matlab figure saving dim

has anyone observed that if a matlab figure is saved as a jpg, its dimension in the jpg changes. is this true?

I have two images and the description is below :

img A -> .fig size = 638x816x3 || .jpg size = 733x988x3

img B -> .fig size = 638x816x3 || .jpg size = 963x1904x3

it seems that there is some scaling done while saving images as jpg. Further, the scaling doesn't seem to be generalized since the sizes of my .fig files are the same but the output jpgs are different.

Pls explain how to save with same dimensions.

[Ameer Hamza]

How do you determine the size of a file? fig files are not raster images, so they are not stored in the form of pixels. Also, what function are you using to save .jpeg files?

[Anmol Pardeshi]

I determine the size by importing the image on the workspace. As far as the saving method is concerned, I'm using the 'saveas' option from the file menu option. I do acknowledge that if the figure is stored, as jpg, from the code itself, the size remains the same.

Answer 1

[Ameer Hamza]

It seems that you are trying to save an image matrix as a jpeg. saveas() is not the correct function if you want to preserve the resolution of your image. Use imwrite(): https://www.mathworks.com/help/releases/R2020a/matlab/ref/imwrite.html

saveas does not recognize that there is an image present in the figure window. It merely rasterizes all the content of your figure and saves it as an image.

[Anmol Pardeshi]

I speculated something like this. imwrite() should preserve the size because it saves the image "matrix" as it is where as the saveas from the file menu option on the top console should follow some other process of basic image processing & saving.

Thanks fr the prompt and continuous replies, Ameer! Hope you keep safe in the COVID situation.

[Ameer Hamza]

Thanks, and I wish the same for you. I am glad to be of help!