Re: [Gimp-user] Restricting tool movement along a single axis

[scl <scl gplus gmail com>]

On 3.11.2013 at 1:24 PM alemelo wrote:

> Hello,
> [...]  I want to be able
> to pick a corner - say the bottom right one - and move it *only* right or left,
> without any vertical shift.
>
> I tried with guidelines but I cannot make them stick to the exact side of the
> image neither if I tell GIMP they're magnetic.
> But what's worst is that even if I manually put guides along the edge, it seems
> that the corners of the perspective tool ignore completely the magnetic
> attribute.
>
> In Photoshop I could simply pick one corner, hold the shift key and restrict
> movement to the two main axes.
>
> Any analog trick in GIMP?

In GIMP there's a similar trick for the Move tool: use the arrow keys to
move the layer horizontally or vertically. If you press Shift+Arrow keys
the movement is in bigger steps (ca. 25 display pixels) -> depending on
zoom level you can move across the image in smaller or bigger steps.

Unfortunately the arrow key method has some flaws:

1. It can only move the active layer. Picking up a layer doesn't work,
because the Shift key is double-bound to 'Tool toggle' and 'Move in
bigger steps'. At the end 'Move in bigger steps' wins. Using the mouse
to select a layer and the arrow keys to move precisely doesn't work.

2. Moving the currently selected guide doesn't work. Instead the active
layer is moved.

3. The arrow keys don't support precise application of the
Transform Tools consistently:
- Crop Tool: only move the crop area around if it was moved with the
mouse before.
- Rotate Tool: rotate in steps of 15 degrees, the same way as using
Shift+Arrow keys or Ctrl+Mouse
- Scale, Shear: up/down arrow keys in-/decrease the value of the 
selected input field (width, height, shear magnitude)
- Perspective Tool, Unified Transform Tool (in GIMP master): no function.

As described in another posting the magnetic rulers have the effect
to let the mouse cursor snap in at the ruler, not the center of the
handler what can be a bit unpredictable and thus unprecise. I could
reproduce this with all Transform Tools except the Move and Crop tools.

Kind regards,

Sven