IMAGES question

I bet all of you uses images at some point in your web/blog/eCommerce etc.

so do i.

Question is : is it OK to harvest image through google images and put it to your blog? is it OK if i post images (taken from some other websites) to my website, or google it considered as stealing and breaking Copyright?

Honestly i have been doing so on all my websites and had no problems with my serps/adsense/copyright laws.

Just out of curiosity is it OK to post someones images on your website?

Gooole is so smart comparing images; i have tried changing image name, tags, properties. Resizing by some percentage, cropping part of it (to change image width/length and ratio), change image visual appearance by putting logo on it. I EVEN tried to make image out of 4 images i harvest on google.

Google finds everything. If you make image out of 4 images - it finds all image part one by one.

One thing that blocked google by finding image is : rotating it by 90-180 percent, But in this case, after rotation not all image will make sense, lol.

So, how you guys doing with images? I know some sources where you can buy images or get for free, but sometimes you niche is so tight that you cant find relevant image in such sources.

sorry for my poor English