*Chromostereopsis*

The chromostereoptic effect is complex and its effects can vary due to many different reasons. Nevertheless, for simple images and in a dark background, red objects tend to appear closer to the observer than blue objects, as can be seen in Figure 12. There, the red and blue stripes will seem to be in separated depth levels for most observers, with the red being apparently nearer to the observer.

**Figure 12.** Red and blue stripes on top of a dark background. The red stripes tend to be seen as being nearer by most people.

This can be extrapolated to warm and cool colors, since, in general (and always when in a black background) warm colors come forward and cool colors retreat [16,19]. However, in [20] researches have also proved that, when the background is white, the effect is reversed, and the warm color seems to be further away than the cool one, as can be seen in Figure 13, which sets the same blue and red colored image to both a black and white background.

**Figure 13.** A white background inverts the effect of chromostereopsis. In the top image, most people would see the red color as receding into the distance and the blue nearer to the viewer, while in the bottom image it will mostly be seen as nearer than the blue color.

An algorithm for conveying the chromostereoptic effect in simple images through temperature cues will be presented. However, first it is necessary to find out why some of these colors seem to recede or advance when in company with other colors. Even though warm colors tend to be felt nearer and cool colors tend to be felt further away, that is not always the effect produced. It seems that the most important features for this chromostereoptic effect in simple images are luminance and saturation.
