I'm having troubles when trying to create an image using imagecreatefromjpeg using this Dockerfile to generate the container:
FROM  php:7.1-apache
RUN apt-get update && \
    apt-get install -y -qq git \
        libjpeg62-turbo-dev \
        apt-transport-https \
        libfreetype6-dev \
        libmcrypt-dev \
        libpng12-dev \
        libssl-dev \
        zip unzip \
        nodejs \
        npm \
        wget \
        vim
RUN pecl install redis && docker-php-ext-enable redis
RUN docker-php-ext-install -j$(nproc) iconv mcrypt zip pdo pdo_mysql gd bcmath
COPY ./containers/yii.conf /etc/apache2/sites-available/000-default.conf
RUN for mod in rewrite headers; do a2enmod $mod; done && service apache2 restart
WORKDIR /var/www/html/
GD was correctly installed (libjpeg too - both appearing in php -i and phpinfo()) but imagecreatefromjpeg does not works and I don't know why.
I also ran apt install libjpeg-dev libpng-dev libfreetype6-dev trying to ~force~ reinstallation (or reconfiguration) but seems doesn't succeded (yes, I also restart the container).
root@e8db647c96c4:/var/www/html# php -i | grep -i GD
/usr/local/etc/php/conf.d/docker-php-ext-gd.ini,
gd
GD Support => enabled
GD Version => bundled (2.1.0 compatible)
gd.jpeg_ignore_warning => 1 => 1
root@e8db647c96c4:/var/www/html# 
root@e8db647c96c4:/var/www/html# docker-php-ext-enable gd
warning: gd (gd.so) is already loaded!
root@e8db647c96c4:/var/www/html# 
I've tried apt install libgd2-xpm-dev* and apparently it doesn't solves the problem.
Solved
I was missing to put
RUN docker-php-ext-configure gd --with-freetype-dir=/usr/include/ --with-jpeg-dir=/usr/include/
RUN docker-php-ext-install -j$(nproc) gd
into my Dockerfile.
Full revised Dockerfile:
FROM  php:7.1-apache
RUN apt-get update && \
    apt-get install -y -qq git \
        libjpeg62-turbo-dev \
        apt-transport-https \
        libfreetype6-dev \
        libmcrypt-dev \
        libpng12-dev \
        libssl-dev \
        zip unzip \
        nodejs \
        npm \
        wget \
        vim
RUN pecl install redis && docker-php-ext-enable redis
RUN docker-php-ext-configure gd --with-freetype-dir=/usr/include/ --with-jpeg-dir=/usr/include/
RUN docker-php-ext-install -j$(nproc) iconv mcrypt zip pdo pdo_mysql gd bcmath
COPY ./containers/yii.conf /etc/apache2/sites-available/000-default.conf
RUN for mod in rewrite headers; do a2enmod $mod; done && service apache2 restart
WORKDIR /var/www/html/
 
     
     
     
     
     
    