This command allows you to specify an image (BMP, GIF, JPG, PNG, or TIF) that will be drawn within the plot extents. The image will be stretched to fill the plot exents, regardless of its width/height relative to the plot width/height. To delete an existing background, delete the text in the Filename text box.
Use full extents of image
If checked, the entire image will be used. If unchecked you may specify the top-down coordinates (0 is at the top of the image, in other words) of the image to display. The left, top, right, bottom text boxes will be disabled until/unless you select an image. Valid values are 0 to width-1 for the left and right; 0 to height-1 for the top and bottom. The left value must be less than the right, and the top value must be less than the bottom.
Force plot extents to match aspect ratio of image
If checked then the plot extents will be adjusted such that the image has a 1:1 pixel ratio. For example if the image is 800 x 600 pixels and this box is checked, then the width and height of the plot will be set to a 4:3 ratio. If "Specify plot size" was previously selected and the current settings do not match the image aspect ratio, then the maximum dimension will be used for the larger of the width/height. If "Specify plot size" has not been previously selected then the maximum dimension will be set to 8 inches. This adjustment takes place at the time this command is used and is not persistent: Subsequently changing the plot size with the Extents/Intervals/Size menu command or by dragging the corners of the plot may result in a distorted background image. (If you do this unintentionally, you can easily restore the plot aspect ratio by again selecting the Background Image command and immediately clicking OK w/o making any other changes.)
Draw in foreground
If unchecked then the image is drawn before any other items. If checked then the image is drawn after all other items.
Global transparency value applied to entire image. Valid range is 0 (invisible) to 255 (opaque). Default value = 255 (opaque).
Color that will not be drawn. This setting is disabled for 32-bit images with an alpha channel.
Example: GPS recording with a background image from Google Earth.
This feature can also of course be used to fill the background with a gradient. The example below uses a 1-pixel wide background image, with Force plot extents to match aspect ratio of image unchecked.
Related macro commands