While most image creation software such as Photoshop will have options for selecting a progressive compression algorithm when you manually export an image as a JPEG, Filestack allows the creation of progressive JPEGs to be done programmatically, enabling you to integrate them easily into your website or application. Creating to a progressive JPEG is merely a matter of specifying the output format as “pjpg” — so you will add output=f:pjpg as part of your URL to filestack API.
To turn an existing image into a progressive image you would take its original URL:
https://upload.wikimedia.org/wikipedia/en/9/95/Legendary_kiss_V%E2%80%93J_day_in_Times_Square_Alfred_Eisenstaedt.jpg
And turn it into the following:
http://process.filestackapi.com//output=f:pjpg/https://upload.wikimedia.org/wikipedia/en/9/95/Legendary_kiss_V%E2%80%93J_day_in_Times_Square_Alfred_Eisenstaedt.jpg
This syntax allows the creation of progressive JPEGs to be chained with any other operations you wish to do with the image. In the following example, the image is first resized and then converted it to a progressive JPEG:
http://process.filestackapi.com/resize=width:750/output=f:pjpg/https://upload.wikimedia.org/wikipedia/en/9/95/Legendary_kiss_V%E2%80%93J_day_in_Times_Square_Alfred_Eisenstaedt.jpg
Because the conversion between baseline and progressive JPEGs is lossless, there is some flexibility in how you order this operation with other transformations that you do. A detailed list of formats that you may convert to a JPEG can be found in the Filestack documentation on transformation.