Upload an image to Online Image Converter Error

I upload an image(1024 * 600, size 73KB) to online image converter, then the website shows the information below:
" Fatal error : Allowed memory size of 201326592 bytes exhausted (tried to allocate 134217736 bytes) in /web/littlev/littlevgl.com/tools/img_conv_core.php on line 444"

Is there a limit size of an image?

It’s a limit of PHP running on the server.
I suggest trying the offline version:

Can I run the offline version through Windows?

Theoretically yes, but personally I’ve haven’t tried it yet.