convert image to bitmap map image without using for loop

Partition an image into 4 × 4 pixel blocks and

compute average for the block

N1 = N2 = 4
xi = ith pixel

now replace the values to 1 and zero to create a bitmap image.

Without using for loop, how can i write these 2 equations in simple code

Answer 1

[Image Analyst]

Try this:

% Compute mean in 4-by-4 blocks
% kernel = ones(4);
meanImage = conv2(double(grayImage), kernel, 'same') / numel(kernel);
% Compare actual image to mean image.
binaryImage = grayImage >= meanImage;

There will be some errors at the edge of the image where the window does not fit onto the image, like it's only 4 by 3 or whatever. If this is important, then you can use conv2 twice, once to sum the image and once to count the pixels, then divide the gray level sum image from the pixel count image. But usually edge effects are not worth worrying about because they get removed later in the process naturally.