How I can generate an image and modify it with Matlab?

Hello,

Is it possible to generate an image with defined row and column numbers without going through the generation of a 2D matrix.

Usually, I created the image according to the following code :

A=3000*ones(200,200);
imwrite(A,['image' num2str(1) '.jp2']);

I want generate an image with 200 rows and 200 columns without generate the matrix A.

My second question, how can I modify an element (the value of a pixel) of an image?

Thank you!

Answer 1

[Kanika Gupta]

Try using this to create a blank image of desired size

blankimage=zeros(200,200)
imshow(blankimage)  

To change value at specific location simply do

blankimage(1,1)=255

[K. Taieb]

Thank you!

It is the same problem, when I generate an image with a large matrix, the matrix size exceeds the capacity of my computer. Like in this example:

blankimage=zeros(50000,50000);
imshow(blankimage) 

[Kanika Gupta]

The maximum size of array supported by Matlab is 10,000. This can be seen

home > preferences > workspace > maximum array size.

If you wish to use it for larger arrays, refer to https://www.mathworks.com/help/matlab/matlab_prog/resolving-out-of-memory-errors.html

Answer 2

[Image Analyst]

Use the uint16 option in ones to cut down the size by a factor of 4. If you use ones() without it, you're using floating point values and have 8 bytes instead of 2 bytes and uint16.

A = 3000 * ones(200, 200, 'uint16');
imwrite(A, 'image1.jp2');