The Image Size Increasing Issue

[baris211]

Hi,

I have a 1.7.5.0 Prestashop based website.

I upload an image on some of my product page which image is 500x500 and 103kb.
After uploading when i go to product page on front office and download this image, the image size 500x500 and 306kb. The image is same, the size is same but the kb increases.

Note: On the Preferences -> Images -> Product Images->large_default sizes are 500x500

If someone has some idea about that issue please make me know.

Thank you in advance!
Baris