h5-api/app/Handlers/CompressImageHandler.php

<?php

namespace App\Handlers;

class CompressImageHandler
{
    private $image;         //重绘图片
    private $imageinfo;     //重绘图片的具体信息(array)
    private $percent = 0.5;   //压缩比例，1为原像素比例

    //接收的图片文件
    public function Upload()
    {
        $file = $_FILES['img'];
        // 要上传图片的本地路径
        $filePath = $file['tmp_name'];
        // 对图片压缩重绘
        $this->_openImage($filePath);
        // 将重绘后的图片流赋值使用
        ob_start(); // 开始输出缓存.

        $fileName = $file['name'];
        $ext = pathinfo($fileName, PATHINFO_EXTENSION); // 后缀
        if ($ext == 'jpg' || $ext == 'jpeg') {
            imagejpeg($this->image); // imagejpeg()通常会输出图像, 由于ob_start(), 所以不会.
        }
        if ($ext == 'png') {
            imagepng($this->image); // imagepng()通常会输出图像, 由于ob_start(), 所以不会.
        }

        $contents = ob_get_contents(); // 把上面的输出保存为 $content
        ob_end_clean(); // 结束输出缓存.
        imagedestroy($this->image);

        return $contents;
    }

    /**
     * 内部：打开图片
     */
    private function _openImage($src)
    {
        list($width, $height, $type, $attr) = getimagesize($src);
        $this->imageinfo = array(
            'width' => $width,
            'height' => $height,
            'type' => image_type_to_extension($type, false),
            'attr' => $attr
        );
        $fun = "imagecreatefrom" . $this->imageinfo['type'];
        $this->image = $fun($src);
        $this->_thumpImage();
    }

    /**
     * 内部：操作图片
     */
    private function _thumpImage()
    {
        $new_width = $this->imageinfo['width'] * $this->percent;
        $new_height = $this->imageinfo['height'] * $this->percent;
        $image_thump = imagecreatetruecolor($new_width, $new_height);

        //绘制图片透明底色
        imagesavealpha($image_thump, true);
        $black = imagecolorallocate($image_thump, 0, 0, 0);
        imagefilledrectangle($image_thump, 0, 0, 150, 25, $black);
        $trans_colour = imagecolorallocatealpha($image_thump, 0, 0, 0, 127);
        imagefill($image_thump, 0, 0, $trans_colour);

        //将原图复制带图片载体上面，并且按照一定比例压缩,极大的保持了清晰度
        imagecopyresampled($image_thump, $this->image, 0, 0, 0, 0, $new_width, $new_height, $this->imageinfo['width'], $this->imageinfo['height']);
        imagedestroy($this->image);
        $this->image = $image_thump;
    }
}