The colors that can be distinguished by human eyes are much more than the gray levels that can be distinguished. More objects information of the gray image can be obtained through the pseudo-color processing. In a fundamental departure from the current pseudo-color processing methods, quantitative metrics for human visual detection and recognition were devised to measure perceivable objects information after pseudo-color processing, and a pseudo-color processing method was proposed under the metrics. At first, it was ensured that different gray levels were mapped to distinguishable colors. Then, a gray-to-color mapping function was created to make more objects information be perceived. In the comparison experiments, the proposed method can make more objects noticed by people. The proposed method can process images in real time.