Heatmap image convert to data. Percentage of black to white.

Hi,

Im having some issue to find a tutorial which i can change the heatmap from my analysis to percentage. For the image convertion to black and white image, there a lot of tutorial but to anaylze the heapmap i couldnt find any. Im new to this matlab.

Original image.

Need to convert to black and white image as below

Then calculate the percentage of the ratio between black/white region. This is to analyze to heatmap.

thanks.

[Benoit Espinola]

How do you load your image? What is the format in Matlab?

[muhammad afiq]

Im not load yet to the matlab but my image in .png format

Answer 1

[Ameer Hamza]

rgb2gray() seems to work

img = im2double(imread('image.png'));
img_gray = rgb2gray(img);
imshow(img_gray)

However, the correct solution depends on the values of color in the heatmap. Do you have such mapping?

[muhammad afiq]

this is the actual value indication.

[Ameer Hamza]

Do you only have data as an image, or do you also have data in numeric format?

Answer 2

[Benoit Espinola]

You can calculate the lightness (=brightness) of each pixel in your image.

https://www.rapidtables.com/convert/color/rgb-to-hsl.html

Assuming your RGB values are between 0 and 1 (which is the default in Matlab).

you can do:

L = (max(R,G,B)-min(R,G,B))/2;

Then you can use that for your gray.

R = L;
G=L;
B=L;

And finally, you should plot it in your figure.

About the ratio between "black" and "white" regions. Depends on how you define the threashold.

Ratio = sum(L(L>0.5))/numel(L); % gives you the ratio between 0 and 1. 

You can change your threashold to something sensible, though 0.5 (= 50% white) seems like a sensible value.