set opacity for canvas in copyResampled and add alpha example script

composer.json

@@ -1,6 +1,6 @@
 {
 	"name": "antonlukin/poster-editor",
-	"version": "5.14",
+	"version": "5.15",
 	"description": "Wrapper for PHP's GD Library for easy image manipulation",
 	"keywords": ["php", "image", "text", "gd"],
 	"homepage": "https://github.com/antonlukin/poster-editor",

example/alpha.php

@@ -0,0 +1,50 @@
+<?php
+/**
+ * Opacity image and text support example.
+ * php version 7.1
+ *
+ * @category PHP
+ * @package  PosterEditor
+ * @author   Anton Lukin <anton@lukin.me>
+ * @license  MIT License (http://www.opensource.org/licenses/mit-license.php)
+ * @link     https://github.com/antonlukin/poster-editor
+ */
+
+require_once __DIR__ . '/../vendor/autoload.php';
+
+try {
+    $image = new PosterEditor\PosterEditor();
+    $image->canvas(500, 500, array('color' => '#fff'));
+
+    $image->insert(
+        'images/icon.png',
+        array(
+            'y' => 50,
+            'opacity' => 0,
+        )
+    );
+
+    $image->insert(
+        file_get_contents('images/icon.png'),
+        array(
+            'y' => 200,
+            'opacity' => 40,
+        )
+    );
+
+    $icon = new PosterEditor\PosterEditor();
+    $icon->make(file_get_contents('images/icon.png'));
+
+    $image->insert(
+        $icon,
+        array(
+            'y' => 350,
+            'opacity' => 80,
+        )
+    );
+
+    $image->show('png');
+
+} catch(Exception $e) {
+    echo $e->getMessage();
+}

example/insert.php

@@ -16,13 +16,7 @@
     $image = new PosterEditor\PosterEditor();
     $image->make('images/bridge.jpg')->fit(1000, 600, 'bottom-left');
     $image->grayscale()->invert();
-
-    $image->insert(
-        'images/logo.png',
-        array(
-            'width' => 500,
-        )
-    );
+    $image->insert('images/logo.png');
 
     $image->show();
 

example/make.php

@@ -13,12 +13,13 @@
 require_once __DIR__ . '/../vendor/autoload.php';
 
 try {
-    $file = file_get_contents('images/bridge.jpg');
-
     $image = new PosterEditor\PosterEditor();
-    $image->make($file)->downsize(null, 200)->invert()->show();
+    $image->make(file_get_contents('images/bridge.jpg'))->downsize(null, 1000)->invert();
+
+    $logo = new PosterEditor\PosterEditor();
+    $logo->make('images/logo.png')->downsize(null, 100)->invert();
 
-    $image->insert('images/logo.png')->show('png');
+    $image->insert($logo, array('y' => 0))->show('png');
 
 } catch(Exception $e) {
     echo $e->getMessage();

example/opacity.php

@@ -21,7 +21,6 @@
         array(
             'x' => 600,
             'y' => 0,
-            'height' => 100,
             'opacity' => 0,
         )
     );
@@ -31,7 +30,6 @@
         array(
             'x' => 600,
             'y' => 120,
-            'height' => 100,
             'opacity' => 40,
         )
     );
@@ -41,7 +39,6 @@
         array(
             'x' => 600,
             'y' => 240,
-            'height' => 100,
             'opacity' => 80,
         )
     );
@@ -88,7 +85,7 @@
         )
     );
 
-    $image->show();
+    $image->show('png');
 
 } catch(Exception $e) {
     echo $e->getMessage();

src/PosterEditor.php

@@ -23,7 +23,7 @@
   * @package  PosterEditor
   * @author   Anton Lukin <anton@lukin.me>
   * @license  MIT License (http://www.opensource.org/licenses/mit-license.php)
-  * @version  Release: 5.14
+  * @version  Release: 5.15
   * @link     https://github.com/antonlukin/poster-editor
   */
 class PosterEditor
@@ -155,12 +155,12 @@ public function insert($data, $options = array(), &$boundary = array())
 
         list($width, $height, $type, $source) = $image;
 
-        // We need to reverse opacity format for imagecopymergeAlpha function.
+        // We need to reverse opacity format for copyMergeAlpha function.
         $opacity = 100 - $options['opacity'];
 
         $options = $this->calcPosition($options, $width, $height);
 
-        $this->imagecopymergeAlpha($this->resource, $source, $options['x'], $options['y'], 0, 0, $width, $height, $opacity);
+        $this->copyMergeAlpha($this->resource, $source, $options['x'], $options['y'], 0, 0, $width, $height, $opacity);
 
         imagedestroy($source);
 
@@ -1254,7 +1254,7 @@ protected function calcPosition($options, $width, $height)
      */
     protected function copyResampled($source, $dx, $dy, $sx, $sy, $dw, $dh, $sw, $sh)
     {
-        $this->canvas($dw, $dh);
+        $this->canvas($dw, $dh, array('opacity' => 100));
 
         imagecopyresampled($this->resource, $source, $dx, $dy, $sx, $sy, $dw, $dh, $sw, $sh);
         imagedestroy($source);
@@ -1277,7 +1277,7 @@ protected function copyResampled($source, $dx, $dy, $sx, $sy, $dw, $dh, $sw, $sh
      *
      * @return void
      */
-    public function imagecopymergeAlpha($resource, $source, $dx, $dy, $sx, $sy, $sw, $sh, $pct)
+    public function copyMergeAlpha($resource, $source, $dx, $dy, $sx, $sy, $sw, $sh, $pct)
     {
         $cut = imagecreatetruecolor($sw, $sh);