Photoshop’s X and Y Axis

RA
Posted By
Richard_Archer-Jones
Apr 28, 2005
Views
2542
Replies
12
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Closed
One thing that’s confused me for sometime with Photoshop is it’s axis designations. I mean, when moving an object along its X and Y axis I can never remember which way the minus numbers and the plus numbers move an object. Where have they got their ideas from on this? It’s actually only the Y axis that I think they’ve got wrong. I’ve always understood that on a graph the plus numbers are above the horizontal line (the X axis or zero on the Y axis) and the minus numbers are below. So therefore if I want to move an object along the Y axis and type in a minus number my object should go down, but it does not, it goes up. Why is this? It’s most confusing.

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Pierre_Courtejoie
Apr 28, 2005
I’d say that the image is encoded from the top left. Like the way you would write on a page.
SA
sm_adelhoff
Apr 28, 2005
I’d say that the image is encoded from the top left

Whereas a mathematical diagram usually starts bottom left. Maybe that causes the confusion

Sven
RA
Richard_Archer-Jones
Apr 28, 2005
The thing is, if you’re calling them the X and Y values you should follow the recognised rules that govern those values, unless they have different rules for these values in different countries? But I doubt that, otherwise that would cause great confusion.
JJ
John Joslin
Apr 28, 2005
You can put the origin where you like.

Hold the mouse cursor in the top left corner and drag the origin.

Double-click to reset.
RA
Richard_Archer-Jones
Apr 28, 2005
But it shouldn’t make any difference where the origin is (thanks for the double click for reset, didn’t realise that). A minus figure should always take you down in the Y axis regardless of where your zero is. This shows the recognised X and Y axis definitions:-

<http://www.dummies.com/WileyCDA/DummiesArticle/id-1202.html>

Sorry it’s a ‘.. for Dummies’ reference. No offense intended 🙂
P
Phosphor
Apr 28, 2005
There’s been some recent debate about this regarding Illustrator’s use of the Cartesian coordinate system as well.
"X and Y Co-ordinates" <http://www.adobeforums.com/cgi-bin/webx?128@@.3bb9f249>

Personally, I’ve never really had any problems switching my brain back and forth between the way Illustrator does it and the way Photoshop does it. But I’m kinda weird like that.
JB
Jonathan_Balza
Apr 28, 2005
Macromedia Flash also uses that PS’s method of +/- on the Y axis.

I’ve run across this method of using the y-axis before, but I can’t seem to recall offhand where.
JJ
John Joslin
Apr 28, 2005
FreeHand?
JR
John_R_Nielsen
Apr 29, 2005
Every version of BASIC I’ve used uses the same system, unless you explicitly tell it not to. Also true of Windows Paint.
RA
Richard_Archer-Jones
May 4, 2005
But isn’t it a definition of the X and Y axis that down is negative? Isn’t it like deciding to change the north, south, east and west definitions and producing a mapping programme with the Arctic designated as the south pole?

I can only imagine it was a mistake.
D
deebs
May 4, 2005
Ah – Maths 101? Co-ordinate transformations, orthogonality, orthogonal spaces… It all floods back.

Now why should co-ord axes be at right angles?

Ans: because a change in one axis does not force a change in the other.

Suppose the Y axis is at 45 degrees to the X axis. A small change in one induces a small change in the other where small change happens parallel to one axis.

How does this help?
Ans: I dunno but it sure is great!
D
deebs
May 4, 2005
ps – it makes sense to have one set of co-ords located centrally.

It allows (X, Y) values (+, +), (+, -), (-, +) and (-, -)

This will help with co-ord transforms for example to polar co-ords.

Are polar co-ords important?
Yep ‘fraid so for things like ripples and reflections around the origin

in haste

deebs

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