I'm writing a mobile content adaptation plugin for a bespoke CMS in PHP. The CMS contains links to images with absolute URLs which are all 400 pixels wide and vary in height. I'd like to parse the HTML (which is stored in MySQL) and re-scale each image to a new width - this will vary according to the device. I'd also like to cache the images to prevent needlessly resizing them on-the-fly every time the page is loaded
What's the best way for me to achieve this in PHP using either ImageMagick or GD, please?