How to compress a jpg image in WinRT/XAML?

Question

I need to compress large jpegs for display in (Bing) map markers.

I thought a found a way to do it here, but both Bitmap and Size are unrecognized in my WinRT/XAML (Windows Store) app.

Can the code by sikender be tweaked, or is this a "whole 'nuther animal"?

Answer 1

That's a "whole 'nuther animal". The linked code relies on System.Drawing, one of the graphics packages for desktop apps. System.Drawing is not available to Windows Store apps.

Windows Store apps use the Windows.Graphics.Imaging namespace and the BitmapDecoder and BitmapEncoder classes (decoder to convert the original file to raw pixels and encoder to convert the raw pixels into the new format).

MSDN goes over the process in How to decode an image and How to edit an image and puts it all together in the Simple Imaging sample

The basic steps:

• Read the original file into a StorageFile
• Open the StorageFile and create a BitmapDecoder based on its stream
• Create a target stream to encode into
• Create a BitmapEncoder based on the BitmapDecoder
• Set up a BitmapTransform with the changes you want to make (scaling down)
• Flush the encoder into the target stream