Photoshop
Retouching and Editing
Rulers, Grids and Guides
Before we get into the retouching tools and editing commands, we'll go over using rulers, grids, and guides. These are extremely valuable options to assist you in laying out your image content with accuracy.
Rulers
Rulers are displayed along the top and left edges of the image. When your pointer is over the image window, dynamic markers appear on both rulers to show you the cursor location coordinates.
Displaying and Hiding Rulers
To view rulers in an image document, go to View > Show Rulers. The menu command will switch to Hide Rulers which you can use to hide the rulers again.
The keyboard shortcut is Ctrl-R (Cmd-R) to toggle rulers on and off.
Changing Unit of Measurement
The rulers are displayed in pixel units but you can change the unit of measurement by going to Edit > Preferences > Units & Rulers (Photoshop > Preferences > Units & Rulers). Double-clicking on one of the rulers will also open the Units & Rulers preferences.
This will affect the units displayed on the Tool Options bar and in the Info panel (partially shown here). The X and Y cursor coordinates and the W and H (Width and Height) fields use this preference also and will change accordingly. Other dialogs that display dimensions will change to these units as well.
Point of Origin
The point of origin is located at the coordinates 0,0 which normally is at the top left corner of an image document. If you want to measure from another part of the image, you can change the point of origin to another point.
There is a square in the upper left corner of the image document where the two rulers meet. If you click and drag on the corner square, you can drop it in a new location to set a new point of origin as shown here. The cursor will change to a crosshair and dotted lines will extend from the cursor to each ruler and move along with the cursor.
This image shows how the rulers changed after setting a new point of origin. The 0,0 coordinates intersect at another point in the image. Values to the left or above the 0 points are negative values.
To reset the point of origin back to the default, double-click on the corner square.
Guides
Guides are non-printing lines that you can set in an image to help you in aligning your content. They can be horizontal or vertical. You can add, remove, reposition and lock guides to prevent you from accidentally moving them. Guides can be toggled between being displayed and hidden.
Adding Guides
Guides can be added in two ways: by dragging them from the rulers or by setting exact positions for them.
Adding Guides by Dragging
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Rulers must be displayed. If they aren't visible, press Ctrl-R (Cmd-R).
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Do one of the following:
- Click and drag to the right from the vertical ruler to create a vertical guide. (shown at the right)
- Click and drag downwards from the horizontal ruler to create a horizontal guide.
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Hold the Shift key down while dragging to snap the guides to the ticks on the ruler.
Adding Guides Using the New Guide Dialog
With the New Guide dialog, you can set the exact position of your guides. Rulers don't need to be displayed with this method.
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Go to View > New Guide to display the New Guide dialog.
- Select either the Horizontal or Vertical radio button and enter a Position value. If you're using the same unit of measurement that's set in your preferences (in this case, it was set to pixels), you only have to enter a number. You can still enter in another unit of measurement by adding the unit explicitly; for example, "1 in" or "3 cm".
- Click OK to add the guide.
Moving Guides
Guides are repositioned by dragging them with the Move tool. To switch to the Move tool, you can use the shortcut V. To temporarily access the Move tool, hold down the Ctrl (Cmd) key. Once it's positioned over a guide, the pointer will turn into a double-headed arrow 
. Drag the guide to a new position.
Hiding and Displaying Guides
Toggle between hiding and displaying guides by going to View > Show > Guides or use the keyboard shortcut Ctrl-; (Cmd-;).
Locking Guides
Once you've set up guides, you can lock them to prevent you from accidentally moving them by going to View > Lock Guides. To unlock guides, repeat the command.
Removing Guides
Guides can be removed from an image in one of the following ways:
- To remove a single guide, use the Move tool to drag it and drop it onto the ruler or outside the image window.
- To remove all guides in an image, go to View > Clear Guides. This will clear locked guides, too.
Guide Preferences
The appearance of guides can be modified in Edit > Preferences > Grid, Guides & Slices (Photoshop > Preferences > Grid, Guides & Slices). Alternately, double-click a guide with the Move tool to open up the Grid, Guides & Slices preferences.
