The users are asked to find desired images in our system and the other two image search engines. For each task, the users may formulate different queries and use the existing search options supported by the image search engines. For each search engine, we define one unit of operation as performing any interaction so that the search results are refreshed. Ideally, our image search system can combine the search options, existing in Google and Bing image search engines, but in the experiment, users only conduct the color map option and change the text query. When users use Google and Bing image search engines to search images, they can use different text queries, and use the color related search options and similar image search options. Submitting a new text query, or clicking a search option to get a new search result, is viewed as a unit of operation. In our system, either submitting a novel target color map, or submitting a new text query, is one unit of operation.