pixels/inch and not pixels/cm?

guilleface

i just search the forum and find out that my images need to be 72 pixels/inch, but i think I'm being doing all my images at pixels/cm, so do i have to redo all my images again? is this why my circles look like oval on a device?

gyroscope

Hi @guilleface, more than likely! Yes, images have to be 72 ppi (pixels per inch).


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Rob2

You can change the dpi setting using OSX preview.

guilleface

thanks, one more thing and that all my actors need to be place at a exact even number like 10 or 11 instead of 10.45564? will be hard to change all actors position too on all levels again.

gyroscope

I'm afraid so; you soon get used to it though, adjusting the position so it's "pixel-perfect" when you first go into the actor's rules. THose that don't have rules, if you've a lot, I can see it'd be pain.... :-(

SlickZero

Are you talking about actors on the stage in GameSalad? If so, they can be anywhere. You don't HAVE to change their positions unless you want to, or they get shifted from resizing the images. But positions on the stage don't have to be an exact even number…Unless you are making a grid of some sorts...

guilleface

yeah i was talking on the scene, like say i place my scores actors at 200.93838 so thats ok?

SlickZero

That's absolutely fine if that placement works for you.

gyroscope

Hi SZ, interesting: I've always believed the opposite. My reasoning is that if the actor is not on a perfect pixel number, it'd blur slightly (if it's a static actor in particular)... I'm not doubting what you're saying but can you absolutely confirm it doesn't matter?

SlickZero

Hey gyro. As a matter of fact, I don't have official confirmation on that.

Although, testing my own games with the positioning, (and using proper dimensions for the art) I haven't seen a change in quality on the device going from an even number to a number with a decimal suffix.

SAZ_1

In terms of quality of art i dont think it blurs them out or to a noticeable difference, but if actors are colliding etc. it can have an effect, well it has to me any ways, sometimes they wouldn't register the collide properly or overlapping etc... but as gyro said ive always thought the same that thing should be pixel perfect, just makes things seem more neat!

coojam

Just so you know, 72dpi is a design standard that is used across all screen-based graphics, regardless of application or implementation. No idea what the conversion to dpcm would even be!

For future reference, the standards are:
Graphics for screen = 72dpi
Graphics for print = 300dpi (this won't be relevant for anything you do in GS)

gyroscope

Spot on @coojam, and just to add about graphics for print, 300dpi is the optimum top quality printing for colour, any higher won't make any difference (in fact might make it worse). So 300dpi is the print equivalent of iDevice retina display! Also 250dpi is acceptable and in the main there is no discernible loss of quality in a lot of cases, with difficulty in making out a difference between that and 300dpi.

Clouds

@guilleface

"i just search the forum and find out that my images need to be 72 pixels/inch, but i think I'm being doing all my images at pixels/cm, so do i have to redo all my images again? is this why my circles look like oval on a device?"

No, whether your image is 72 ppi or 72ppcm (or 4,000,000 ppi for that matter) will not effect the aspect ratio.

Clouds

@cooljam

Just so you know, 72dpi is a design standard that is used across all screen-based graphics, regardless of application or implementation. No idea what the conversion to dpcm would even be!

28.34 ppcm

Clouds

@gyroscope

300dpi is the optimum top quality printing for colour, any higher won't make any difference (in fact might make it worse).

You mean 300 ppi (rather than 300 dpi) ?

I would say the opposite is true to what you say here, 300 ppi is the *minimum* acceptable quality for modern offset litho as even cheap magazine print is 150 dpi (300 ppi / Nyquist frequency = 150 dpi)

If you are printing above 150 dpi (very common) then you will need more than 300 ppi to avoid aliasing, it's not unusual to work at 400 ppi upwards.

How do you think having more resolution would make things worse ?

gyroscope

Hi Tynan,

"You mean 300 ppi (rather than 300 dpi) ?"

No I mean 300 dots per inch as we were talking about printing. I don't know about Nyquist frequency, and never heard it in all the years I was a professional graphic designer dealing with print companies on a daily basis, Ill have to check that out. 300 dots per inch because if you look under a glass at a magazine you'll see the physical dots printed, 300 of them every inch. 300 pixels per inch is precisely equivalent to 300 dots per inch except a computer screen can only show 72ppi as you know, no matter what the resolution of the image is.

So 300ppi will print as 300 dpi. I've never heard of printing higher than 300dpi (4 colour printing) and even if people do, there will be no difference visually in quality between 300dpi and anything higher simply because the human eye can't detect any more detail.

Printing at higher than 300dpi (litho) might make things worse in some cases, because it will oversaturate the paper, even a high gloss one.

As you say, printing from higher than 150ppi from the computer (equivalent to 150dpi on paper) is common because the higher the ppi/dpi, the higher the quality is, of course; the maximum quality discernible to the eye being 300 dpi. You can print in more than 4 colours though as I'm sure you know, adding spot colours to the CMYK inks, or all spot colours; I guess there's no limit there.

Added: P.s Without checking, I've a vague memory/thought that Nyquist frequency has something to do with B&W halftone screens? You had to watch out for moiré patterns there for certain.

PPS I'm not trying to be clever, just trying to get things right in my head: you mentioned avoiding anti-aliasing, this I don't understand in the print sense; maybe you meant avoiding moiré patterns?