Why do the square pixels of a figure change the shape and size after saving?

I try to save or export figures I created in Matlab but the square pixels have different shapes in the saved image. I also tried saving the figure as different imagetypes but I never got an image that has the exact same pixels as the matlab figure. In the first picture you can see a screenshot of the pixels in the matlab figure.

In the second picture you can see a screenshot of the pixels of an exported version of the same figure.

Does anybody know why that happens?

Answer 1

[Image Analyst]

Are you saving it as jpg? The lossy compression algorithm will combine pixels like that. I never use jpg. Try using PNG, which is a lossless compression file format. It will compress the files by a factor of about 1/3 - not as much as jpg but it doesn't alter the picture at all like jpg does.

[Hannes]

I dont save it as a jpg. In this case I saved it as .tif no compression image. but I tried out all different formats. But you are right jpg looks the worst.