How to generate progressive JPG with ImageResizer.net

Question

I am using the following code to generate a progressive JPG:

ImageResizer.ImageBuilder.Current.Build(srcFileName, dstFileName, new ResizeSettings("progressive=true"));

I am verifying if the JPG is progressive using ImageMagik identify command:

identify -verbose dstfile.jpg

And I get:

Interlace: None

I am generating progressive JPG files using Photoshop and identify does report:

Interlace: JPEG

Looking at documentation, this feature was added on version 3.1 Dec 7 2011. I am using version 3.3.2.447. I am not sure if I am missing a plug-in or additional commands.

Answer 1

Progressive jpeg encoding is only available with the FreeImageEncoder plugin installed - you must also use the &encoder=freeimage command. Neither WIC nor GDI+ offer progressive jpeg encoding, but both WIC and FreeImage support subsampling control.

Also note that progressive jpegs require more mobile device RAM to decompress, and only offer a speed benefit at larger output sizes (I.e, > 600x600)