PHP下使用強大的imagick輕松生成組合縮略圖，imagick縮略圖

<code class="meta">project: blog
target: use-imagick-to-composite-images-thumbnail.md
date: 2016-02-19
status: publish
tags:
    - php
    - imagick
    - thumbnail
categories:
    - php
</code>

這里說的imagick 是 ImageMagick 在PHP下的擴展。使用pecl安裝起來那叫一個輕松簡單 —— 一條命令就搞定：

<code class="sh">sudo pecl install imagick
</code>

（擴展裝好后還是要在php.ini中加上extension=imagick.so，然后記得重啟apache或php-fpm服務。）

最近有個需求是要把多張圖片組合起來生成縮略圖，剛好用用這個強大的imagick擴展。
這個需求是要這樣生成縮略圖：

這規(guī)則還真不少，不過還不算太過復雜，很快搞出來了：

<code class="php">namespace \clarence\thumbnail;
class Thumbnail extends \Imagick
{
    /**
     * @param array $images
     * @param int $width
     * @param int $height
     * @return static
     * @throws ThumbnailException
     */
    public static function createFromImages($images, $width, $height){
        if (empty($images)){
            throw new ThumbnailException("No images!");
        }

        $thumbnail = new static();
        $thumbnail->newImage($width, $height, &#39;white&#39;, &#39;jpg&#39;);
        $thumbnail->compositeImages($images);

        return $thumbnail;
    }

    public function compositeImages($images){
        $imagesKeys = array_keys($images);
        $compositeConfig = $this->calcCompositeImagesPosAndSize($images);

        foreach ($compositeConfig as $index => $cfg){
            $imgKey = $imagesKeys[$index];
            $img = new \Imagick($images[$imgKey]);
            $img = $this->makeCompositeThumbnail($img, $cfg);
            $this->compositeImage($img, self::COMPOSITE_OVER, $cfg[&#39;to&#39;][&#39;x&#39;], $cfg[&#39;to&#39;][&#39;y&#39;]);
        }
    }

    protected function makeCompositeThumbnail(\Imagick $img, $cfg){
        $img->cropThumbnailImage($cfg[&#39;size&#39;][&#39;width&#39;], $cfg[&#39;size&#39;][&#39;height&#39;]);
        return $img;
    }

    protected function calcCompositeImagesPosAndSize($images){
        $width = $this->getImageWidth();
        $height = $this->getImageHeight();

        switch(count($images)){
            case 0:
                throw new ThumbnailException("No images!");
            case 1:
                // | 0 |
                return [
                    0 => [
                        &#39;to&#39; => [ &#39;x&#39; => 0, &#39;y&#39; => 0 ],
                        &#39;size&#39; => [
                            &#39;width&#39; => $width,
                            &#39;height&#39; => $height,
                        ]
                    ]
                ];
            case 2:
                // | 0 | 1 |
                return [
                    0 => [
                        &#39;to&#39; => [ &#39;x&#39; => 0, &#39;y&#39; => 0 ],
                        &#39;size&#39; => [
                            &#39;width&#39; => $width / 2,
                            &#39;height&#39; => $height,
                        ]
                    ],
                    1 => [
                        &#39;to&#39; => [ &#39;x&#39; => $width / 2, &#39;y&#39; => 0],
                        &#39;size&#39; => [
                            &#39;width&#39; => $width / 2,
                            &#39;height&#39; => $height,
                        ]
                    ]
                ];
            case 3:
                // | 0 | 1 |
                // | 2 |   |
                return [
                    0 => [
                        &#39;to&#39; => [ &#39;x&#39; => 0, &#39;y&#39; => 0 ],
                        &#39;size&#39; => [
                            &#39;width&#39; => $width / 2,
                            &#39;height&#39; => $height / 2,
                        ]
                    ],
                    1 => [
                        &#39;to&#39; => [ &#39;x&#39; => $width / 2, &#39;y&#39; => 0],
                        &#39;size&#39; => [
                            &#39;width&#39; => $width / 2,
                            &#39;height&#39; => $height,
                        ]
                    ],
                    2 => [
                        &#39;to&#39; => [ &#39;x&#39; => 0, &#39;y&#39; => $height / 2 ],
                        &#39;size&#39; => [
                            &#39;width&#39; => $width / 2,
                            &#39;height&#39; => $height / 2,
                        ]
                    ],
                ];
            default:
                // >= 4:
                // | 0 | 1 |
                // | 2 | 3 |
                return [
                    0 => [
                        &#39;to&#39; => [ &#39;x&#39; => 0, &#39;y&#39; => 0 ],
                        &#39;size&#39; => [
                            &#39;width&#39; => $width / 2,
                            &#39;height&#39; => $height / 2,
                        ]
                    ],
                    1 => [
                        &#39;to&#39; => [ &#39;x&#39; => $width / 2, &#39;y&#39; => 0],
                        &#39;size&#39; => [
                            &#39;width&#39; => $width / 2,
                            &#39;height&#39; => $height / 2,
                        ]
                    ],
                    2 => [
                        &#39;to&#39; => [ &#39;x&#39; => 0, &#39;y&#39; => $height / 2 ],
                        &#39;size&#39; => [
                            &#39;width&#39; => $width / 2,
                            &#39;height&#39; => $height / 2,
                        ]
                    ],
                    3 => [
                        &#39;to&#39; => [ &#39;x&#39; => $width / 2, &#39;y&#39; => $height / 2],
                        &#39;size&#39; => [
                            &#39;width&#39; => $width / 2,
                            &#39;height&#39; => $height / 2,
                        ]
                    ],
                ];
        }
    }
}

</code>

用個試試：

<code class="php">$thumbnail = \clarence\thumbnail\Thumbnail::createFromImages($srcImages, 240, 320);
$thumbnail->writeImage($outputDir."/example.jpg");

</code>

效果立馬出來了：

贊一個~

（詳細代碼見 http://github.com/clarence-pan/thumbnail)