Are there any API's that'll let me search by image?

I have an image and I want to 开发者_如何学Csearch to see what it is. Any API's available for that?

I believe there are quite a few. You want to search for Content-based Image Retrieval (CBIR). Wikipedia has a page of CBIR engines, including an extensive list of open source ones. For example, isk-daemon and LIRE are both open source CBIR libraries:

isk-daemon is an open source standalone server and library capable of adding content-based (visual) image searching to any image related website or software.

The LIRE (Lucene Image REtrieval) library provides a simple way to retrieve images and photos based on their color and texture characteristics.

Another one is fire it's GPL and they use the Magick++ libraries.