The following guide preferences will apply to all images containing guides.
- Colour
- You can select from one of the nine colours displayed in the pop-up menu or choose Custom to open the colour picker and select your own colour.
- Style
- Choose between (solid) Lines or Dashed Lines.
Smart Guides
Smart guides help you to align objects and selections. They appear temporarily while you're drawing or moving objects and selections. To turn the visibility of smart guides on or off, go to View > Show > Smart Guides.
In this first example, the top shape is being moved horizontally using the Move tool. When the right edges of the shapes are in alignment as shown here, a smart guide (magenta line) appears. When the centres of both shapes line up, a smart guide will extend between the horizontal centres of each shape. Ditto for the left edges of the shapes.
In this example a selection is being moved vertically. The smart guide appeared when the bottom edges were aligned.
The colour of smart guides can be changed in the Grid, Guides & Slices preferences. Magenta is the default colour.
Grid
The grid is displayed as a network of horizontal and vertical non-printing lines in the image. Like guides, they are used to help you position your content.
Displaying and Hiding the Grid
To toggle between displaying and hiding the grid, go to View > Show > Grid. The keyboard shortcut is Ctrl-' (Cmd-').
Grid Preferences
The appearance of the grid can be modified in Edit > Preferences > Grid, Guides & Slices (Photoshop > Preferences > Grid, Guides & Slices). The preferences will apply to all images.
- Colour
- You can select from one of the nine colours displayed in the pop-up menu or choose Custom to open the colour picker and select your own colour.
- Style
- Choose between Lines, Dashed Lines or Dots.
- Gridline Every
- Gridlines are the bolder lines of the grid. You can set a different distance between gridlines by entering a value. You can change the unit of measurement in the pop-up. One of the options is Percent which lets you divide up an image into even sections.
- Subdivisions
- This sets the number of times the gridline will be subdivided. If gridlines are every one inch and there are four subdivisions, subdivision lines will be one-quarter inch apart.
The Gridlines Every and Subdivisions settings at the right were used to produce the grid in the sample image. With gridlines set to 50 px, with five subdivisions, the subdivision lines are 10 px apart.
Snap
The ability to snap graphic elements and selections to the guides and grid are what makes those options extremely useful. Snapping occurs when you drag something within 8 screen pixels of a guide or grid line. The object will be drawn to the line like to a magnet and will snap against it. You can snap the edges or centre point of an object to a line.
To turn snapping on or off, go to View > Snap.
Below the Snap command, there is a Snap To command that contains a number of options for enabling/disabling snapping in its submenu. A check mark indicates that snapping is turned on. No check mark means snapping is not enabled. Since there were no slices when this screen shot was taken, the Slices command and its check mark are greyed out.
Each Snap To command is described below.
Guides
Selections and graphic elements can be snapped to guides. Likewise, guides can be snapped to selections and graphic elements. When guides are hidden, the snapping behaviour no longer occurs.
In the example at the right, the horizontal centres of three different types of elements were snapped to a vertical guide using the Move tool: a vector circle, a raster flower, and some text.
This example shows how to use guide snapping with a selection marquee to measure out exact distances for placing objects. Our objective was to have two blue circles arranged vertically with exactly 15 px of space between them.
- With the circle layer active, the Move tool was used to snap a guide to the bottom of the circle.
- A rectangular selection marquee measuring 15 px by 15 px was drawn, starting at the guide. You can set the exact dimensions in the Tool Options bar by selecting Fixed Size in the Style drop-down menu. If you draw the marquee away from the guide, you can drag it with the rectangular marquee tool and snap it to the guide.
- Snap another guide to the bottom of the square selection.
- Finally, create a copy of the circle layer and drag it down while holding down the Shift key using the Move tool until it snaps to the lower guide.
When using the Move tool to snap elements to guides, the normal black arrow cursor becomes white when a snapping point is reached. This cursor is shown in step 4.
Grid
Snapping to the grid can be tricky when the grid size is small. In this example, the grid was quite large. The four blue circle outlines have been snapped to various positions around an intersection of grid lines. Since each object has five snappable points (the centre point plus the outer four edges), on a small grid there will be a great deal of snapping as you move the object over the grid lines. When the grid is hidden, no snapping will occur.
