C++ GUI Development - Bitmap vs. Vector Graphics CPU Usage

Question

I'm currently in the process of designing and developing GUI's for some audio applications made in C++ (using the Juce framework).

So far I've been playing with using bitmap graphics to create custom sliders and dials, by using 'film strip' style images to animate the components (meaning when the user interacts with a slider it triggers a method that changes the offset of a film-strip image to change the components appearance). Depending on the size of the original image and the number of 'frames', the CPU usage level changes quite dramatically.

Firstly, what would be the most efficient bitmap file format to use in terms of CPU consumption? At the moment I'm using PNG images.

Secondly, would it be more efficient to use vector graphics for these kind of graphical components? I understand the main differences between bitmap and vector graphics, but I haven't found any information regarding their CPU usage levels with regard to GUI interaction.

Or would CPU usage be down to the particular methods/functions/libraries/frameworks being used?

Thanks!

Answer 1

Or would CPU consumption be down to the particular methods/functions/libraries/frameworks being used?

Any of these things could influence it.

Pixel based images might take a while to read off of disk the bigger they are. Compressed types might take more time to uncompress. Vector might take more time to render when are loaded.

That being said, I would definitely not expect that your choice of image type to have any impact on its performance. Since you didn't provide a code example it is hard to speculate beyond that.

In general, you would expect that the run-time costs of the images to happen when they are loaded. So whenever you create an image object. If you create an images all over the place, then maybe its expensive. It is possible that your film strip is recreating the images instead of loading them once and caching them.