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.
#1
I'd say that the image is encoded from the top left. Like the way you would write on a page.
#2
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
#3
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.
#4
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.
#5
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 :-)
#6
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.
#7
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.
#8
FreeHand?
#9
Every version of BASIC I've used uses the same system, unless you explicitly tell it not to. Also true of Windows Paint.
#10
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.
#11
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!
#12
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
#13