Description
Currently, image representations are tied to zoom values (usually according device/monitor zooms). In some situation, one wants to draw images at sizes independent from any device/monitor zoom but may want to use an arbitrary zoom value or even an arbitrary size.
There are already GC#drawImage() methods accepting destination sizes and then performing according (potentially blurry) scaling of the images at the GC level.

Potential use cases:

• Images in (GEF) diagrams at arbitrary zoom values.
• Images filling some resizable area
• Custom UI zooms (in particular for the annotation ruler in editors): Ruler icons should scale with font size eclipse-platform/eclipse.platform.ui#3044

Goal
It shall be possible to draw images at a custom zoom/size at the best achievable quality. This means either

• rescaling from the most fitting zoomed version of the image that exists
• rasterizing the image at the according size from an SVG source

The first use cases I would expect to be supported are:

• Drawing in best possible quality in the GC#drawImage() methods accepting a destination size
• Scaling the annotation ruler according to a custom editor zoom with sharp images

Additional Knowledge
This will probably require new API to Image in SWT that allow to request an image at a specific size rather than a given zoom.

We potentially need to careful to not create additional handles/representations for each such size, as otherwise we can easily run out of handles (on Windows). Instead of providing the image data or a handle itself via Image API, we might also just provide API to perform an operation on some ImageData or handle for a specific image zoom/size, such that, e.g., the GC can pass a callback for performing the drawing operation on the Image and the Image itself takes care of providing according image data or a (temporary) handle.

This will also require extensions to the ImageLoader and FileFormat implementation, as for SVGs it will probably be necessary to allow passing sizes instead of zoom to the loading implementation.