Pixen draws a background behind transparent pixels in the canvas. By default, it is a slashed pattern, however you can customize it to your liking.
To get started, open the Window menu and select Backgrounds Library. Here, you can browse the system backgrounds and create new ones.
To create a new background, click the + button, and select a starting template from Flat, Checkerboard, Slashed, or Image types. You can then customize the colors of each background type. For the image-based template, you can choose an image and customize how it's drawn such as whether the image should be scaled with smoothing. You can also pick a resize mode such as Stretch, Fit, or Cover. The image template is particularly useful for setting reference images.
From the Backgrounds Library, you can also delete backgrounds by right-clicking on a background and selecting the Delete command. You can rename backgrounds by using the Rename command from the context menu. You can use the Edit command to edit a background. Note that the four default system backgrounds cannot be edited.
If you'd like to export a background to disk, you can do so with the Export command. Similarly, the Share context menu option can be used to share backgrounds with others using the system share sheet. If you'd like to import a
pxbgnd file from disk, simply double-click it in the Finder or drag it into the Backgrounds Library window.
If you would like to set a background as the default background for documents going forward, you can right-click on it and select Set as Default Main Background. To reset the default background, click the More button and select Reset Default Main Background.
Now that you've created some backgrounds, you can apply them to your documents. To do so, click the Set Background command in the View menu or use the Background button in Pixen's main toolbar. All the backgrounds from the Backgrounds Library will be visible so you can select one to use with the current document.
To learn more about Pixen or purchase the app, visit https://pixenapp.com.