Two images of the same spiral galaxy are shown in Fig. The left panel shows the familiar image that you would see
if you took a picture of the galaxy through a single filter. The image on the right shows the "negative" (or "inverse")
of the image on the left. The negative image has been altered so that dim parts of the original image are now
white, and bright parts are now dark.
How can I make filter using MATLAB code the RGB galaxy image to be like that image??
I tried this code but it does not give me what I want -- the result image is not clear.
positiveImage = imread('PGC0020886.png');
negativeImage = 255 - positiveImage;
a = imread('PGC0002440.png');