how to dynamically scale a screen in coronasdk - lua

Question

my current config file is for ipad retina and it works perfectly, however when i select a device with a smaller screen the image becomes warped.
here is my current config.lua
application = {
content = {
width = 768,--aspectRatio > 1.5 and 800 or math.ceil( 1200 / aspectRatio ),
height = 1024,
scale = "none",
fps = 60,
imageSuffix = {
["#2x"] = 1.3,
}
}
}
i would like to know if there is a way to dynamically set the width or height without hardcoding these figures for each invdividual device.

Answer 1

I use letterbox scaling for that.
application =
{
content =
{
width = 320,
height = 480,
scale = "letterbox",
xAlign = "center",
yAlign = "center",
imageSuffix =
{
["#2"] = 1.8,
["#4"] = 3.6,
},
},
}
Then I can use display.newImageRect, provided with dimensions of image for 320,480 device resolutions. #2 and #4 image suffixes are images 2x and 4x bigger.
Here is excellent article to get you in the corona scaling features:
http://coronalabs.com/blog/2010/11/20/content-scaling-made-easy/

Answer 2

I suggest you read this article about "the ultimate config/modernizing the config".
Some screens are wider while others are more narrow. If we take
resolution out of the equation, its easier to visualize the screens.
Corona makes it easy to take resolution out of the picture using
Dynamic Scaling. With Dynamic Scaling, you can use a common set of
screen coordinates and Corona will automatically scale the text and
graphics for different resolution screens. It can scale upwards or
downwards depending on your starting point. It also can substitute
higher resolution images when it needs to scale up. This is all
managed by a Lua file in your project folder called config.lua.
Since available resolutions vary considerably, it’s helpful to use the
same scale for each device. It doesn’t matter if you’re on an iPhone
3GS at 320×480 or a Retina iPad at 1536×2048, the location (0,0)
represents the top-left corner and (320,480), in vertical portrait
mode, is the bottom-right corner. The screen center is (160,240).
Each point, in this case, is one pixel on a lower-resolution device
like the 3GS, which has a native screen resolution of 320×480, while
each point is four pixels on a Retina iPad. Don’t worry about the math
— Corona will handle it for you.
Source: http://coronalabs.com/blog/2012/12/04/the-ultimate-config-lua-file/
local aspectRatio = display.pixelHeight / display.pixelWidth
application = {
content = {
width = aspectRatio > 1.5 and 320 or math.ceil( 480 / aspectRatio ),
height = aspectRatio < 1.5 and 480 or math.ceil( 320 * aspectRatio ),
scale = "letterBox",
fps = 30,
imageSuffix = {
["#2x"] = 1.3,
},
},
}