Wrong aspect ratio for Circle[f]?

[asrael]

Hello.

Sorry, maybe a trivial question.

I'm drawing some Circles on a Lo and Hires screen.
On Lores it seems like it's almost a circle with correct aspect ratio.
But on Hires it seems to be more off.
So I suppose Circle doesn't calculate the right aspect ratio on its own depending on the screen.
Do I have to do it? How?


Cheers

[Daedalus]

Yes, that's correct. The Circle command assumes a 1:1 pixel aspect, so drawing a 20px radius circle will result in a circle 40px wide and 40px tall on the bitmap. A bitmap knows nothing about the aspect ratio of the current screenmode, since it's an independent object by itself so you have to calculate that yourself. If you haven't opened the screen yourself, you can query the size of it using ScreenWidth and ScreenHeight.

Handling it is relatively easy though: once you know the current screen dimensions you can check if it's roughly a 1:2 (hires) or a 1:1 (lores) screen. If it's a lores screen, just draw the circle with the desired radius:

Circle xpos, ypos, 20, #pen

If it's a hires screen, use the extra parameter to set separate radii for the X and Y axes, with the X radius twice the Y radius:

Circle xpos, ypos, 40, 20, #pen

[asrael]

OK, cool, thanks.

So is the radio something like: ScreenWidth / ScreenHeight * radius ?

[nocash]

No, not exactly.
The radio is for audio broadcasts.
The ratio is ScreenWidth / ScreenHeight, not including the radius.

[Daedalus]

I see what you're getting at, and the second radius will be something like that, yes. But I would suggest doing it differently because slight variations in screen size will cause slight variations in your circle. And with such low resolutions, often it looks better to have symmetry than perfect X:Y ratios. So I would check if the width of the screen was more than 2* the height, and then make the X radius 2* the Y radius. If the width of the screen is less than 2* the height I would make the X and Y radius the same.