Hacker News Reader

Comment by wizzwizz4 | Hacker News Reader

I don't see how using a BMP would've taken a hit on RAM; it needs to decompress the JPEG to display on the screen anyway, after all.

View on HN

Well, maybe you have to remember the capacities of these days. If my memory serves me right, a "good" computer for win98se was 64 MB of RAM. But of course, there were plenty of "less powerful" ones still running, with 32 or even 16 MB of RAM. With such limitation, I can see how a 800x600 BMP image can become a drain on RAM. The swap engine tries to make up for it transparently by using swap space on spin-disk HDD, but then, it becomes sloooow.

I think the parent is saying that the jpeg will need to be stored uncompressed in ram - likely in exactly the same format as the bmp is stored in memory - for the graphics system to actually render it out to screen. Not that any "extra" cost of a BMP would be trivial.

So, after they're loaded and (possibly) scaled to fit the screen, I'd expect every background image to use exactly the same memory amount.

> So, after they're loaded and (possibly) scaled to fit the screen, I'd expect every background image to use exactly the same memory amount.

Well, not centered or tiled backgrounds, which I recall Windows did support, and upscaling could be done on a per-pixel basis (although I don't know if that was supported), but yes, the image format shouldn't matter.

I don't know the implementation details - but I wouldn't be surprised if it kept a full-screen-size already-scaled/tiled/centered image somewhere in memory

Back when win95 and co were being made, decoding an image was a lot of work for the hardware, I suspect they'll try to make restoring the background (e.g. dragging a window around and changing what's occluded) to be the simplest bitblt they can.

Reply on news.ycombinator.com