Perceptually Accurate Display of Two Grayscale Images as a Single Color Image

摘要

Life scientists often desire to display the signal from two different molecular probes as a single color image, so as to convey information about the probes relative concentrations as well as their spatial co-relationship. Traditionally, such color images are created through a merge display, where each grayscale signal is assigned to different channels of an RGB color image. However, human perception of color and grayscale intensity is not equivalent. Thus, a merged image display conveys to the typical viewer only a subset of the absolute and relative intensity information present in and between two grayscale images. The Commission Internationale de l’Eclairage L*a*b* color space (CIELAB) has been designed to specify colors according to the perceptually defined quantities of hue (perceived color) and luminosity (perceived brightness). Here, we use the CIELAB color space to encode two dimensions of information about two grayscale images within these two perceptual dimensions of a single color image. We term our method a Perceptually Uniform Projection (PUP) display and show using biological image examples how these displays convey more information about two grayscale signals than comparable RGB color space based techniques.Lay AbstractIt is often useful to display the fluorescent signal from two different molecular probes as a single color image so that information about the probes’ relative concentrations as well as their spatial co-relationship can be visualized. A common way to accomplish this effect is to assign each grayscale signal to a different channel of an RGB color image. However, this method fails to convey much of the information about the two grayscale images, because humans’ perception of color and monochrome values is not equivalent. We have used the Commission Internationale de l’Eclairage L*a*b* color space (CIELAB) to display two grayscale images as a single color image. Our method encodes two dimensions information about the grayscale images as two, perceptually independent and uniform quantities - hue and luminosity - in the color image. Our technique, which we termed a perceptually uniform projection (PUP) display, conveys more information about two grayscale signals than comparable RGB color space based techniques. We apply this method to display several types of information commonly encountered in cell biology images.