The main image window has many options you can customize. The most common thing that you might want to turn on is to show the rulers on the x and y axis. This will show you rulers spanning the top and left-hand side of the window. The measurement that the ruler is shown in will be set in pixels by default, but can be edited by going to Pixelmator | Preferences | Rulers. Here set the default ruler units to Pixels, Inches, Centimeters, Millimeters, Points, Picas, or Percent. You can use the Command + R shortcut to toggle on and off with the ruler view.

Turning on or off the Rulers option (as well as any other options for the main image window) can all be accessed in the View menu or with keyboard shortcuts.

Another option that can be helpful is the grid view. You can show a grid overlay on the image, which can be very helpful when alighting items. The keyboard shortcut to show the grid view is Alt + Command + '. The following screenshot is an example of what the default grid lines look like over an image:

The gridlines can also be customized in the main preferences screen by navigating to Pixelmator | Preferences | Rulers. You are able to set the color of the gridlines and the number of pixels between the gridlines and subdivisions.

Guides are another very helpful viewing option, especially when you are trying to create a page layout or a collage with many images and need to alight them in a certain way. Guides are easy to create, but first make sure you have them turned on by going to View | Guides | Show Guides or using the keyboard shortcut Alt + Command + ;. Once you have the view turned on, you can add as many guides as you need by simply clicking and holding down the mouse then dragging from the left-hand side or top edge where the ruler is. As you drag your mouse along, you will see a counter showing exactly where you are on the ruler and the blue guide line. In the following screenshot, you can see how the guidelines show up on your canvas:

Release the mouse to place the guide. If you ever need to move a guide, you can always move it later. Moving a guideline is easy, move your mouse over the guideline and then click-and-drag to reposition it anywhere on the canvas.

There are also a few other settings for guides that can be very helpful. These are all located at View | Guides. The first option in this menu is called Show Guides at Object Center. This is very helpful when trying to position an image in the very center of the document. Once it's turned on and you are going to move any layer, you will see a blue guideline appear when the center of that layer is in the center of the overall canvas or the center of any other layers on the canvas.

You can also turn on the option to Show Guides at Object Edges.

The Guides menu has two additional items you can turn on. The first option is Show relative spacing. This option only works when you have three or more objects that are lined up on the canvas. Say you are trying to line up three images to be printed in one large horizontal photo and you want equal spacing between the three photos. When you move one image so that it's equal in distance compared to the two other images, a purple object spacing guide will show you the distance between the images in the current ruler unit that you are using.

In this image, you can see that the images have an equal spacing in between them by using the relative spacing option:

The last option in the guide's menu is to show relative sizing. When this option is checked and you are transforming the size of an image, you will see a purple sizing guide appear when the height and width are the same for both images.

In the following screenshot, you can see that the two images on the left-hand side of the canvas are of the same exact size:

Using rulers, grids, and guides will help you save a lot of time getting different layers positioned just right and also help you edit layouts with precision. You can also change the default color of the guides and object spacing by navigating to Pixelmator | Preferences and accessing the Ruler Preferences menu to choose your own color from the color picker instead of the default blue and purple that Pixelmator sets.

One very important menu is at the very top of the image window on the left-hand side. Here you will see a gear icon that is clickable and shows additional options for the tool that you have selected. I'll refer to this menu throughout the book as the tool settings menu. With this tool settings menu, you will see context-sensitive settings based on the tool that you are currently using. Whenever you first use a tool, it's a good practice to view what options are available for that tool under this settings menu.

Also, on the top of the image window you will have a list of other options spanning across the top. These options will be different depending on the tool you are currently in. For example, if you are using the crop tool, you will see options to constrain the proportions of the crop; and if you are using the Paint Bucket tool, you will see options to pick your color and also the blend options for the tool.

You can turn this on and off by navigating to the Show/Hide Tool options in the View menu.

There is also an info bar that is shown right below the tools options at the top of the main image window. This can also be turned on/off in the Show/Hide Info Bar options in the View menu. Once you turn this bar on, you can also customize what shows up on this by Control + clicking in this area to bring up a list of options you can turn on or off.

The Tools pane is one of the most important menu bars that you constantly use. Here you will see 28 different tools that Pixelmator has. We will cover the details on many of these tools later on in this book. To add or remove tools from this menu, navigate to Pixelmator | Preferences | Tools. From here you can drag additional tools into the toolbar or drag any of them you don't need outside of the toolbar.

Before we get into using some of the tools and making adjustments, one of the most commonly used keyboard shortcuts that you will use is the Command + Z shortcut to undo your last action. You can continue using the Command + Z shortcut to go back as many steps as you need. There is also a redo shortcut at Shift + Command + Z.