thanks. Interesting! Don’t you experience memory problems on devices with low resolutions (which usually also have less available memory) with your approach?
thanks
Marco
I use 2048x1536 or 1536x2048 as my base and then just detect the offset (if one exists) with screenOriginX/screenOriginY.
I haven’t hit any memory issues but keep my graphics pretty optimized.
Thanks a lot! Could you give me a small example how you detect the offset?
thanks
Marco
A 2048x1536 image is in effect a 2048x2048 texture in memory. With 4 color channels, that means that that image is taking up 16MB of memory. iPhone 4’s and iPad 2’s only have 512M of memory and the OS takes up a lot of that. It doesn’t take too many of these files to eat up memory. Also when you’re on older hardware its more computationally harsh to downsize these images.
You can always move things fractional amounts with Corona. Moving something for .x to .x + 0.25 will move it one pixel on 4x devices.
Moving things fractional amounts wasn’t the issue. The problem was detecting fractional amounts of movement in the touch event.
In your touch function if you print out your event.x and event.y values you will see they are never fractional, they are always integers between 0-320 (if content width is set to 320). This means that you have to move your finger multiple ‘screen pixels’ on a hi res device before it detects that you’ve moved 1 ‘content pixel’. As I say it may be fine for most games, but you do lose some of the precision that you get by setting the content width/height to a higher value.
I agree with Alan here in that touch-coordinates cannot be fractional.
I’ve made a compromise and used 1026 x 684 to reduce memory requirements. Basically “iPad 1 resolution adjusted for a 4:3 aspect ratio”
I always design for exactly 2048x1536. This is the resolution of the retina iPads so I know things will look nice on even the top-end of devices. I only use one set of graphics - the highres one - and make sure all important content fits on the iPad screen ratio. iPhone 5 etc… just get to see more of the screen, but it is non-essential info. And then I just design smartly, to be honest, e.g. for full screen graphics, I would use a 1024 x 1024 blurry background scaled across the screen, with a smaller sharp and high-res image in front on part of the screen.
Of course your projects need to allow for this kind of setup.
@Rob, When i said 2048x1536 I wasn’t meaning to make your graphics 2048x2048 that would be silly 
I for one always use 2048x1536 as base “resolution” for anything from objective-c, java, openGL, directX, corona etc and so forth as it makes my life “a lot” easier to be able to support multiple devices,resolutions without swapping graphics or upsizing them or increaseing your package size with all your x2,x3,x4 etc images.
That being said @Rob is correct about the memory footprint which is why you need to be smart about how you manage your assets most if not all of the applications and/or games I have made have never gone over 40mb in texture memory. I test on iphone 4 all the way up to iphone 6+ now, and on the android side i test all the way back to the original droid and nook, all the way up to samsungs latest and nexus7’s etc.
And sure if you make all your graphics 2048x2048 and don’t use spritesheets etc. you are going to find yourself in a hurt really fast so like anything get all the input you can and then just make the best choice based on your situtation.
Just my two cents.
Interesting. That means you use one spritesheet (where assets are in retina iPad resolution) for all devices?
I’ve been assuming that using such a hi-res spritesheet/imagesheet on, let’s say an iPhone 4, would have a significant impact on performance and texture memory, so I’ve been creating my 1x, 2x, 4x sheets.
Disclaimer: What I do is not the views of Corona and/or any other developer just my own personal experience and you should get all input before making any changes to your app/game
I only design 1 size and use zoomEven in my config file and detect offset etc.
Using 1x, 2x, 4x is great when you want he best performance you can get but it has been my experience that if done right you don’t even need the headache. I have done this in the past only to find some devices having issues or not looking right or stretching etc. I really don’t like my images stretched, I am ok with them being shrunk down but hate them scaling up, I also am not a big fan of big downloads which can happen when you have a ton of assets and use 1x,2x,4x images and I have played with all resolutions.
I actually make my photoshop files at 2048x1536 “HOWEVER” what I don’t do is make any sprite sheet > 1024, and using some smart logic I can swap them in and out when i need them keeping my video memory footprint very low.
This does take some knowledge ahead of time knowing when and where to load imagesheets and the best place to add an image to a imagesheet for example putting a menu button inside of a game imagesheet isn’t the best way to go unless that image button is used a lot during game play. etc. and so forth.
But this is all just my own personal opinion and the best way for my apps/games
Asking what is the best resolution is like asking someone what is better php/.net or c# vs vb.net, mysql vs mssql etc. you are always going to get a different answer depending on who you ask
Thanks Christopher.
An interesting approach that I might just try myself 
If you make your background image 1536x2048, the texture size is 2048x2048x4.
Rob
I don’t use background images I build them on the fly with a imagesheet
But yes you are right about that