出现这个问题主要是php gd扩展的问题
1.更新软件源
apt-get update
2.安装相关库
apt-get install -y libwebp-dev libjpeg-dev libpng-dev libfreetype6-dev zlib1g-dev
3.解压源码
docker-php-source extract
4.编译
cd /usr/src/php/ext/gd
docker-php-ext-configure gd --with-webp=/usr/include/webp --with-jpeg=/usr/include --with-freetype=/usr/include/freetype2
5.安装
make && make install
6.安装扩展
docker-php-ext-install gd