $dirname) {
        if(!strstr($dirname, "."))
        {
            if(isset($_GET[$dirname])) 
            {
                foreach ($this->layer_order as $lkey => $order) {
                    if($lkey == $dirname)
                        $images[$order] = glob($this->img_dir . "/" . $dirname . "/" . $_GET[$dirname] . ".png");
                }
            }
        }
    }


    $destination = imagecreatetruecolor(458, 600);


    imagealphablending($destination, true);
    imagesavealpha($destination, true);

    ksort($images);
    foreach($images as $key => $value) {        
        foreach ($value as $fn) {
            // Load image
            $source = imagecreatefrompng($fn);
            //$source = $this->resize_image($source, 50, 50, 2);

            // Copy over image
            imagecopy($destination, $source, 10, 50, 0, 0, 458, 600);

            // Free memory
            imagedestroy($source);
        }
    }

    return $destination;

Answer 1

I don't know if this is the best solution for what I tried to achive, but after several attempts and some research I used a fairly simple method to avoid the last image in the merging queue, mask the other images with it's relatively small size. This way every image will be merged and positioned accordingly the user wants, inside the specified canvas size, with their transparency.

I post the whole content of the function in case if someone needs a similar solution. This is a function inside a class.

    $images = array();

    // Foreach loop to set images order and creating an array with image paths using params from $_GET before merging
    foreach (scandir($this->img_dir) as $key => $dirname) {
        if(!strstr($dirname, "."))
        {
            if(isset($_GET[$dirname])) 
            {
                foreach ($this->layer_order as $lkey => $order) {
                    if($lkey == $dirname) {
                        $imageArray = glob($this->img_dir . "/" . $dirname . "/" . ($dirname == "door" && isset($_GET['type']) ? $_GET['type']."/" : "") . $_GET[$dirname] . ".png");
                        foreach ($imageArray as $imgPath) {
                            $images[$order] = $imgPath;
                        }
                    }       
                }
            }
        }
    }

    // Allocate new image
    $destination = imagecreatetruecolor($this->canvas_width, $this->canvas_height);

    imagealphablending($destination, false);
    $col = imagecolorallocatealpha($destination, 255, 255, 255, 127);
    imagefilledrectangle($destination, 0, 0, $this->canvas_width, $this->canvas_height, $col);
    imagealphablending($destination, true);

    // Sort order
    ksort($images);

    // Merging images
    foreach($images as $key => $fn) {

        // Load image
        if(strstr($fn, "handle")) 
        {
            $source = $this->resizePng($fn, 0.18, 100, 205);
            imagecopy($destination, $source, 0, 0, 0, 0, $this->canvas_width, $this->canvas_height);
        }
        elseif (strstr($fn, "glass")) 
        {
            // Create a background image by filling a canvas with small image tiles. Params: $file, $shrink_ratio_percent, $column_size, $stretch
            $source = $this->multiplyMergeAndResizePngs($fn, 0.2095, 3, 3.6);
            // Applying mask on images based on black and white patterns
            if ($this->glass_mask)
                $source = $this->createMask($source, $this->glass_mask);
            imagecopy($destination, $source, 118, 28, 0, 0, $this->canvas_width, $this->canvas_height);
        }
        elseif (strstr($fn, "door")) 
        {    
            $source = imagecreatefrompng($fn);
            imagecopy($destination, $source, 32, 0, 0, 0, $this->canvas_width, $this->canvas_height);
        } else {
            $source = imagecreatefrompng($fn);
            imagecopy($destination, $source, 0, 0, 0, 0, $this->canvas_width, $this->canvas_height);
        }

        imagealphablending($destination, true);

        // Free memory
        imagedestroy($source);
    }

    return $destination;