Downsampling with Imresize (Satellite Imagery)

Hi,

I am downsampling my satellite images (.png format) with Imresize bicubic function. I would like to decrease the resolution of my images from 2m to 10m. What should I write to scale? Scale of 2 is 0.50. Should I write 0.20 since my scale factor is 5?

Thanks in advance.

Answer 1

[Vinayak Agrawal]

Hi cemre,

Yes, to downsample your satellite images from 2m to 10m resolution using the `imresize` function in MATLAB, you should set the scale factor to 0.20. This is because the scale factor represents the ratio of the output image size to the input image size, where a scale factor of 0.5 results in an output image that is half the size of the input image.

In your case, you want to reduce the resolution by a factor of 5 (from 2m to 10m), so the scale factor should be 0.2 (1/5). This means that the output image will be 20% the size of the input image, or 5 times smaller in both dimensions.

Here is an example MATLAB code to downsample an image from 2m to 10m resolution using `imresize`:

% Load the original image

origImage = imread('original-image.png');

% Set the desired scale factor to achieve 10m resolution

scaleFactor = 0.2;

% Resize the image using bicubic interpolation

downsampledImage = imresize(origImage, scaleFactor, 'bicubic');

% Save the downsampled image to a new file

imwrite(downsampledImage, 'downsampled-image.png');

This code will load the original image, set the scale factor to 0.2, downsample the image using bicubic interpolation, and save the downsampled image to a new file named "downsampled-image.png".

Hope it helps!

Please accept the answer in the case it is correct so that it can help others as well

[Cemre]

Thanks a lot again for your helps. I had resampled my Sentinel-2 image to 2m (RGB bands with 10m spatial resolution each) using resample function in google earth engine before. Is it correct to do the downsampling using these resampled images? I mean, taking the resampled 2m images as input and downsampling it to 10m.

[Image Analyst]

Upsamplining and then downsampling to the original size should produce values that are fairly close, though not exact.

[Cemre]

Thanks for your answer. Best regards.

[Vinayak Agrawal]

Anytime