Lesson 10: Canvas tools for measurements and positioning

The grid

Your image has a grid "underneath", to help you for precise positioning and alignment. Its visibility can be set on/off via the toggle command View > Show Grid. With Edit > Preferences > Image Windows > Appearance you can set if you want the grid shown by default for the Normal Mode and/or for the Fullscreen Mode. With Edit > Preferences > Default Grid you can set all the properties of the Grid: line style, color, spacing, and offset. So with all these options, the Grid is under your control absolutely.

Still beyond the general properties of the grid, if you want to set the grid properties specifically for the image you work on, you can go with Image > Configure Grid...

With the toggle command View > Snap to grid you can set if you want your pointer to snap on the grid, which can be very useful when drawing. This stays active even if you are not showing the grid. The snapping distance is configured with Edit > Preferences > Tool Options > Guide & Grid Snapping, where you can control the distance under which guide and grid snapping activates.

These options for the grid, together with zooming in (remember the shortcut: CTRL+Wheel), and using guides, and keeping an eye to the pointer coordinates down left at the statusbar, all these tools help you much to work with absolute precision on the canvas.

The guides

We have seen them in lesson 2. I just want to add one command that resides under the "Guides" submenu: Image > Guides > New Guide from Selection. With this you get four guides, one for every extreme point of your current selection. Note that the guides do not go on the marching ants, but this seems to work as expected on a non-continuous tone selection.

The Pointer dialog: a very useful sampling tool

This is one more dockable dialog in the GIMP's interface. It offers you - in absolutely real time, anytime - valuable information about the position of your pointer, the position/size of the current selection (if any), and the color of the pixel under your pointer.

• The position of the pointer is expressed a) as x and y coordinates from the origin point of the canvas and b) as distance from that origin in inches.
• As for the selection (if any), the position and the size are referred to the "bounding box" of the selection, which means that it is less useful (but probably still useful) in the case of a "continuous tone selection".
• As for the color under the pointer, you have two options with the same choices, giving you the ability to peek and compare the color components in different color models: you can have the values in RGB as absolute values (0-255), in RGB as percentages, in HSV and even in CMYK. You can also have the color as hex value. Still more, with Sample Merged you can define if GIMP takes into account for the sampling all active layers or just your currently selected layer only.

The Measure Tool

This tool makes you able to measure distances and angles.