I have a front-end program for PND's running Windows CE (both 5.0 and 6.0) It user a high quantity of images (currently in png format) as buttons or for decoration purposes. The images are loaded from the SD Card via the new Bitmap(path);
I'm currently using v3.5 of the framework.
Upon loading, OS + my application have consumed 75 to 80% of the device's memory.
Wich good ways are there to optimize all that files?
The only ways that come to my mind to optimise these picture would be to resize them to the real size they are needed (like most icons will be used in a 16x16 size) and if you store also as bitmap no your card you can also set the used color palette to a size that matches the exact needs of the given picture (e.g. a picture of 16x16 has 256 pixels. So you need a maximum palette of 256 colors, but maybe also a self-defined 16 color palette is enough, cause in your picture are only 16 different colors.)
As a second approach you could also check if you maybe have the same picture multiple times loaded. In this case you should load it only once and use it multiple times.
A last one, that came to my mind belongs to background pictures. If you have a solid background you don't need a fully sized image of it. Just take a 1x1 bitmap and stretch it to the needed size. The same counts for gradient backgrounds, but in this case you have a 1x2 bitmap which will be stretched. And last but not least if you have a regular pattern, just take the smallest unique brick out of it and use some tile mechanism.
If you create the OS, is it possible to store the images as part of the OS?
In case it is possible, and the image is loaded fully to RAM, you can load the images only on a need to display basis and unload them when not needed. This will eliminate some loading time as well since accessing RAM is faster than accessing the SD card.
Another trick in with the same concept would be to copy all the images to a RAM based FS and load them only on a need basis - the down side is that this needs to be done after every reboot.