Image enlargement factor

[kool]

Hi,
I want to learn about Image enlargement factor, I have seen replays around, but was hard for me know it, got complicated and I decided to make thread.

what means close to .5 downsize and close to 2x upscale?

For example when resolution for DVD is 720x480 what would be .5 downsize ? or any other number

* For 1920x1080 how would you calculate it ?

* What is the meaning of enlarge image by 2x 4x 7x or 8x

Thanks.

[Didée]

You need to know elementary math. Someone gives you three bags. In each bag there are five apples. How many apples do you have?

Say, the source is 640x480.

Upsize by x4: (640*4) x (480*4) => 2560x1920

Downsize 0.5: (640*0.5) x (480*0.5) => 320x240

[kool]

Someone gives you three bags. In each bag there are five apples. How many apples do you have?


:p 15

So here we calculated for upsize with "*" and Downsize "/" and will go like this

Upsize by x2 : (720*2) x (480*2) => 1440x960

Downsize by .5 (720/2) x (480/2) => 360x240

Downsize by .3 (720/3) x (480/3) => 240x160

[Gavino]

Downsize by .3 (720/3) x (480/3) => 240x160
No.
720 x 0.3 = 216, 480 x 0.3 = 144, so 216x144.
240x160 would be downsize by 0.33333...

[kool]

OK Gavino, now I got the idea how to calculate it. in 3th one I divided, that is why I got wrong number, So in both cases we use the (Multiple "*") to calculate the Upsize and downsize?

Thank you Didee and Gavino.