4.12. Warp Transform

Figure 14.155. Warp Transform Tool

Warp Transform Tool

Warp Transform is a GEGL based brush-like tool which replaces the old iWarp filter and works directly on the image, on real things instead of a tiny preview window. You can use an erase mode to partially remove warping you applied. You have available options to adapt strength and size of warping.

4.12.1.  Activating the Tool

There are different possibilities to activate the tool:

  • from the image-menu: ToolsTransformWarp Transform,

  • by clicking the tool icon in toolbox: ,

  • or by clicking on the W keyboard shortcut.

4.12.2. Options

Figure 14.156. Warp Tool options

Warp Tool options

The available tool options can be accessed by double clicking the Warp Transform tool icon in toolbox.

Interpolation
[Note] Note

An interpolation method is used during warping. See Interpolation for a description of these methods.

Move pixels

Move pixels is the first item of a drop-down list which contains various warping methods:

  • Move pixels is the default method.

    Figure 14.157. Move pixels example

    Move pixels example

  • Grow

    Figure 14.158. Grow example

    Grow example

  • Shrink

    Figure 14.159. Shrink example

    Shrink example

    Clicking 5 times at the center of the image with brush size = image size.


  • Swirl clockwise/counter-clockwise

    Figure 14.160. Swirl example

    Swirl example

    Swirling clockwise the whole image (brush size = image size) with a circular movement of the brush.


Adapting Size, Hardness, Strength, Spacing

  • Size : the size of the brush is increased.

  • Hardness : TODO (work in progress).

  • Strength: set displacement of pixels during warping. The maximum of displacement is on the brush diameter.

  • Spacing : TODO (work in progress)

Abyss policy

Abyss is a term used by GIMP developers for data outside the input buffer. The warp tool moves pixels from one point to another. Some pixels may come from outside the layer boundary. These pixels don't actually exist anywhere, and therefore don't have any associated color; yet, some color must be assigned to them.

Abyss policy has a drop-down list that allows you to fill empty areas in different manners:

  • None: this is the default option. Empty areas are transparent. An alpha layer is necessary for this option.

  • Clamp: each edge of the transformed layer stretches out indefinitely, so, for example, a pixel to the left of the layer boundary has the same color as the leftmost pixel of the layer with the same y coordinate. An alternative way to think of it is that each pixel outside the layer boundary has the same color as the closest pixel inside the layer boundary.

  • Loop: the transformed layer repeats itself in all directions, so that, for example, falling off the right edge of the layer takes you back to the left edge.

  • Black, White>: these options are similar to "none", but use black and white for out-of-bounds pixels, instead of transparency.

Figure 14.161. Examples for Abyss policy options

Examples for Abyss policy options

High quality preview

preview is the image window, where you work, before pressing Enter to validate the transformation. With this option checked, preview is more accurate, but slower.

Stroke

TODO (work in progress)

Animate

This option allows you to generate several intermediate images between the original image and the final deformation of this image.

Frames to set the number of frames in this animation.

Create Animation button: to create the animation. A new image window is created. Export it as a GIF image, checking the As animation option in the export dialog.