Layers
This option will allow you to snap guides to the outer edges and centres of content on the active layer.
Slices
Although slices aren't covered in this course, this option will let you snap objects and selections to the edges of image slices.
Document Bounds
Objects and selections can be snapped to the four edges of the document window. This works whether the rulers are displayed or not. This example shows moving a circle to snap against the top edge. Notice how the cursor changes when a snap point is reached.
All
In the example shown here of the Snap To submenu, All is greyed out. This is because all of the elements in the top part of the submenu have already been enabled. If one or more don't have check marks displayed, the All command will be available. It will enable all the options and display them with check marks.
None
Using this command will disable snapping for all options.
Extras
In the View menu, the Extras command and the Show submenu items are related. In addition to enabling the visibility of guides and the grid, the Show submenu also lets you show/hide selection marquees, the border around a vector shape when it's selected (Target Path), image slices and other non-printing elements that are used to edit images. All of these are referred to as extras.
The Show submenu can be used to enable extras selectively. The Extras command will show/hide all enabled extras at once. In the sample image at the right, there are several extras displayed: slices, a guide, the grid, the snail shape's target path, and a selection marquee. Sometimes the clutter can be distracting and it's helpful to be able to hide these temporarily.
Disabling extras using the Extras command will hide all these extras. To restore visibility, click the command again. Restoring them will only display the extras that were enabled in the Show submenu before you applied the Extras command.
At the bottom of the Show submenu is the Show Extras Options command. It displays the Show Extras Options dialog. Here you can enable the extras that you want to be affected by the Extras command. For example, if you want to exclude selection edges from being hidden, disable Selection Edges in the dialog. You can still hide selection edges using the Show submenu but the Extras command won't turn off the visibility of selections.
Although they don't appear in the Show submenu or the Show Extras Options dialog, the visibility of measuring lines created with the Ruler tool and colour samplers created with the Colour Sampler tool will be toggled with the Extras command.
Rulers, Grids and Guides Summary
- Rulers are displayed along the top and left edges of an image.
- The unit of measurement displayed on the rulers is determined by the Rulers setting in the Units & Rulers Preferences. This setting will also apply to the values displayed in the Tool Options bar, the Info panel and in dialogs that use distance values.
- The point of origin can be moved from its default position. The rulers will display its 0,0 values at the new point of origin.
- To restore the point of origin to its default value, double-click on the top-left corner square when rulers are displayed.
- Guides and the grid are non-printing lines that you can position in your image to assist you in laying out your content.
- Rulers must be displayed to create guides by dragging.
- Horizontal guides are dragged from the top (horizontal) ruler and vertical guides are dragged from the left (vertical) ruler.
- Guides can be positioned precisely using the New Guide dialog.
- Guides are moved by dragging them with the Move tool.
- Use the View > Lock Guides command to lock guides so they can't be inadventently moved.
- To delete a guide, drag it back to the ruler or drag it outside the image window.
- To delete all guides in an image, use the View > Clear Guides command.
- Smart guides, when enabled, are lines that appear temporarily in the image to help align the centres and edges of objects with existing elements in the image.
- The grid is a collection of evenly spaced horizontal and vertical lines that cover an image.
- When Snap is enabled, you can snap objects or selections to guides, the grid, layers, slices and document bounds. Likewise, you can snap guides to objects or selections.
- The edges and centre points of objects and selections can be snapped.
- The Show submenu is used to hide/show non-printing extras in an image.
- The Extras command will toggle the visibility of all extras enabled in the Show submenu unless they have been disabled in the Show Extras Options dialog.
Rulers, Grids and Guides Keyboard Shortcuts:
- Show/hide rulers: Ctrl-R (Cmd-R)
- Temporarily access Move Tool: Ctrl (Cmd)
- Snap guides to ruler ticks when using the Move tool: Shift
- Show/Hide Guides: Ctrl-; (Cmd-;)
- Show/Hide Grid: Ctrl-' (Cmd-')
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