Map Colors in Photoshop Elements 10
Elements provides color mapper commands that change the colors in your image by mapping them to other values. You find the color mappers on the Filter→Adjustments submenu.
Here is an example of each command, all of which are also briefly described in the following list:
Equalize. This mapper first locates the lightest and darkest pixels in the image and assigns them values of white and black. It then redistributes all the remaining pixels among the grayscale values. The exact effect depends on your individual image.
Gradient Map. This command maps the tonal range of an image to the colors of your chosen gradient. For example, colors (such as orange, green, and purple) are mapped to the shadow, highlight, and midtone areas.
Invert. This command reverses all the colors in your image, creating a kind of negative. Black reverses to white, and colors convert to their complementary hues. (Blue goes to yellow, red goes to cyan, and so on.)
Posterize. This command reduces the number of colors in your image. Choose a value between 2 and 255 colors. Lower values create an illustrative, poster look, and higher values produce a more photo-realistic image.
Threshold. Threshold makes your image black and white, with all pixels that are brighter than a value you specify represented as white, and all pixels that are darker than that value as black. You can change the threshold level to achieve different high-contrast effects.