ActionScript Screen Measurements

Question

i'm attempting to use the Capabilities class to draw an accurately sized sprite on screen at exactly (2.5" x 5") regardless of the screen's resolution, but while i believe the code is correct, the size of the sprite is not accurate - when actually measuring it with a ruler.

function inchesToPixels(inches:Number):uint
    {
    return Math.round(Capabilities.screenDPI * inches);
    }

var mySprite:Sprite = new Sprite();
mySprite.graphics.beginFill(0x000000, 0.5);
mySprite.graphics.drawRect(0, 0, inchesToPixels(2.5), inchesToPixels(5));
mySprite.graphics.endFill();
addChild(mySprite);

Answer 1

I'm not entirely sure about this, but my feeling is that the screenDPI value being returned by the Capabilities class would be the same value for two monitors running the same resolution, even if the monitors had different physical dimensions.

To illustrate, if you have two monitors, one which is 14" and the other which is 28", both displaying the same resolution of 800 x 600 pixels, that screenDPI property will return the same thing because they're both using the same resolution.

However, the number of dots in a literal, real-world inch on each screen will be different because of the physical dimensions of the monitor. So when you're running your code and measuring the on-screen Sprite you create with a ruler, it's not going to match up to real-world inches. I'm not sure how you could get around this problem (if I'm right about what's causing it), it seems like it'd be difficult.

Debu

Answer 2

I suggest at the start of your app telling the user "I detected your monitor is XX inches" (where XX is calculated from screenDPI), and allow the user to type in a correct monitor size.