Save file.bmp from a matrix.

Dear all,

I am quite new in Matlab and I am eperiencing some issue by saving a matrix as an image.

I have a matrix (202 x 134 double) composed of 0 and 1. I want to generate a black and white image from that.

If used: imshow(mymat), and I save the file from that it is perfect; but I have to save images within a loop.

I tried to use:

imwrite(mymat,sprintf('FIG%d.bmp',z1))%,'Quality',100)

But the quality of the image is very very low as you can see from the attached pictured.

I tried also to use:

image = mat2gray(mymat,[0 1]);
imwrite(image,sprintf('FIG%d.bmp',z1))

But I get the same result.

Thanks in advance.

[Rik]

202x134 is a fairly low resolution already, but the file you uploaded is 67x101.

Can you confirm that size(mymat) returns [202 134]?

I would suggest avoiding image as a variable name, as that is already a base Matlab function/class.

[Michele Vanini]

Yes sorry I made a mistake, size(mymat) is [101 67].

Thanks for your suggestion, I did it but the result is still the same.

I attach here the Matlab script, too. Do you have some suggestions to solve this? Maybe a different way to save the figure such as with saveas? But since I have only a matrix and not a figure I don't know how to implement it.

[Rik]

How did you get the idea you have a 202x134 matrix? Nothing so far indicates that. Using a different function will not fix anything if your input data is not what you expect.

[Michele Vanini]

Because in the script above I changed the value of d from 1 to 0.5 and obtained a 202x134 matrix. With d = 1 I obtain a 101x67 matrix which is the one used to generate the image.

Answer 1

[Image Analyst]

In your code, you save the image as JPEG - that's probably why it's blurry. Never use JPG for image analysis.

        %save image as jpeg
        imwrite(image_rotated,sprintf('FIG%d.jpeg',z1),'Quality',100); % will create FIG1, FIG2,...

Cast it to uint8 and Save it as PNG and it should be fine.

% Save image as PNG.
baseFileName = sprintf('FIG%d.PNG', z1);
fullFileName = fullfile(pwd, baseFileName);
fprintf('Saving image file : "%s".\n', fullFileName);
imwrite(uint8(image_rotated), fullFileName); % Will create FIG1, FIG2,...
fprintf('Success! Done saving image file.\n')

The saved/recalled image will be the same size as image_rotated.

Dont' use image as the name of a variable since that's the name of a built-in function.