The Transform tool can rotate, crop, resize, warp, correct perspective or tile one or more maps simultaneously. Common operations like aligning or straightening a source photo can be easily done with this tool.
Start by opening a map (File Open, Paste, Drag'n'Drop...) in one of the editors.
When you select the Transform tool, the Tiling Preview switch at the bottom of the Editor area enables itself, repeating the image along the borders, for better visualization of its tiling.
Notice the four handles at the corners of the image, with black and white lines connecting them along the image sides.
These handles and lines show the position of the original image rectangle, and allow transform operations to be done by dragging them, with or without pressing Ctrl.
The "This Map - All Maps" switch controls whether changes apply only to the current map or to all open maps.
Click and drag one of the corner handles: the image will rotate around its center.
Now before dragging a corner, press Ctrl: the image will be warped or perspective-corrected, depending on the handle positions and the alignment between the black and white lines.
At the tool controls area, the Outside Fill setting defines what happens to pixels that would be transformed from outside the source image and thus would be undefined. For example what happens to undefined pixels when you rotate an image? In this setting you can set if they should tile as usual (Tiling), do a Mirrored Tiling or clamp to its sides (Edge Clamp).
Try clicking over and dragging a black and white line connecting two handles: the image will resize proportionately with respect to the opposite size. If you resize to a size smaller than the original image size it will tile copies of itself, according to the Outside Fill selection.
But if you drag a black and white line while pressing Ctrl, only the dragged side will move, thereby resizing in a non-proportionate manner.
Back to the tool controls: the Show Grid switch enables displaying of a grid which can be helpful in aligning edges.
Dragging the center of the selection will pan the image. Try dragging it to see what happens.
The Reset Controls button will return the controlling handles to the initial positions at their corners and reset the transformation.
At the bottom of the tool you'll find the Final Size settings that control the effective size of the map, after all transforms applied. The Reset link sets the final size back to the previous values of the map.
By using this and the other operations we've seen, you can do many types of alignment and crop operations with the Transform tool.