projecting a circular image onto a hemisphere with bumps according to a mask

i've a 1000x1000 rgb image of a retina. i want to wrap it onto a hemisphere 1st of all. secondly, i've a masking layer corresponding to the rgb image (also 1000x1000). i want the hemisphere to have to bumps (radius slighty greater/less than normal) for the areas dictated by the mask.

Answer 1

[Yatharth]

Hi,

I understand you are trying to map a 2D image to a hemisphere and then create bumps on the same sphere based on the mask you want to input.

You can create a sphere using the sphere function and with the help of interp2 function you can wrap the image to the sphere. For the bumps you can create a simple bump map using the mask coordinates.

Here's an example how you can achieve it

rgbImage = imread('retina_image.jpg'); % Replace with the path to your image
mask = imread('mask_layer.jpg'); % Replace with the path to your masking layer
grayImage = rgb2gray(rgbImage);
[x, y, z] = sphere(100);

radius = 500; % Adjust as needed

maskThreshold = 128; % Adjust as needed
bumpMask = mask > maskThreshold;

bumpHeight = 10; % Adjust as needed
bumpRadius = 550; % Adjust as needed
bumpMap = zeros(size(x));
bumpMap(bumpMask) = bumpHeight;

x = x * radius;
y = y * radius;
z = z * radius;

wrappedImage = interp2(double(grayImage), x, y);
wrappedImage = wrappedImage + bumpMap;

figure;
surf(x, y, z, wrappedImage, 'EdgeColor', 'none');
colormap(gray);
axis equal;

The interp2 function in MATLAB performs 2-D interpolation to estimate values between existing data points. In the context of wrapping an image onto a sphere, interp2 is used to map the grayscale image onto the surface of the sphere. You can read more about the interp2 function from here and creating a sphere from here