Image upload problem (create more image than it needs)

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When I upload product images, I set up 3 image sizes for products. Butr there are other image sizes are in the system, for categories etc.  When I upload products via import, make all of the image sizes whick are in the system and generete jpg and png as well at the same time, but I only need jpg.

 

Example, in import csv:

mysite.com/img/products/product1.jpg

 

It needs to generate these files:

 

mysite.com/img/p/1/1/product1.jpg

mysite.com/img/p/1/1/product1_home.jpg

mysite.com/img/p/1/1/product1_cart.jpg

mysite.com/img/p/1/1/product1_thickbox.jpg

 

But now, it is generating the following:

mysite.com/img/p/1/1/product1.jpg

mysite.com/img/p/1/1/product1.png

mysite.com/img/p/1/1/product1_home.jpg

mysite.com/img/p/1/1/product1.png

mysite.com/img/p/1/1/product1_category_default.jpg (category_default is not available for products, only for categories)

mysite.com/img/p/1/1/product1_category_default.png

 

3-4x more images will be generating. What can I do?