Loaded Image Doesn't Retain Separate Colors in MATLAB

0
votes

I have an image of a map loaded in MATLAB.

BEFORE the map is loaded into MATLAB the appearance is:

US Continent: Green

Ocean: Blue

Canada: Yellow

AFTER I load the map it is displaying:

Canada and the US as one color BUT I need to separate them by colors.

My code is:

im = double(imread('US.png'))
figure;
colormap summer;
...
1
imagematlab
Does removing colormap summer not fix this? – mathematician1975
Nope. On a gray scale it makes Canada and US white. – Minimalist
Did you check the actual values of im once loaded? Do these correspond to the three (pure) color values you see before loading (red, green, blue)? Do they give 3 distinct values after rgb2gray? If yes, then maybe your problem is with scaling the displayed image. – gevang

1 Answers

0
votes

As a rough guess, I'm assuming you are not properly scaling your intensity (color) values, i.e. not in [0, 1], so any value above 1 is mapped by the colormap (any color or grayscale) to the same value.

As long as length(unique(im))==3 (three distinct indices for the three gray-scale values that you see before loading), then both of the following should scale your visual output: 

imshow(im, []); colormap summer;
imshow(im./max(im(:))); colormap summer;