Configuring Eye of Gnome

You can set the configuration options for Eye of Gnome by using the Preferences dialog. You can access it with the Settings->Preferences... command on the main menu. This chapter describes the different options that you can set.

Display Preferences

The first page of the Preferences dialog is for the display configuration; it is shown in Figure 1.

Figure 1. Display Preferences

Interpolation type

This option lets you set the interpolation method that Eye of Gnome will use when scaling images. When zooming into an image you can choose to look at the big rectangular pixels or to look at a smoothed-out version; when zooming out you can look at a low-quality version of the image or at a higher-quality rendering.

Normally you want to leave interpolation turned on, because most photographic images look better that way. You may want to turn it off if you are zooming into very low-resolution computer images such as icons.

Nearest neighbor. This means use no interpolation. Pixels will be replicated for zooming in and you will see fat rectangles. When zooming down, the image will lose a lot of detail and possibly look odd.

Bilinear. This a simple and very fast interpolation method. When zooming in, up to four adjacent pixels will be taken into account to compute the color of a new pixel. When zooming out, regions of the original image will be averaged together to compute the colors of the new pixels.

Hyperbolic. This is the highest-quality and slowest interpolation method. It does interpolation as described by George Wolberg in Digital Image Warping.

Transparency type

This tells Eye of Gnome how to render the background for images that have partially opaque regions. It is customary to overlay the image on a checkerboard so that you can clearly see which areas are partially opaque or fully transparent. However, you may also want to overlay the image over a solid background so that you can see it without any visual distractions.

Dark checks. Makes checks consisting of alternating black and dark gray squares.

Midtone checks. Makes checks consisting of alternating dark and light gray squares.

Light checks. Makes checks consisting of alternating light gray and white squares.

Black only / Gray only / White only. These options create a solid-colored background for the image.

Check size

This option specifies the size of the checks used as a background for images that have partially opaque regions. This is mostly a matter of personal preference or gratuitous configurability, depending on the way you see it.

Dither type

This option specifies which dithering method to use. In Eye of Gnome dithering consists of simulating more colors than your display can actually handle by clustering together pixels of different colors in the hope that your brain will do its thing and blend them together. You may want to turn on dithering if you are seeing color banding in your images instead of smooth color transitions in the shaded areas of your images.

None. This specifies no dithering, so Eye of Gnome will make every pixel be the closest color to the one in the original image.

Normal (pseudocolor). With this option set, dithering will only be performed on pseudocolor displays. These are displays that use a limited palette of colors to display images, such as cheap or old video hardware with only 256 simultaneous colors. If you have such a thing, well, you should really get a better display. You have no idea of what you are missing.

Maximum (high color). This will perform dithering even on high color displays, even though they have a pretty good quality even without dithering. High color displays are present in medium-end video hardware or many laptops that can display 65,536 simultaneous colors. [1] This will make high-color displays be almost indistinguishable from a true color display (true color displays are the ones with millions of simultaneous colors. If you are really neurotic and are dying to know, the exact number is 16,777,216).

Two-pass scrolling

Eye of Gnome has a nifty feature that can make scrolling look faster when it really is not. It can do this by drawing the images in two steps: the first step renders a low-quality version of the image very quickly, and the second step does a full-quality render. The idea is that you will get better visual continuity even though the program cannot keep up with your obsessively-fast scrolling; you will see the low-quality version almost instantaneously and the high-quality version will magically appear over the quick version.

Some people think this is annoying, though, and they may want to turn this option off. They are the kind of people that balk at the though of eating curried tuna fish and other delicate and subtle things in life. Still, we have to cater to them, so we do.

Notes

[1]

Some even cheaper hardware can display only 32,768 colors. To make sure, you just have to count them.