Add Slice tool information

drawing.md

@@ -24,6 +24,8 @@ Other tools that will help you in the drawing process:
 * ![Eyedropper tool icon](tools/eyedropper-tool.png) [Eyedropper](eyedropper.md) (`Alt` or `I` key)
 * ![Selection tool icon](tools/marquee-tool.png) [Rectangular Marquee](selecting.md) (`M` key)
 * ![Move tool icon](tools/move-tool.png) [Move Cel](move-tool.md) (`Ctrl` or `⌘` or `V` key)
+* ![Slice tool icon](tools/slice-tool.png) [Slice](slices.md) (`Shift+C` key)
+
 
 ---
 

slices.md

@@ -0,0 +1,62 @@
+# Slices
+
+With the Slice tool ![Slice tool icon](tools/slice-tool.png) you can
+indicate regions of your sprite and assign a name/label to that region
+with some extra user defined information. There is support to specify
+[9-slices](https://en.wikipedia.org/wiki/9-slice_scaling)/9-patches
+information.
+
+With this tool you can:
+
+1. Create a new slice marking a rectangular region pressing the mouse
+   button, dragging the mouse, and releasing the button.
+1. If the marked rectangle touches existing slices, those slices will
+   be selected.
+1. You can drag-and-drop a set of selected slices to move them to
+   other place. Or you can resize the whole set of slices dragging
+   from the corners or edges.
+1. After selecting some slices you can delete them pressing the Delete
+   key or *Edit > Delete* menu option.
+1. Double-clicking a slice you will see the [Slice
+   Properties](#slice-properties) dialog.
+
+## Slice Properties
+
+If you double-click a slice, you will see its properties:
+
+![Slice Properties Dialog](slices/properties.png)
+
+Here you can specify:
+
+1. the bounds of the slice in the canvas
+1. a 9-slices property to specify an internal rectangle to sub-divide the bounds into sub-slices
+1. a pivot to specify the central/base location of the sprite inside the slice
+
+## Exporting Slices
+
+You can export each slice as a different sprite using the
+[--split-slice option](cli.md/#split-slices).
+
+You can also export the slice information in a sprite sheet JSON using
+the [--data option](cli.md/#data)) or the *File > Export Sprite Sheet*
+menu option with the JSON output checked. This is an example of the exported data:
+
+```json
+{ ...
+ "meta": {
+  ...
+  "slices": [
+   { "name": "Button-patch",
+     "color": "#0000ffff",
+     "keys": [{ "frame": 0,
+                "bounds": {"x": 118, "y": 118, "w": 20, "h": 21 },
+                "center": {"x": 5, "y": 5, "w": 10, "h": 9 } }] }
+  ]
+}
+```
+
+---
+
+**SEE ALSO**
+
+[Drawing](drawing.md)