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

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muhammad afiq
muhammad afiq 2020-6-17
评论： Ameer Hamza 2020-6-17
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.

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回答（2 个）

Ameer Hamza
Ameer Hamza 2020-6-17
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?
Benoit Espinola
Benoit Espinola 2020-6-17
编辑：Benoit Espinola 2020-6-17
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.

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