creating shapes

[ChristianWeeks]

Alright I have several questions but they're fairly straightforward.

First is using the shapes tool. Technically, I dont even really need to use the shapes (as of right now), I just need to make a straight line. So I use the shapes tool to make a straight line. Every time I do this, though, it creates a completely new layer that contains ONLY that line. How the hell can I just create a simple straight line on an already existing layer?

I didnt think creating a straight horizon line could be so difficult. : /

Ok, second thing is i wanted to know how (if you can) I can the colors of a picture. The pic I've got in mind is just a black and white outline of a city skyline, and I want to make it at night, which would mean the majority of the pic should be dark. So all i want to do is reverse it so that the black outline is white and the whole rest of the picture is black.

Any responses would be much appreciated. Particularly on the first question, that ones gotten me real frustrated.

[Smashed_Pumpkin]

On the paintbrush tool just click where you want the start point of the line, then while hold shift and click where you want the end point and it will draw a line between the two.

(Shift clicking pretty much draws a line from the point at which the paintbrush last left the page to the point you are clicking. So you could draw a curve freehand, let go of the button, hold shift and then click somewhere to make a straight line from the end of the curve to that point)

[Elwell]

First is using the shapes tool. Technically, I dont even really need to use the shapes (as of right now), I just need to make a straight line. So I use the shapes tool to make a straight line. Every time I do this, though, it creates a completely new layer that contains ONLY that line. How the hell can I just create a simple straight line on an already existing layer?

On the toolbar, there are three icons at the left: A square with four little squares at the corners (shape layers), the same with a pen inside it (paths), and a plain square (fill pixels). You want to make sure the last one is selected, then the line tool will do exactly what you want it to.

[Blaise]

For the second quiestion - Just go to menu items Image>Adjustments>Invert